how do I measure shock sag?

[cbr929rr]

I will be setting up my suspension once my revalves are shipped and I do not know how to set the sag on the rear shock lower than the front.
I have used the search button
I have read to measure at the pegs but this does not seperate front and rear sag
If you measure off the rear grab bar and another point on the front bumper where are your starting points (i'm confused)
thanks for any help

[400exrider707]

Put it on flat level ground.. The rider must be on the bike at the time of measurements!!! Measure from the bottom of the frame right underneath the pegs to the ground. Next measure the from the bottom of the frame up front (go forward up the frame from the pegs to the point where it starts to rake. Measure from that point to the ground. Your peg measurement should be 1/4 to 1/2 in lower with the rider on it.

[bwamos]

What he said.

I actually like mine about a 1/4" nose high so it doesn't dive in the corners.

[bradley300]

i think you guys are talking about ride height, and i think he needs to know his rear sag. for that, do this

put your quad on level ground.

mark a spot somewhere on the sub frame. i used a grab bar mounting bolt, just makes things easy.

have a freind pull up on the rear of the quad, to just where the tires are about to come off the ground if it ws lifted any higher

while your friend holds the quad, measure from the ground to the spot you marked on your subframe. call this measurement 1.

now sit on the quad, jump up and down a time or two to get the suspesnion in a nuetral position.

now sit in your riding position with all your gear on.

while you are sitting down on the quad, have your freind measure from the ground to your mark on the subframe. call this measurement 2.

take measurement 1, subtract measurement 2 and that is your rear sag.

repeat until you have the corect sag.

once you have the correct sag, measure the rideheight in the rear from the ground to the bottom of the frame under the foot peg. this is your rear ride height

measure from the ground to the bottom of the frame 22 inches foward of the rear ride ehight measurement (should be right around a a-arm mount)

now whatever the rear ride ehight was, adjust the front so that it sits .25 to .5 inches higher than the rear if you have a honda, .75 higher than the rear if you have a yamaha. do all ride ehight adjusting with you on the quad with your gear on

[cbr929rr]

I think i understand now thanks for your help.

[400exMO]

bradley300 what's the purpose of setting the rear sag?? What do you want your sag to be?

[bradley300]

WARNING, long post, i rambled on a bit, and there is lots of mispelled words and long sentences. it early. i'll edit later.
abbreviated version- its all about varying tire sizes vs. correct up and down travel of the shock

i try to listen to laz at gt thunder when he talks and read what he types, and here is what i have gathered:

Its just alot easier to dial in rear sag than it is to dial in rear ride hieght. By dialing in the rear ride hight, you are really finding the correct shaft position with the rider on board. This gives the rear shock the correct amount of up and down travel from the nuetral position. The problem with trying to do this with ride height is rear tire size. Even within the same size tire, different brands have different sizes (ive seen labled 20 inch tires that actually measure from 18.5 inches to 21 inches depending on the brand and model of tire). So instead of valving for a specific ride height, its easier to just valve for the correct amount of sag and let the ride hieght be what it is.

For example, you and I have the same set up. Same quad, linkage, a-arms, swingarm, shocks, shock builder, weight etc... but i have 20 inch holeshot xcr's ( actually19.5 inches tall) and tireballs (makes the quad sit lower) and you have 20 inch razr 2's (actually about 21 inches tall).

The shock builder has built both shocks for a 20 inch tire, and we try to tune the rear by adjusting and measuring ride hieght. We CAN both can get the ride height we want, BUT- sinch your tires are taller than what the shock is built for, you will have to take out more pre load (adding more sag) to get the same ride hieght. I would have to add more preload (less sag) to get the same ride hieght as you. Now we both have the correct ride height that our shock was built for.

The issue is now, our shocks were made for exactly a 20 inch tire. Since your tire is taller than that you have compensated by taking out more preload (and adding sag). Now your shock is not in the best neutral position for adequate up and down travel. Your shock is now too short, so it will bottom easier. My shock is too long, making it stiff.

So in the end, if we would have both just measured by rear sag both shocks would have been in the perfect neutral position, but my quad would sit a hair lower than yours.

Since the rear sag is correct, we can now measure what the ride rear hieght is. We are'nt changing anything on the rear now, just measuring for information purposes. Since now we know the rear ride height, we can adjust the front ride height to whatever is needed. (.25-.5 inches higher front than rear on a honda, .75 inches higher front than rear on a yamaha). This helps with weight bias, which helps steering. You will notice yamaha's have a greater back/front combo than a honda, this is to make up for the lack of rake on the yamaha front end.

Now, since my ride hieght is lower and we have the same quad, my front shocks will also be a hair lower since we would run the same front/rear bias. Because of this, my shocks could be a little softer, but i can play with the adjustments to get them really close. It is better for the fronts to be "close" than the rear since the rear works so hard. but since the rear is right, i can valve my front shocks around my rear shock.

Most people wouldnt notice these small differences but they can really make a difference. It really shows how everything you do affects something else.

In a perfect world, you would give the shock builder the extended and compressed lengths of front and rear shocks, and measure exact tire height of all the tires. As well as all other normal set up measurements like swingarm/a-arms length, linkage.... to give you a perfect perfect set up front and rear. Make sense?

do these with all 3 shocks off the quad.
extended length: set your quad on 12 inch blocks, measure from eye to eye on the shock mounts.

compressed legth: but a 2X4 flat on the ground longways and set your quad on top of it. measure eye to eye on both shocks again

as for what should your rear sag be, i could be wrong, but i am almost positive it needs to be about 30% of the travel. this is with the rider

[400exMO]

thanks. What do you want your rear sag to be set at?

[bradley300]

i must have still been editing when you posted. you want the rear sag to be about 30% of travel with you on the quad.

[400exMO]

alright thanks, sorry for all the questions, I'm finding this very imformative. It's something I've never considered checking.

When you are talking about checking extended and compressed length you set the FRAME of the quad on twelve inch blocks and the 2x4? Would what type of shock and aarm manufacturer change the heights you measure both of those at? like needing the quad 13 inches in the air instead of 12?

[bradley300]

yes, but the frame on the blocks

i asked laz about your question (i wa a little confused myself. with that method it would seem every quad would only have 10.5 inches of travel) this is cut and paste from one of our PM's on another site

The 1.5 and 12 inch measurement does not in anyway represent compressed or extended shock length - it simple is the foundation measuremts from which I design shocks and calculate leverage ratios for differant applications.

he also said that 30% sag works wel on a bike, but not a quad. i couldnt get a straight answer about what percentage works best on a quad, but he said i need between 4 and 5 inches of sag. knowing that i can start at 4 and go up and down to find where it feels best.

[esr250r86]

Originally posted by 400exrider707
Put it on flat level ground.. The rider must be on the bike at the time of measurements!!! Measure from the bottom of the frame right underneath the pegs to the ground. Next measure the from the bottom of the frame up front (go forward up the frame from the pegs to the point where it starts to rake. Measure from that point to the ground. Your peg measurement should be 1/4 to 1/2 in lower with the rider on it. thats sort of what I do with mine.

[400exMO]

Originally posted by bradley300
yes, but the frame on the blocks

i asked laz about your question (i wa a little confused myself. with that method it would seem every quad would only have 10.5 inches of travel) this is cut and paste from one of our PM's on another site

The 1.5 and 12 inch measurement does not in anyway represent compressed or extended shock length - it simple is the foundation measuremts from which I design shocks and calculate leverage ratios for differant applications.

he also said that 30% sag works wel on a bike, but not a quad. i couldnt get a straight answer about what percentage works best on a quad, but he said i need between 4 and 5 inches of sag. knowing that i can start at 4 and go up and down to find where it feels best.
thanks for all your help, I know what I'll be doing tonight!:devil:

[bradley300]

no problem!