Suspension 101

[Predator36]

Notice the header is suspension 101 - not shocks 101. Many times shocks are blamed for bad setup, bad a-arm and/or swingarm geometery. However that does not make the shocks any less important. Please limit all questions and comments to this forum. Please no PM or e-mails. First we will measure the bike. As we go along with measuring the bike feel free to ask for photos if you do not understand. Also any one wanting to help by providing photos would be greatly appreciated. Some of the measurments are very simple but I will limit them to a max of one per day. I will use a stock 400ex for this setup.

[Predator36]

First measurment is wheelbase. That is from the center of the rear axle to the center of the front wheel. My bike is 49 inches. This measurement will later be refered to only as WB. Since the rear axle moves forward and back when you adjust the chain - each bike may be differant even with the same componants.

WB=49

[QuadRacer041]

very good topic to dicuss, alot of people will get some good info out of this.
just curious, who are you?how many years of quad experiance to do you have. not trying to test you or be a wise ***** im just curious

[Predator36]

Originally posted by quad041
how many years of quad experiance to do you have.

Not very many. Quads have only been around since 1985. I first rode and played around with three wheelers. My oldest one was a 1970. Some people think 3 wheelers are dangerous but they are loads of fun.

[Dave400ex]

Yeah I was trying to figure out who he was too. In all of his posts he seems very smart and has great info. Glad to have you! This thread will help out a lot of people.

[B@ckBoneBelgium]

could we please continue .... he said 1 measurment a day and not a week :D :cool:

Please carry on with the project ?

[Quadfather]

:huh I don't get it.

[Predator36]

Originally posted by B@ckBoneBelgium
could we please continue .... he said 1 measurment a day and not a week :D :cool:

Please carry on with the project ?

Sorry - out of town for the weekend, will continue on monday A.M.

[Predator36]

Next measure the distance from the center of the rear axle to the center of the foot pegs. My bike is 18 inches. This can vary on each bike the same way as the WB measurement.

ATP = 18

Recap:

WB = 49
ATP = 18

[Predator36]

Now weigh the rider. That is with all the gear that is worn when riding. I am 180# now with gear.

RW = 180

Recap:

WB = 49
ATP = 18
RW = 180

[Predator36]

The next measurements will require you to remove all the shocks. For measureing I prefere two - twelve inch blocks and 2 1.5 inch blocks.

[QuadRacer041]

Originally posted by Predator36
Next measure the distance from the center of the rear axle to the center of the foot pegs. My bike is 18 inches. This can vary on each bike the same way as the WB measurement.

ATP = 18

Recap:

WB = 49
ATP = 18

:confused: , do u mean measure from the right axle hub bolt to the right foot peg?or from the center of the carrier on an angle to the right foot peg?

[Predator36]

Originally posted by quad041
:confused: , do u mean measure from the right axle hub bolt to the right foot peg?or from the center of the carrier on an angle to the right foot peg?

Keep your tape measure both parallel to the ground and to the centerline of the quad. What I did was hold the tape across the foot peg, sticking back, with the end about 2 inches above the rear axle. You can either place a builders square on the ground or sight straight down to find the center of the rear axle.

What we need to know is the relationship of the riders weight to the wheel base. If it were in the center - than a 150 rider would be placing 75#on the front and 75# on the back. With my pegs at 18 inches ATP I have a lot more of my wieght on the back. I am not staing that this is good or bad - I just need to know how much of my wieght is on the front and the back.

[Predator36]

For the next set of measurements there are several things that are very critical.

1. You must be on an even floor.
2. You must have the correct pressure in your tires for your type of riding. Minimum in the rear - 5 lbs, 10 prefered. Front - 10lbs, 15- 20 prefered. I am not here to argue about tire pressures but incorrect pressures will get bad readings and low pressures will cause problems when riding. If your application and or likes dictate lower pressures - you may need to adjust for this when taking measurements RCSL and FCSL.
3. You must have the tires and wheels on the bike that you plan to use. I see a lot of guys switch tire size and base there likes and dislikes of a tire without adjusting the bike setup to match the tires.
4. Front wheel offset is also very critical as differant offsets change the leverage on the shocks.

Now place a 12 inch stand or box under the frame at both the rear (footpeg area) and in the front (just behind the a-arm mounts)

This will be where we setup the extended length of the suspension.

If you are setting up a desert racer or have a custom linkage setup you may want to use a higher setting. For TT I use 8 inch blocks, desert - 13 inch blocks, Flat track only - 7 inch blocks.

Remove all your shocks and measure the center to center distance of the shock mounting holes. My 400ex is 16 3/8 inches in the front and 15 1/4 in the back.

Check for any problems at this point - turn front end side to side watching for anything binding. Are the tires touching the ground??if not find out why and solve the problem.

My front end is fine - FESL (Front Extended Shock Length) = 16 3/8 inches

My rear is not OK - If I leave it as it is , it will be out of balance with the front. My shock fully extended in the rear is 15.5 inches long and not wanting to shorten the travel I want it to be 15.5 inches at 12 inches (frame height). To solve this I can build a new swingarm with the linkage mount relocated or install a lowering strut. I will order a lowering strut today - install it, adjust it till the correct extended shock length is acheived before I can continue with this.

Recap:

WB = 49
ATP = 18
RW = 180
FESL = 16 3/8
RESL = Must be repaired before I continue.

[QuadRacer041]

if im understanding you right . your .25 out in the rear?that is why your using a lowering strut????

[Predator36]

Originally posted by quad041
if im understanding you right . your .25 out in the rear?that is why your using a lowering strut????

That is correct. I use lowering struts on a lot of bikes to get the setup correct.

[Predator36]

Santa has a new job for the off season. He drives a little brown truck with UPS on the side. I have just recieved my Durablue adjustable link for the back and hope to install it tonight.

[Predator36]

I just installed my adjustable link in the back and adjusted it so that with the frame 12 inches of the ground the rear shock mounting holes are 15.5 inches on center.

RESL = 15.5

Recap:

WB = 49
ATP = 18
RW = 180
FESL = 16 3/8
RESL = 15 1/2

[Predator36]

The next measurement may need to be adjusted for those who want to run low tire pressure. Next place 2x4's flat on the ground under the frame. That sets the frame 1.5 inches off the ground. Now go over the front and back looking for any thing that will bind. Rear is fine. Front tie rods now hit the frame when turning right or left. If I dont adjust for this I run the risk of bending tie rods. I adjust for this by adding a one inch steel block to the 2x4 making the frame now 2.5 inches off the ground. I again check for any problems. All clears now. This is the point where the shocks need to bottom out (metal to metal contact). Now measure the center to center distance of the shock mounts. Fronts are 11 5/8 and rears are 10. 3/4. FCSL (Front compressed shock length) = 11 5/8. RCSL = 10 3/4.

Recap:

WB = 49
ATP = 18
RW = 180
FESL = 16 3/8
RESL = 15 1/2
FCSL = 11 5/8
RCSL = 10 3/4

[Predator36]

First problem we ran into was the fact that the rear dropped away further than the front. At first glance this may not seem important but when riding a bike like this you will notice that the back will buck more over small kicker bumps - still no big issue. Worst problem is in a down hill rough terrain conditions the back end will feel like it is swapping from side to side and also feels like it wants to kick you over the bars.

[Predator36]

Second problem was the fact that the physical parts on the bike will not allow us to go lower than 2 1/2 inches frame height when bottomed out. This is not a big issue as long as the shocks are set for this. If the front shocks commpressed length is shorter (ignore the bottoming bumper) 11 5/8 we run the risk of breaking parts in aggressive riding conditions. You can measure the front shock length on the bench by taking the center to center length and subtracting the exposed shaft length. To measure the exposed shaft length you need to slide the bumper down so that you can see both ends of the shaft - at the body and at the eye or spring retainer. If the compressed length is to short you will need a longer body or an external spacer.

[Predator36]

From previous measuremants I have determined that my front shocks must have an extended length of 16 3/8 inches and a compressed length of 11 5/8 inches. I measured my new shocks and found that they have an extended length of 16 1/2 inches. To correct this I dissassembled the front shocks and added a 1/8 inch spacer between the seal head and the piston. The commpressed length is 10 3/4 inches. To correct this I installed a 7/8 inch spacer between the bumper and the bottom of the shock. Unless you have the tools and knowledge to work on shocks - these are things you need to have your shock guy do for you. He will think you are being to picky but since you are paying him - whatever. Also dont expect your shock company to build your shocks to this length unless you supplied them with all the correct measurements or they measured the bike and fit the shocks to it. There are to many combinations of tires, wheels , a-arms, swingarms and etc. for the shock company to match every bike unless they have all the details.

Now my front shock travel is in the correct range and I need to match the rear as close as possible to this.

[465Stroker]

When measuring your RCSL and FCSL are you doing this with the bumpers off of the shocks? I know my PEP's bumpers are made to squish to an 13/16" under full load.

[Predator36]

Originally posted by 465Stroker
When measuring your RCSL and FCSL are you doing this with the bumpers off of the shocks? I know my PEP's bumpers are made to squish to an 13/16" under full load.

Yes, that measurement is as if there was no bumper (metal to metal) That gives you maximum protection in extreme conditions against breaking parts and more protection from the frame hitting the ground. You realy dont want the bike to go that low and before it does - the bumper adds a lot off additional bottoming resistance.

400ex rear shocks - I have seen a lot of proof of metal contact on both the stock and PEP (Fox) rear shock. On the PEP and Works fronts I have seen the bumpers split in half on extreem conditions.

[Predator36]

If the compressed length is correct - not only do you avoid as many broken parts but you are letting the bottoming bumper do its job as part of the active suspension.

[465Stroker]

Let's keep going! I am still concerned about the frame hitting the ground under full load. Are we taking tire flex into consideration? I race XC, so will I need to figure more frame to ground clearance since my tire to rim clearance is around 4.5"? I do now that my rims are very close to bottoming and pinching the tire on large jumps - especially the rear.
I do understand that my XC setup will require a shorter shock body than an MX setup since we run larger tires- correct?

[Predator36]

Originally posted by 465Stroker
Let's keep going! I am still concerned about the frame hitting the ground under full load.

That is a very important issue. I see a lot of bike/shock setups that have too short a compressed shock length - letting the frame hit the ground easily , even when landing on a flat surface.

[Predator36]

Originally posted by 465Stroker
Are we taking tire flex into consideration? I race XC, so will I need to figure more frame to ground clearance since my tire to rim clearance is around 4.5"? I do now that my rims are very close to bottoming and pinching the tire on large jumps - especially the rear.

Not yet, I have only mentioned it in regards to tire pressure. Once the bike is fully measured and balanced (front to rear) then overall adjustments must be made to account for this. I may need to backtrack on a few issues later but once the initial setup is done I would like to address varying conditions and needs.

Examples of conditions that need to be adjusted for:

Low tire pressures - XC racing
Large riders, say 6'5" with atv bend bars - Weight will not be distributed like a 5'8"rider with CR bars.
Low setups that still do big jumps - Pace/indoor racing.

[Predator36]

Originally posted by 465Stroker

I do understand that my XC setup will require a shorter shock body than an MX setup since we run larger tires- correct?

Yes, if thats what it takes to get the correct extended and compressed lengths.

[Martin Blair]

I dont know if im getting this at all but is the whole goal to get the rear end and front end to drop to the same level, so when the quad is lifted stright up both of ur tires are in the same horizontal plane, if u understand math, or at the same level off the ground? thanks.

[Predator36]

Originally posted by HN400exracer
I dont know if im getting this at all but is the whole goal to get the rear end and front end to drop to the same level, so when the quad is lifted stright up both of ur tires are in the same horizontal plane, if u understand math, or at the same level off the ground? thanks.

This is one step in the "whole goal". First we want the front and back to work together. Yes, if the quad is lifted up the tires would be on the same horizantal plane.

[Martin Blair]

Ok and you find this out buy all the explain measurements, if it is off where do u get adjustible linkage kits? i looked on durablues website and couldnt find anything.

[Predator36]

Originally posted by HN400exracer
Ok and you find this out buy all the explain measurements, if it is off where do u get adjustible linkage kits? i looked on durablues website and couldnt find anything.

Anyone that sells Durablue parts can sell you a rear link for a 400ex. Nac's and many others.

[86atc250r]

I'm kinda late entering this thread but would like to clear up something mentioned earlier....


4. Front wheel offset is also very critical as differant offsets change the leverage on the shocks.

Front wheel offset does not affect leverage against the shocks because it does not modify travel.

In order for the leverage to increase/decrease against the shock, the wheel travel per unit shock travel ratio must also change. Wheel offset does not affect this ratio since it is not moving the shock mount's position in relation to the control arm pivot points.

However, offset does significantly affect scrub and the leverage of the terrain against the end user (as transmitted thru the tie-rods to the steering stem to the handlebars).

[TRXR29]

Predator36: Why is it so important that the wheels be on the same horizontal plane both bottomed out and topped out? That's not a bad thing, but I doubt it's really critical. Look at the top MX bikes, most of them have significantly different vertical wheel travel front to rear. I don't see why you are going to such lenghts to make the wheel travel exactly the same.

[Predator36]

Originally posted by 86atc250r
I'm kinda late entering this thread but would like to clear up something mentioned earlier....



Front wheel offset does not affect leverage against the shocks because it does not modify travel.

In order for the leverage to increase/decrease against the shock, the wheel travel per unit shock travel ratio must also change. Wheel offset does not affect this ratio since it is not moving the shock mount's position in relation to the control arm pivot points.

However, offset does significantly affect scrub and the leverage of the terrain against the end user (as transmitted thru the tie-rods to the steering stem to the handlebars).

Thank you for that clarification. I do setups on single a-arm suspension as well as dual a-arm (like a 400ex). I should have pointed that out.

Also thank you for taking an interest in this thread. I will be addressing a problem in the rear shock travel of a 400ex next but following that I could use your input on shock spring selection and design. Some of the measurements we have been taking will lead up to a very critical setup issue regarding spring rate and race sag.

Also - hint hint - a program written in VB6 to bring this all together would be cool.

[Predator36]

Originally posted by TRXR29
Predator36: Why is it so important that the wheels be on the same horizontal plane both bottomed out and topped out?

So that the front and back work together.

[Predator36]

Originally posted by TRXR29
Predator36: Why is it so important that the wheels be on the same horizontal plane both bottomed out and topped out? That's not a bad thing, but I doubt it's really critical. Look at the top MX bikes, most of them have significantly different vertical wheel travel front to rear. I don't see why you are going to such lenghts to make the wheel travel exactly the same.

I understand your doubts - and you are correct that many of the top MX bikes would not pass this setup with flying colors. There are a few that do. You may then ask - do I think I know more about setup than the Pros - NO. One thing that seperates the pros from amaturers is their ability to convey to their mechanic what needs changed on the bike. Tim Farr and Bill Balance are masters of this. Not only can they ride well but they understand how a bike works and when things are wrong they have a good idea how to fix it.

Wheel travel exactly the same?? I wish - the next thing I will address is the rear shock on the 400ex. It does not have the travel that I need to match it to the front and because of this we will need to compromise on what could be a better setup. This problem has been addressed in differant ways by differant companies.

This thread is getting better everytime I check it :)

One thought or suggestion: Much of this seems aimed to the stk ex suspension (well not all but anyhow) and should there be any additional info or problems related to the Long travel (19") front set ups or aftermarket rear shocks or even rear LT set ups?

Just want to be sure as to any possible changes to the measurements on the other stuff out there and since I have the LT fronts and will not be able to get started measuring it up for another week or so.

[Dave400ex]

This thread is great! Keep it up.....

[86atc250r]

Predator-

Spring info:
You know how to get ahold of me, or I can post my thoughts here if you like (if it pertains to any of the upcoming info).

As far as a program, I would certainly be willing to write a little code if I know what we're looking to input, calculate, and output.

[Predator36]

Originally posted by 440EX4me
One thought or suggestion: Much of this seems aimed to the stk ex suspension (well not all but anyhow) and should there be any additional info or problems related to the Long travel (19") front set ups or aftermarket rear shocks or even rear LT set ups?



The rear LT setups are a big help in proper setup on the 400ex as you will see when I address my next dilemma.

Front LT setups???? More an issue of brand, parts, and balljoint angles. I have seen socalled LT fronts that that only have 9 inches of usable travel.

[Predator36]

If you look at the measurements regarding the rear that I took earlier. RESL 15 1/2 and RCSL 10 3/4 you will see that I want my rear shock to be 15 1/2 inches long extended and 10 3/4 inches long compressed. Oops - the stock rear shock will only compress to 11 1/4 inches long. The stock rear shock only has 4 1/4 inches of travel at the rear shock. To match the rear to the front I would need a shock with 4 3/4 inches of travel at the shock.

There are several solutions (or bandaids) for this problem. One of the cheaper ones is - Inside the shock there is a big washer that acts as a backing plate for the compression valving. It is also what contacts the internal bumper when fully extended. I will machine a stepped washer to replace it that will let the shock extend an additional 1/8 inch. I now have 4 3/8 inches of travel at the shock. My shock extended length is now 15 5/8 inches long. I now place my quad back on the 12 inch blocks and adjust the Durablue adjustable link till the RESL (rear extended shock length) is 15 5/8 inches. Back on the 2 1/2 inch blocks my RCSL is now 10 7/8 inches. My shock still does not have the travel that I want so I now need to split the differance and readjust my linkage so that I have 15 5/8 inches RESL with the frame 11 5/8 inches of the ground and 11 1/4 RCSL with the frame 2 7/8 inches of the ground

CRESL (corrected rear extended shock length) is 15 5/8
CRCSL (corrected rear compressed shock length) is 11 1/4

Recap:

WB = 49
ATP = 18
RW = 180
FESL = 16 3/8
RESL = 15 1/2
FCSL = 11 5/8
RCSL = 10 3/4
CRESL = 15 5/8
CRCSL = 11 1/4

[forum]

moving the shock mount further along a arm???
Ok if the shock mount on the a arm was moved out toward the tire would this cause any problems?? of course the leaverage would change and my shock builder would have to know this in order to build the shocks corectly but i was wondering about other problems.

this was a post i posted earlier but i thought i'd move it in here so you'd see it.

[Predator36]

Originally posted by forum
moving the shock mount further along a arm???
Ok if the shock mount on the a arm was moved out toward the tire would this cause any problems?? of course the leaverage would change and my shock builder would have to know this in order to build the shocks corectly but i was wondering about other problems.



Moving the shock mount in or out from the normal position will quickly test your shock builders technical knowledge.

Lets look at it from a big change. My 400ex that I measured and am setting up for this example has a front tire travel of 9.5 inches with a shock travel of 4.75 inches. That is an overall ratio of 2/1. Yes the ratio changes thru the travel but not much (that is the advantage of using linkage). If we were to move the shock mount out far enough till we had a 1/1 ratio the shock would need half as much compression valving or less (due to additional friction and increased velocity) and half as much spring pressure. With the lighter spring you would need to have your rebound valving about half as stiff. However you would need a shock that has 9.5 inches of travel(can you say Polaris) to have your suspension work the same. All this is not to say that it would be good or bad but to help you understand how it all works together.

One a-arm builder that I know will move the shock mount out for his customers if they want wider a-arms but dont have the money for new shocks. When he does this the suspension looses travel but remains stiff enough to be usable.

[boogiechile]

quote:
--------------------------------------------------------------------------------
Originally posted by 86atc250r
I'm kinda late entering this thread but would like to clear up something mentioned earlier....



Front wheel offset does not affect leverage against the shocks because it does not modify travel.

In order for the leverage to increase/decrease against the shock, the wheel travel per unit shock travel ratio must also change. Wheel offset does not affect this ratio since it is not moving the shock mount's position in relation to the control arm pivot points.

However, offset does significantly affect scrub and the leverage of the terrain against the end user (as transmitted thru the tie-rods to the steering stem to the handlebars).
--------------------------------------------------------------------------------



Thank you for that clarification. I do setups on single a-arm suspension as well as dual a-arm (like a 400ex). I should have pointed that out.

************************************************


I think I disagree here. True that wheel offset will not affect the motion ratio but it will change the leverage on the shock. Think of it this way, if you took a frt hub off and put a ten foot long peace of pipe over the spindle, then raising the pipe from its end would make it much easier to compress the shock. While all the time the motion ratio had not changed. If you put on a wheel with an offset ten foot to the outside it would be the same as having the pipe on. While not as dramatic a wheel with a 2-3 offset is going to put more leverage on the shock then a 4-1 offset wheel. Does this not make sense? Help me out if I'm wrong.

[86atc250r]

Think of it this way, if you took a frt hub off and put a ten foot long peace of pipe over the spindle, then raising the pipe from its end would make it much easier to compress the shock. While all the time the motion ratio had not changed.

Actually, it would not, that would violate the laws of physics.

Using your example, a wheel with a ridiculously exaggerated 10' offest would not put more stress against the shock, however - it would put more stress against the ball joints and spindle.

The only way to put more stress against the shock would be to extend the pivot point (move the ball joints 10' out) while leaving the shock mount in the same position.

Try the experiment (actually, don't, you'll likely bend the spindle as it will try to become the pivot point)

Negating the effects of the pipe's flex, the force required to move the control arm assembly "X" distance will be the same as if you directly grabbed the spindle with your hand.

Since the distance you move the pipe and the distance the spindle will move will be the same (again, assuming the pipe is strong enough not to flex), no leverage is applied and the force required will also remain the same, regardless of how long the pipe attached to the spindle is.

Now, if your pipe was directly connected to the lower control arm (without the pivot of a ball joint), the results would be different since you would move the pipe a long distance to move the control arm a short distance.

Making sense?

[R-Crazy]

you all must be math wizards. i like all this, but could never figure it out. maye someone could give a PM about some of the equations you are using.

dave

[boogiechile]

86atc
yea, you're right. that makes perfect sense. I really had to of known that and just got a brain fart. It's as clear as a bell now and should have always been.
Thanks

[TRXR29]

Wow, I'm glad we got that whole leverage ratio/ wheel offset thing resolved. I was about to suggest somone be hit on the head with this theoretical 10 foot pipe! :)

Anyway, I'd like to consider the whole equal suspension travel thing in a little more depth. Predator36, I'm not arguing, but since you are posting all of this information I feel that someone should step up with a slightly opposing view. While I agree with a lot of what you have said, I disagree about the benifits of similar or equal front and rear travel.

Modern motocross dirtbikes have incredible suspension, generally better than any of the top ATVs. The Yamaha YZ250 is recognized as one of the best, so I'll use it for an example. Claimed suspension travel is 11.8" front and 12.4" rear. Keep in mind, however, that the front fork is raked back 26 degrees. Wheel travel involves both vertical and horizontal movement. If I did my math right, the ends up with 8.39" of vertical wheel travel and 3.41 horizontal wheel travel. With the rake of the a-arms, a quad will, to a lesser extent, experience the same phenomenon.

Rear travel is a bit harder to figure, but you get a vertical number much closer to the stated number because of the wheel path. I have to assume the stated wheel travel is measured along the arc of the wheel, not vertically. Even if it is measued vertically, that just reinforces my point. I'm not really great with geometry, and I don't have a completely accurate swingarm length number. Still, using a swingarm length of 20" (pretty close) and if I did the math right I get a true vertical rear travel of 11.78"

Front travel: 8.39" Rear Travel: 11.78" Difference: 3.39" or about 28%

YZ250s have great suspension, and it's not because front and rear wheel travel is the same, or even close. Not to say that having similar wheel travel front to rear is bad, it's just that the benifits are probably not there. Anyway, good luck, and thanks for making us all think a little bit. If anyone has a different opinon, please post it, I'd love to learn something.

[Predator36]

Originally posted by TRXR29
Modern motocross dirtbikes have incredible suspension, generally better than any of the top ATVs. The Yamaha YZ250 is recognized as one of the best, so I'll use it for an example. Claimed suspension travel is 11.8" front and 12.4" rear. Keep in mind, however, that the front fork is raked back 26 degrees. Wheel travel involves both vertical and horizontal movement. If I did my math right, the ends up with 8.39" of vertical wheel travel and 3.41 horizontal wheel travel. With the rake of the a-arms, a quad will, to a lesser extent, experience the same phenomenon.



Front travel: 8.39" Rear Travel: 11.78" Difference: 3.39" or about 28%

YZ250s have great suspension, and it's not because front and rear wheel travel is the same, or even close. Not to say that having similar wheel travel front to rear is bad, it's just that the benifits are probably not there. Anyway, good luck, and thanks for making us all think a little bit. If anyone has a different opinon, please post it, I'd love to learn something.

Modern dirt bikes have great suspension - no kidding - if only they made quads with that kind of suspension.

YZ 250 front wheel travel - I have a yz250 here - the rake only looses about an inch of vertical travel and not the 3+ inches that you mentioned. Draw a line on something like a desktop at 26 degrees and measure how it effects vertical travel and you will see what I am talking about.

If I had more travel on one end of the bike - I would have more travel in the back. My MX quad has a swingarm shock combo that I designed. I have played with lots of combinations and I prefere the currant setup of 10.5 inches in the front and 11.5 inches in the rear. The problem with the 400ex is the lack of usable travel in the rear. I have tested with up to 16 inches in the front (yes it can be done with +4 and Protrax parts) and 14 inches in the back (this with cr linkage).

All the wheel travel measurements used in this setup are vertical numbers.

[forum]

.. What if i were to run 20 inch holeshot mx's on the front instead of 19's will this let me shock builder (elka) give me more travel

[Predator36]

Originally posted by forum
.. What if i were to run 20 inch holeshot mx's on the front instead of 19's will this let me shock builder (elka) give me more travel

Larger diameter tires will not gain you any travel. However I have seen a-arms that had the ball joints welded in at angles that did not place the travel in the correct range and a differant tire diameter may help to move the travel into a better range giving you more usable travel.

Example: In May 2002 I measured a MX quad that when placed on 1.5 inch blocks (under the frame) I could lift up on the tire wheel assembly another 2 inches before there was any bind in the ball joints. When placed on 12 inch blocks this same quad had the ball joints bind up while the tires were still an inch off the ground. With +3 a-arms this bike only had 9.5 inches of usable travel. By installing larger tires and adjusting the shocks to bottom at the correct length I was able to increase the usable travel to 10 inches.

Many times the parts that are available are less than ideal. Had these Ball joints been welded in at a steeper angle this front end could have had up to 11.5 inches of travel.

[Predator36]

Next measurement: Weigh the bike. Nice setup is the 4 pad setup that they use on go karts. I dont have that so I use a bathroom scale and 3 blocks the same thickness as the scale. I place a block or scales under each tire and then rotate the scales around the bike till I have the weight at each tire. A freind of mine simply uses 4 scales at once. My front end weighs 99 lbs at each tire. FTW (front tire weight) = 99. My rear end weighs 104 lbs. at each tire. RTW = 104.

Recap:

WB - 49
ATP - 18
RW - 180
FESL - 16 3/8
RESL - 15 1/2
FCSL - 11 5/8
RCSL - 10 3/4
CRESL - 15 5/8
CRCSL - 11 1/4
FTW - 99
RTW - 104

[Predator36]

Originally posted by 300ex rules
you all must be math wizards. i like all this, but could never figure it out.

dave

Sorry to dissappoint you but this is all just measurements. The math is just ready to start. I will give all the equations with only a brief explanation of them. Feel free to ask questions. The measurement and equations are important but equally important is understanding how it all works so you can apply it to your situation and make adjustments to it where you disagree with my setup.

I will show you how I setup a bike (not that that is the best) and hope thru that you will be more informed about the dynamics of suspension.

[Sick0]

I think Forum was trying to say if he went to bigger tires he could adjust his shock for more travel.

[Predator36]

Originally posted by Sick0
I think Forum was trying to say if he went to bigger tires he could adjust his shock for more travel.

Only if the larger tires helped to solve an a-arm geometry problem. Otherwise - no.

[forum]

I hate to say your wrong but i think you can. Since the tires are larger the a arms can go up higher before the frame hits the ground. is this not true?? of course my shock builder would have to no this to gain any more travel in the front end

[TRX_Thumper]

yeah thats true but it would require a custom shock that has more travel built in....and it wouldnt be much of a gain maybe what an 1nch at the most..i dont even know if you could buy a shock designed for that..at the same time a taller tire will also bounce off your fenders more easily
......its not worth it is what im sayin

[Predator36]

One more thing that I need to add to the list of measurements is the height that the frame was off of the ground when I took the extended and compressed shock length measurements.
BFH (bottomed frame height) 2 1/2 inches. That is the height of the blocks that I had under the frame when I took the measurments FCSL and RCSL.
EFH (extended frame height) 12 inches.

Recap:

WB - 49
ATP - 18
RW - 180
FESL - 16 3/8
RESL - 15 1/2
FCSL - 11 5/8
RCSL - 10 3/4
CRESL - 15 5/8
CRCSL - 11 1/4
FTW - 99
RTW - 104
BFH - 2 1/2
EFH - 12

[Predator36]

The foundation of any suspension system rests on the springs. If they are incorrect or do not work together we end up adjusting other things to bandaid a problem that stemmed from using the wrong springs. We have now looked at some of the limitations of the parts that we have to work with (not enough travel in the back) and adjusted to the best possible with what is available. Now we need to determine if the front and rear springs are the correct rate and if they are working together. Watch a bike or quad in a G out situation such as the face of a big jump. Most modern dirt bikes will compess the front and back equally since everything is working together. A lot of quads in this same situation will not. This is mostly due to poor spring selection.

Example : A soft rear spring can land a big jump with out bottoming if the compression valving is stiff enough. But in a G out situation may bottom out easliy. When this happens the bike will bottom out and then kick up in the rear causeing the bike to jump poorly.



Originally posted by Predator36
[B


WB - 49
ATP - 18
RW - 180
FESL - 16 3/8
RESL - 15 1/2
FCSL - 11 5/8
RCSL - 10 3/4
CRESL - 15 5/8
CRCSL - 11 1/4
FTW - 99
RTW - 104
BFH - 2 1/2
EFH - 12 [/B]

The following formulea will give us a desired calculated spring rate for a single spring setup in the front. Dont get to excited yet if it is not the number you like as calculated spring rate may be differant than your spring rating. I will later give you all the info needed to calculate spring rate. I will also after that address how the spring rate must be changed for excess sag (multi spring) setups simaler to the modern quad shocks from PEP, Axis, and Elka to provide appropriate bottoming resistance.

I am not a math wizard and would like the help here from those who are. I dont know that I have the formulea written correctly but will give enough examples that the math wizards can correct the way that I wrote it.

(ATP / WB x RW x .5 + FTW) x ((EFH - BFH) / (FESL - FCSL)) x .43 = DCFSR (desired calculated front spring rate)

(18 / 49 x 180 x .5 + 99) = 132.06

((12 - 2.5) / (16.375 - 11.625)) = 2

132.06 x 2 x .43 = 113.57

DCFSR - 113.57

[forum]

whats your take on houser's long travel a arms. I just ordered some. I was gonna get the rp's but they delayed there release. so i said screw it.

[frozenh2o]

Nice thread Predator36...Question on your formula for front spring rate: It appears you are calculating a spring with 2.3 inches of sag, (rider on board) is that the purpose of the .43 in the formula?

[Predator36]

The best suspensions on modern dirt bikes are within several points of .43. That is an average number for a base line only. On XC for an older rider that does not have good endurance I have run as low as .37. I have seen aggressive (hard cornering) XC riders that prefere up to .45. Once I correct for excess sag the number will be a lot larger than that. You could also alter this number to calculate the spring rate for excess sag but I find it simpler to alter spring rate in percentage numbers. Many suspension guru's such as Paul Thede will end up in that range when setting up a bike or quad even if they dont do so by design but from rider and on board data info. Also remember that calculated spring rate numbers and a manufacturers spring rate numbers are differant.

[Predator36]

Originally posted by Predator36

WB - 49
ATP - 18
RW - 180
FESL - 16 3/8
RESL - 15 1/2
FCSL - 11 5/8
RCSL - 10 3/4
CRESL - 15 5/8
CRCSL - 11 1/4
FTW - 99
RTW - 104
BFH - 2 1/2
EFH - 12

Rear spring rate formulea:

((WB - ATP) / WB x RW + (RTW x 2)) X ((EFH - BFH) / (RESL - RCSL)) x .43 = DCRSR (desired calculated rear spring rate)

((31) / 49 x 180 + (208)) x ((9.5) / (4.75)) x .43 = 276.8

DCRSR = 276

[Predator36]

Every shock company and some spring companies in this industry have their own method/ terminology for identifying spring rates. One spring company will measure there spring at 1 inch compressed, one company will measure it at a percentage of its length, another company will measure a spring at a percentage of its travel, yet another company will provide a graph of the spring under actual load testing thru its entire travel. For the purpose of this setup we need something that will be a tad more universal. The best is if you have your own spring tester but since many dont, the web site listed below provides a very universal way to determine what we need. Be aware that differant spring materials can produce differant spring rates however most springs that you and I see are made from a high quality silicone based spring wire like is used by Eibach. I am not a spring wire expert but this is the best info that the spring companies have given me. I have my own home built spring tester and find that most of them are within an acceptable range. I have seen many springs once they are older maintain a close spring rate to when they were new but may measure a shorter free length. Anyone who can provide more info on this while still keeping it simple and user freindly, please do so.

http://www.proshocks.com/calcs/coilsprate.html

The numbers that you get out of this is what I refere to as "calulated" spring rates.

If you run a stock 400EX thru the previous measurements and then check the stock springs you will find that the front springs measure a tad stiff and the rear a tad soft.

Stock front
.323 wire
2.606 O.D.
11 coils

Stock rear
.431 wire
3.061 O.D.
10 coils

You ask how can the stock springs match my formulea so closely and the stock shocks not be as good as after market?? How can a stock YZ250F be just as close to this formulea on spring rates and still work so well?? There is a lot more to it yet.

[Predator36]

Using the measurments and formulea up to here would give you a race sag (rider standing on the pegs) of close to 25% of your travel. If your total travel is 9.5 inches you will end up with your frame around 9.6 inches off the ground with the rider standing on the pegs. If the shocks are valved properly for this setup and your application, you quad will work great for straight line racing/riding and jumping.

If this is the setup you are running adjust your race sag to around 9.6 inches frame to ground clearance in the front and the same or up to 1/4 inch lower in the back.

[Predator36]

Many riders today prefer their quad a lot lower to lower their center of gravity for greatly improved cornering and steep down hill rough sections. The first company that I saw address this issue was PEP with their ZPS setup. Several companies have tried to improve on this concept and have been more or less succesfull. I simply call this excess sag. When lowering your quad with excess sag, you will find that it bottoms out easily if no other adjustment is made. Several companies have played with a smaller spring on top that collapses when the rider is on the bike to get the sag that they wanted.They then ran stiffer compression valving to limit bottoming. That will work fine on landing from big jumps but will not give you the bottoming resistance that is needed in G out conditions. To make this concept work to its best everything needs to work together - same or slightly stiffer compression valving (I will address later - much later), stiffer main spring, soft sag spring, stiffer rebound to work with the stiffer main spring, and most important of all is that the front and back shocks work together when making these changes. First I will address the springs.

To find the main spring calculated rate for a frame race sagged to 8 inches you can start with the following formulea

EFH - 8 (sagged height) / (EFH - BFH) - .25 x 2 + 1 x DCRSR (or DCFSR)

This would result in a rear main spring for the 400ex that was measured be a calculated rate of 369.84 lbs.

The above is not a suggestion as I dont know what your riding conditions consist of. I have run a sagged height as low as 5.5 inches for MX and and have run as low as 3 inches for TT and have seen XC as low as 7 inches. I consider these numbers to be too low and prefer a starting point of 7.5 inches for MX, 8 inches for XC and 4.75 inches for TT but remember these measurements will only work with the correct shock and spring setup.

Originally posted by Predator36
That will work fine on landing from big jumps but will not give you the bottoming resistance that is needed in G out conditions.

sorry if this is a dumb question but whats a g-out?

[Predator36]

G out is when the weight of you and your bike compress the springs slow enough that shock valving has little effect. Most common place for this to happen is in the dunes when going thru the bottom of a bowl or going into the face of a large jump at high speed.

ok thanks:D

[Predator36]

Assuming I now have the correct main springs on my quad for the application I next need to choose the correct sag spring. Lets not argue about who's shocks and sag spring setup are the best as all the shock companies build great shocks except one (they fall apart and are worse than stock). I dont care if they are PEP, Axis, Elka, Afco, TCS, or Works, if they are setup for your needs they will work great. The best sag spring setup is a spring that will support the weight of the quad but will colapse when the rider stands on the pegs. Due to the front tires pushing out when the front of the bike goes down it is best to have the rider stand on the pegs and then roll the quad forward and back till the shocks settle in. If you are a math wizard you can use calculated spring rates to determine what size that spring needs to be. I have found what springs work best for this and can give the exact dimensions if someone wants to know.

Many times a shock that is not setup the best is viewed as great simply because it is the best that someone has ridden. Once I know a riding area or track, I make adjustments to the shocks just for that track.

Now it is time to set the ride height on the bike. Always set the ride height with the rider standing on the pegs. The only exception to this is PEP since it uses a very light sag spring. With the rider standing on the pegs - measure from the frame to the ground at the peg area and again at the front just before it turns up. The front and rear should be level or the rear lower to a max of 1/4 inch.

What the ride height should be is determined by the type of riding you plan to do and the sping setup that you have.

If you have questions on anything up to this point or want more help deciding how to adjust your bike, feel free to ask on this thread. I will help the best I can with the info that you provide.

What we have looked at so far is basicly checking the geometry of the chassis, changing it to our advantage, setting shock travel to match the chassis, and spring selection. Next thing I will address is shock valving (dont do this at home) Some of these things are adjustable at home but many of you are at the mercy of available parts. Some parts available are junk but mostly its a case of good parts that dont work together untill you or the manufacturer sets them up for you.

[Predator36]

Past experiance has shown that the closer that you get the rear main springs to match the previous formulea the better that they work.

The front springs I have gone a little softer a few times than the formulea but find that rider who rides a lot, has high endurance in his arms, is an aggresive rider, and does not jump correctly (cases jumps, lands nose high, lands sideways and etc.) prefers much stiffer front main springs.

[Claas900]

..Hello, I have a question ? and I'm sorry if its been answerd already, I may have over looked it, sorry. But how do you adjust the rear ride height on a no link?? And I know most ATV's dont have same travel front to rear,but like on a Cannondal, I dont know of a Long Travel rear, but they for offer a LT for the front, whats the advantage of the long travel on the front and no rear???..Thanks and Good job Predator36 were all learning a lot with this..

[Predator36]

Originally posted by Claas900
[B. But how do you adjust the rear ride height on a no link?? [/B]

If you look earlier on this thread you can see that I used an adjustable rear link to move the shock extended and compressed lengths to the proper locations. To adjust the compressed and extended travel on a no link you need to make changes to the shock. I did this on a freinds bike recantly. I measured his quad the same as with a linkage setup. His shock was to short, both extended and compressed. I installed a longer body on his shock to move the travel to where I wanted it.

To set the ride height correctly after this was done, I used the fomulea mentioned earlier and installed a stiffer main spring, then lowered the bike to the desired ride height with a sag spring on top.

[Predator36]

Originally posted by Claas900
[, whats the advantage of the long travel on the front and no rear???..[/B]

First we need to define - what is " Long Travel" This is one of the most abused terms in this industry. I have seen so called long travel a-arms that only had 9 inches of usable travel due to fact that the ball joint housing was welded in at a poor angle. There are several things that effect the length of your travel. How far the ball joints will move , how far the tie rod ends will move, how far your shocks travel, and how much travel you can have till the tie rods hit the frame when turning. The only true long travel front end that I have seen is the Leager T pin front end with a narrow frame. Does this mean that we all need Leager T pin front ends - No. There are several companies that have the correct geometry to place the travel so as to achieve sufficiant usable travel. I realise these comments may step on a few toes.

Another misconception is so called long travel shocks. There are shocks that are longer than others because of where the a-arm builder decided to place his shock mounts. Some shock companies prefere the longer shocks due to what it lets them do with the spring setup. It does not matter if your shock is 16 inches long or 19 inches long, if your usable travel is 10.5 inches, your front end will work very well. A longer shock does not mean it is longer travel. Measure the length of the exposed shaft for a little clue on this.

Back to your question - if you have longer travel in the front then the rear (and it is setup correctly) the front will feel plush and the rear will feel like junk, and you will quickly be on a mission to improve the rear.

Beware of so called Long travel products.

OK I'll get back off my stool now - I just had to vent on this issue.

if you have longer travel in the front then the rear (and it is setup correctly) the front will feel plush and the rear will feel like junk, and you will quickly be on a mission to improve the rear.

So have you been looking over my shoulder or something :D

I had been following this thread but had stayed away recently because I have been way too busy to tear this thing down and take the measurements etc. but since you just described my current front to rear problem perfectly I thought I would chime in.

Though I have not set up anything more than the ride height and external clicker positions the set up I have (houser lt w/elka 19" front and elka rear) no matter what I seem to do the front allways seems plush to soft, and the rear harsh to hard.

My point is that even with the ride height adjusted the ride is not where I can say it is right and the info you are posting here seems like it is the answer to the problem.

If the problem does end up being what I anticipate (rear shock travel/actual wheel travel and spring rates being so diff from the fronts) would you give any merit or thought to the moving of the rear shock top mount and the longer rear shock that some of the other members have gone to? Have any experience or thoughts on this?

And thanks this is a great thread :)

[Predator36]

Originally posted by 440EX4me

If the problem does end up being what I anticipate (rear shock travel/actual wheel travel and spring rates being so diff from the fronts) would you give any merit or thought to the moving of the rear shock top mount and the longer rear shock that some of the other members have gone to? Have any experience or thoughts on this?

And thanks this is a great thread :)

Yes this thought bears a lot of merit. I have no experiance with the change you mention but have heard a lot about it. If it adds usable travel (up to a reasonable limit) it would be a great improvment. I will look into this on my bike the next time I tear it down for major work.

[Dave400ex]

So your saying I could get a standard 16" a-arm and shock setup and if it was setup perfect I wouldn't notice much of a difference if I had the same a-arm/shock setup in the 19" that wasn't setup good?

[Predator36]

Originally posted by WarriorMan
So your saying I could get a standard 16" a-arm and shock setup and if it was setup perfect I wouldn't notice much of a difference if I had the same a-arm/shock setup in the 19" that wasn't setup good?

Thats correct.

[Merriman]

All this suspension talk is confussing me. I think it will be easier if I just bring my bike and all the suspension parts to your house in Ohio.

[Dave400ex]

So do you think it would be worth it to buy some Arens +1 16" a-arms for racing XC?

[Predator36]

Originally posted by WarriorMan
So do you think it would be worth it to buy some Arens +1 16" a-arms for racing XC?

I dont know since I never measured his a-arms but am confident that he can build a great a-arm. If someone has them and is willing to take his shocks off and get us 2 measurements I would gladly give you a better answer. Even better would be if Mr. Arens himself would help us out on this one.

[Dave400ex]

Well I don't believe John is in right now. I think Guy said he was going to be out of town. I'm not sure, but he is making some new LT arms for the 19" shocks, but I don't remember if he planned on making a set for just standard 16" shocks or not. If he did and I could get a chassis/suspension gain out of getting them then I would. I don't think I need 19" really, but want to get some a-arms like the 16" Houser's that have the special ball joints, heim joints, or whatever that help. Then all I would need is some 4+1 offset wheels and I would have a nice front end......

[dhines]

Bump - This thread is simply too good to fall very far down on the list!

And we seem to be missing a few lessons, no posts in a couple days :(

[Predator36]

When it comes to shock valving - the best education you can get is Paul Thede's video that comes with his gold valve kit. It will not tell you how to valve your shocks but will help you better understand how a shock works. I will only address how a shock works enough to get thru the down and dirty of hands on trial and error shock valving. Please do not do any of this at home unless you have the supervision of an experianced shock tech to help you.

First issue to address is the rebound. On many automotive shocks and a few other applications it is assumed that the spring is the main support and all that is needed to keep from bottoming. The shock is only used to limit the rebound velocity to keep you from bouncing up to fast. On performance shocks we ask a lot more of the shock, but the rebound is still one of the most critical issues.

The rebound valving on a shock needs to be matched to the spring that it is resisting. It is very simple if you have a rebound that is working perfectly to make a change to the rebound for a stiffer spring. If your shock has adjustable rebound on the rear, push down on the rear as far as you can then jerk up very fast and watch the rear tires drop. Do this several times and watch the rebound work. You can now adjust the rebound softer or stiffer and do this again to see the differance. Before you do this be sure that you know where your original setting was so you can set it back there before you ride again.

When going over rough terain the springs will lift your bike back up from the bottomed out position and push your wheels away when your bike leaves the ground. The rebound valving limits how fast this happens. If your rebound is too stiff your wheels will not drop away fast enough when leaving the ground and you will land with only part of your available suspension. In the case of a set of whoops - the impact from each bump will push the wheels further up since it did not rebound far enough before you hit the next one and after 3 or 4 bumps your bike will bottom out on a very small bump. This is called "packing up". This same rebound setting that is to stiff may work great on a large jump since the springs and gravity have more time to push the suspension to its fully extended position. If your rebound is to soft you bike will bounce back up too fast giving that end of the bike more lift over a jump and may bounce all over the place in a whoop section.

Internally the earlier shocks simply used an orfice to controll the amount of fluid passing thru a piston to controll rebound. This method is still used by several companies and is very easy to make internal adjustments for softer and stiffer needs. You can simply increase the orfice area by an equal percentage as the increase in spring rate if you install a stiffer spring and vice versa. Even though this may not be the best method, you will find it on some of the best shocks out there (and it works great) and will see more consistant results when changing springs, adjusting for differant bikes and riders, and adjusting for a host of other things. It is a very precise way to controll rebound as long as the same oil is used in the shocks.

Oil brand and weight is a very critical issue.

Any questions on rebound - feel free to ask before I discuss rebound shim valving.

[dhines]

Hey Pred,

Is the rebound orifice you are talking about the component of our shocks that we adjust when we change our rebound settings (assuming our shocks have adjustable rebound) or is a separate component.

Also, does the rebound have any impact on the compression of a shock - in other words if I increase my rebound will I notice a difference in the shock performance as it compresses or is it entirely isolated to the expansion movement?

One more question :p - how, if at all, does rebound affect performance while cornering, accelerating, etc.

Thanks,

Dennis

[Predator36]

Originally posted by dhines
Hey Pred,

Is the rebound orifice you are talking about the component of our shocks that we adjust when we change our rebound settings (assuming our shocks have adjustable rebound) or is a separate component.


Dennis

No, this oriface is in the piston. The external rebound adjustment is normally done by using a hollow shaft with a metering rod in the center to meter the amount of oil that bypasses the rebound valving in the piston.

[Predator36]

Originally posted by dhines
Hey Pred,



Also, does the rebound have any impact on the compression of a shock - in other words if I increase my rebound will I notice a difference in the shock performance as it compresses or is it entirely isolated to the expansion movement?


Dennis

On most shocks that are used on atvs the same hollow shaft/metering rod combination that allows oil to bypass the piston, the oil can bypass both ways. On those shocks the rebound adjustment will also effect compression but on a much smaller percentage. On a few shocks there is a check valve inside the shaft to limit the flow to rebound only.

[Predator36]

Originally posted by dhines
Hey Pred,


One more question :p - how, if at all, does rebound affect performance while cornering, accelerating, etc.

Thanks,

Dennis

On cornering, the rebound does have an effect but not nearly as much as proper quad setup, and a correct spring setup for you application.

Acceleration - rebound has a big effect as it effects weight transfer (how fast the front moves up) and how the drive wheels track the ground. Rebound that is to stiff will not let the wheels drop fast enough to track rough terain. Drag racers will use some wierd rebound settings for this reason.

[Predator36]

A better setup (but harder to fine tune for big changes) is shim valving for rebound. Works has a good idea here since they use a combination of an orfice and shims but let the oriface do most of the work. With shim valving the shock rebounds faster from the bottomed out position but as it comes up and slowes down, the shims start to close and slow down the rebound. This lets you have faster rebound at the bottom of the stroke (where the spring is the stiffest) and yet slower rebound toward the top of the stroke vs. a simple oriface. This helps to track the ground better on acceleration and provides a smoother action. However this setup is not as precise when making changes which makes for more trial and error testing.

Some shocks like the 400ex rear shock have a broad enough range of external rebound adjustment that internal changes are less critical. On the 400ex shock the external rebound adjustment is simply a bypass around the piston and the external rebound adjustment will effect both rebound and compression.

Many shocks (including the 400ex rear shock) use multi stage rebound shims.

The main differance between the oriface only valving and the shim valving is that the shim valving is velocity sensetive. This is not a big thing if the shock is setup correctly but there is a differance.

[MillerTime]

I'm a little late on this post, but wondering if you could help me out or clearify something for me.
In the begining stagest of setting up the front suspension, at 12"
my tie-rods hit the upper a-arms. does that mean that I have to drop my overall frame hight from the standard 12".

and also how are you measuring the difference in the front and back suspension, you said that your front is at 16.5 and you needed your rear at 15.5, How did you figure out that you .25 off.
any info. that you could give me would be appreciated.

[Predator36]

Originally posted by MillerTime
I'm a little late on this post, but wondering if you could help me out or clearify something for me.
In the begining stagest of setting up the front suspension, at 12"
my tie-rods hit the upper a-arms. does that mean that I have to drop my overall frame hight from the standard 12".

.

The answer is yes.

When you set your frame at 12 inches , you found a limiting factor that will not allow you to go this far. Your extended shock length must be short enough to avoid part contact that could potentialy break parts. Or a part combination that will work without makeing contact at your desired extended length.

[Predator36]

Originally posted by MillerTime
and also how are you measuring the difference in the front and back suspension, you said that your front is at 16.5 and you needed your rear at 15.5, How did you figure out that you .25 off.
any info. that you could give me would be appreciated.

I may have made this a little confusing.

On my bike setup I adjusted front shock extended and compressed length to match the bike.
On the rear I chose to adjust the bike to match a given shock extended and compressed length. In this case if you go back and read my measurements you will see that I cant get the compressed and extended length that I would like to have.

[Predator36]

Sorry for the long delay. I have been very busy and will be out of town for the next week. I want to address compression valving next and hope to get some graphs to go with it from Paul Thede. He may not be into quads but he understands suspension better than anyone I know.

[dhines]

Back on top...

[nacs400ex]

What happened to this thread???

What happened to this thread???

Thats what I have been thinking :confused:

Maybe the predator became the prey :eek: :D

Too bad though cause this was a great thread.

[remlapr]

He still post here occasionally - at least I remember seeing some a couple of months ago. I think he owns or works at a shop....

On the 400ex shock the external rebound adjustment is simply a bypass around the piston and the external rebound adjustment will effect both rebound and compression.

Anyone know if this is this true on rear shocks other than stk? Like elka, pep or axis?

[Evan]

Originally posted by Predator36
On cornering, the rebound does have an effect but not nearly as much as proper quad setup, and a correct spring setup for you application.

Acceleration - rebound has a big effect as it effects weight transfer (how fast the front moves up) and how the drive wheels track the ground. Rebound that is to stiff will not let the wheels drop fast enough to track rough terain. Drag racers will use some wierd rebound settings for this reason.



Im curious as to the best way to set up for acceleration. I race MX, but it seems that there is a better way to setup suspension for holeshots. I know in dragracing as u said, susp. is a big part, all the power in the world is nothing if u cant get it to the ground. My biggest problem I belive on my R is to long of swingarm(stock 86) but Im wondering if I can adjust my suspension to help (ie rebound as u were sayin) Thanks

[toomeyshee87]

anyone know why my pep zps shocks are for stock shock mounts and stock shocks are 16" but wayne built my shocks 14.75"?

[QuadTrix6]

Originally posted by toomeyshee87
anyone know why my pep zps shocks are for stock shock mounts and stock shocks are 16" but wayne built my shocks 14.75"?

where are u measuring from? You should be measuring from eyelet to eyelet in the center of each. If you said for a 400ex and standard travel they should be 16 1/4.

[toomeyshee87]

its for a banshee

[QuadTrix6]

i dont think stock banshee shocks are 16 inches :confused: i think they are 14.75.

[toomeyshee87]

o, my bad:uhoh: