Explain shock pre load?

[nakomis0]

What benefits or charastics does pre loading a rear shock do?

I understand pre load.. as compressing the spring..

But I dont know why you would do this... all i can think of is that it makes for a stiffer ride..... and i think it would lower your ride hight.

So could ya clue me in a little more on what pre loading a shock is for?

preload is the tension on the spring. When you screw the nut down it raises ride height and when you raise the nut up on the shock body it lowers ride height. :)

how does preload not effect bottoming??? if the spring is stiffer it will make the shock harder to compress and vice versa? please explain this :confused:

[nakomis0]

Originally posted by 93 300ex
how does preload not effect bottoming??? if the spring is stiffer it will make the shock harder to compress and vice versa? please explain this :confused:

I guess it doesnt effect bottoming out because.. its still gonna take the same amount of force to bottom out the shock.

The compression is still gonna be the same.

It seems like it would bottom out a little more just because it is preloaded and the inch or whatever it is lower could of took some impact of the force .. i dont know whatever :confused: but...

.... So Pre load is just for adjusting ride height?

Preload is just a way to put a constant amount of pressure on the spring and this affects the quad in a few ways.

If the preload is increased it will stiffen the spring in the initial compression due to the added load on the spring. It will also RAISE the ride height by requireing more weight to compress the spring etc.

If the pre load is decreased it will soften the sprig in the initial shock travel due to the lowered load on the spring. It will lower ride height also.

There is a excelent shock/suspension thread thats active now so search it down.

[stupid driver]

the reason it dont effect it is this: When you loosen it, the shock is softer, but it is also raised up a little. when it is tightened, the shock is stiffer, yet it is shorter. These 2 characteristics ballance out, and that is why it dont effect bottoming out

Originally posted by stupid driver
the reason it dont effect it is this: When you loosen it, the shock is softer, but it is also raised up a little. when it is tightened, the shock is stiffer, yet it is shorter. These 2 characteristics ballance out, and that is why it dont effect bottoming out

Simplified version is the spring in the shock has a certain poundage per inch that is need to compress it and putting extra tension on the spring doesnt change this at all.

The springs motion at the top of the stroke will be harsher since the it will be pre loaded where b4 it wasnt.

The valving has much to do with bottoming resistance also.

[Dirt]

Preload does effect bottoming. Springs offer force per distance compressed/extended. When you preload a shock you are changing the length of the spring at both ends of the shocks travel. You are not changing the travel of the shock. For example you crank your preload collars on your stock 400ex rear 1inch down you just increased the distance the spring is compressed from its relaxed position 1inch. So if the 400ex stock rear spring has a rate of 420lbs/inch then you just added 420lbs at both ends of travel, meaning you must exert another 420lbs to bottom the shock and to get it to have the same ride hight as before the adjustment.

Don't confuse preload with ride height adjustment. But preload does effect ride height. Confused? :D

Originally posted by Dirt
Preload does effect bottoming. Springs offer force per distance compressed/extended. When you preload a shock you are changing the length of the spring at both ends of the shocks travel. You are not changing the travel of the shock. For example you crank your preload collars on your stock 400ex rear 1inch down you just increased the distance the spring is compressed from its relaxed position 1inch. So if the 400ex stock rear spring has a rate of 420lbs/inch then you just added 420lbs at both ends of travel, meaning you must exert another 420lbs to bottom the shock and to get it to have the same ride hight as before the adjustment.

Don't confuse preload with ride height adjustment. But preload does effect ride height. Confused? :D

I am confused by this :D

If a spring has a rate of X and you apply that pressure to it will it not compress it fully?

So if it takes 200lbs of force to compress a spring 2" with a 100lb per inch rating then how would it matter if the force comes from rider weight, preload or the force of that rider landing a jump.

Help us out here

[Dirt]

Ok, first of all we are talking about single spring shocks hear. Not ride height adjustable zero preload.

Ok, If you remove the spring off of the stock 400ex rear shock it will extend to its relaxed length say 12inches for example, lets call that length (0), and the spring rate is say 200lbs-inch = k. When the spring is put back on the shock( which is fully extended) it can have a length from 8 to 11 inches due to the fact that the top spring seat (Preload Collar) is adjustable up and down on the dampener body. That means that the spring is preloaded from 1 to 4 inches and exerting a force from 200 to 800lbs. If the shock assembly has a length of "travel" of 6 inches, when the shock is fully compressed the spring is compressed the amount of "travel" plus the initial preloaded length. So fully compressed the spring will exert a force from 1400 to 2000lbs (preload force + k * travel = force when fully compressed) or (200+200*6=1400 to 800+200*6=2000).

Meaning that by adjusting the preload collar you change the overall distance that the spring is compressed from its relaxed length called length 0. When compressed it exerts a force per unit of distance. So for every inch compressed it exerts another 200lbs. The travel is always the same but the distance the spring is compressed is adjustable... so at 1inch preload you get 200lbs (extended) to 1400lbs (compressed), and for 4inches of preload you get 800lbs (extended) to 2000lbs (compressed).

Hope this helps :D

[stupid driver]

Originally posted by Dirt
Ok, first of all we are talking about single spring shocks hear. Not ride height adjustable zero preload.

Ok, If you remove the spring off of the stock 400ex rear shock it will extend to its relaxed length say 12inches for example, lets call that length (0), and the spring rate is say 200lbs-inch = k. When the spring is put back on the shock( which is fully extended) it can have a length from 8 to 11 inches due to the fact that the top spring seat (Preload Collar) is adjustable up and down on the dampener body. That means that the spring is preloaded from 1 to 4 inches and exerting a force from 200 to 800lbs. If the shock assembly has a length of "travel" of 6 inches, when the shock is fully compressed the spring is compressed the amount of "travel" plus the initial preloaded length. So fully compressed the spring will exert a force from 1400 to 2000lbs (preload force + k * travel = force when fully compressed) or (200+200*6=1400 to 800+200*6=2000).

Meaning that by adjusting the preload collar you change the overall distance that the spring is compressed from its relaxed length called length 0. When compressed it exerts a force per unit of distance. So for every inch compressed it exerts another 200lbs. The travel is always the same but the distance the spring is compressed is adjustable... so at 1inch preload you get 200lbs (extended) to 1400lbs (compressed), and for 4inches of preload you get 800lbs (extended) to 2000lbs (compressed).

Hope this helps :D

let me know when you graduate from Yale. pretty technical stuff, lost me in the first sentence :p

[ralph2]

why do u want zero preload for mx conditions and preload for more woods racing,,, ?:rolleyes:

Originally posted by stupid driver
let me know when you graduate from Yale. pretty technical stuff, lost me in the first sentence :p

Dont give up, just take it apart one piece at a time and think about it till it makes some sense. its damn confusing for sure but worse if you try to aborb it all at once.

Originally posted by Dirt
Ok, first of all we are talking about single spring shocks hear. Not ride height adjustable zero preload.

Ok, If you remove the spring off of the stock 400ex rear shock it will extend to its relaxed length say 12inches for example, lets call that length (0), and the spring rate is say 200lbs-inch = k. When the spring is put back on the shock( which is fully extended) it can have a length from 8 to 11 inches due to the fact that the top spring seat (Preload Collar) is adjustable up and down on the dampener body. That means that the spring is preloaded from 1 to 4 inches and exerting a force from 200 to 800lbs. If the shock assembly has a length of "travel" of 6 inches, when the shock is fully compressed the spring is compressed the amount of "travel" plus the initial preloaded length. So fully compressed the spring will exert a force from 1400 to 2000lbs (preload force + k * travel = force when fully compressed) or (200+200*6=1400 to 800+200*6=2000).

Meaning that by adjusting the preload collar you change the overall distance that the spring is compressed from its relaxed length called length 0. When compressed it exerts a force per unit of distance. So for every inch compressed it exerts another 200lbs. The travel is always the same but the distance the spring is compressed is adjustable... so at 1inch preload you get 200lbs (extended) to 1400lbs (compressed), and for 4inches of preload you get 800lbs (extended) to 2000lbs (compressed).

Hope this helps :D

Thanx

Now i see the calculations but I am so thick skulled that I keep changing them in my head everytime I re read them. I just keep missing why the spring will exert more force as its compressed since I have been lead to believe that a single rate spring is linear.

Trust me I am not saying your incorrect just that I am confused with why there would be a difference if the spring was compressed initially by the preload of the shock or the result of a landing etc.


If you preload a spring (using your same specs 200lb in etc)

think about when u push a spring together it wants to return to its normal state so it puts a force against you. im not sure if i answered your question but it makes sence to me.

[Dirt]

Remember, the spring doesn't compress to its max when the shock bottoms, the shock (bumper on bottom of shaft hits the bottom of body) itself bottoms. Get it? The shock is designed to bottom before all the coils on the spring contact each other. That’s why the bumper is on the shaft. If it wasn't that way when you increased preload you would shorten the travel, and create some very harsh landings.

So again, by increasing the preload you increase the overall distance the spring is compressed from its relaxed length.

I hear what your saying and I guess I understand your point but what I dont get is how applying pressure to compress a single rate spring effects the amount of pressure to needed to compress it further.

In other words if it takes 200lb to compress the spring 1 inch then it should take 600lb to compress it 3 inches, now why would it matter to the springs rate if youv compressed it 1 inch first with 200lb of force from the pre load to make it need more than 400lb force to move it the other 2 inches?

[Dirt]

"In other words if it takes 200lb to compress the spring 1 inch then it should take 600lb to compress it 3 inches, now why would it matter to the springs rate if youv compressed it 1 inch first with 200lb of force from the pre load to make it need more than 400lb force to move it the other 2 inches?", 440EXme.

Ok, if you preloaded the spring 1 inch it would exert 200lbs but to move it the remaining 2 inches you would need to apply 600 lbs, because it wouldn't start to move untill you applied at least 200 lbs. (Newton)

Try this, you have two springs both 200 lbs/inch. One at relaxed length and the other preloaded 1 inch. Push both springs down 3 inches, the relaxed spring would exert 600lbs and the preloaded spring would exert 800lbs. Because the preloaded spring actually was compressed 4 inches from its relaxed length.:D

Ok I crammed that into my brain and it made sense but (damn theres allways a but LOL) isnt what your saying the same as what I am saying?

Maybe I should refrase it to "an additional 400lb of force".

So it is true that a spring with a certain rate will still need that amount of force to compress it a certain amount no matter if that force was preload or what ever.

And for those who arent into the tech side of this in my first hand exerience with the stock front shocks on the EX adding pre load made it ride more harsh over the small stuff but it still bottomed over the normal stuff it had with the softer settings.

So I guess it all makes sense after all :)

[Bad Habit]

I understand what you are saying (finally):)
If I may add something to try and clarify.
Don't get hung up with the length of spring (like I was). Try to think of it at starting points. Relaxed spring = 0lbs. 1" Preloaded spring = 200lbs. So to move either of these springs 1" you need to apply 200 lbs. of additional pressure.

Maybe another way......Think of 2 springs standing up on the floor. Put a 200lb weight on one and nothing on the other. Now you want to compress each spring 1". You have to put 200lbs on each spring to get them each to move the 1". They both traveled the same distance but the one spring has more tension on it.

Did I help or did I just confuse myself more?:D

Originally posted by Yellow416ex
I understand what you are saying (finally):)
If I may add something to try and clarify.
Don't get hung up with the length of spring (like I was). Try to think of it at starting points. Relaxed spring = 0lbs. 1" Preloaded spring = 200lbs. So to move either of these springs 1" you need to apply 200 lbs. of additional pressure.

Maybe another way......Think of 2 springs standing up on the floor. Put a 200lb weight on one and nothing on the other. Now you want to compress each spring 1". You have to put 200lbs on each spring to get them each to move the 1". They both traveled the same distance but the one spring has more tension on it.

Did I help or did I just confuse myself more?:D

LMAO I love your last statement, so strue :)

So do we all agree that it would take a total of 600lb force to compress a spring with a 200lb inch rating 3"? Or am I loosing it again :D

[Dirt]

Yes it would take 600lbs to compress a 200lb/inchs spring from relaxed (0) down 3 inches. But if you preload it one inch you need 800 lbs to move it 3 more inches. The preload adjustment is on the side of the shock body.

The reason you still bottom is that the springs are two soft and or they are not preloaded enough or the valving is too soft. If you could get stock shocks to ride smooth and not bottom, why would anyone need aftermarket? :D