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Discussion Starter · #1 ·
Hey everyone,

I am working on a project for my differential equations class in which we are trying to model the compression of a front fork vs. time as you land off a jump. I cannot find any information about the damping rates of a front fork anywhere, and I was hoping someone might have some information that might help me.

I'm sure companies dyno forks; does anyone have graphs or numbers they could send me? Doesn't really matter what fork; something in the 4-6" range with a linear coil spring would be ideal, but anything would help.

While I'm at it, anyone have any numbers for spring rates? Everything I've seen online is labeled as blue, yellow, or purple, and I'm just not sure what d/dt(purple) equals ;) I've got a fork I can pull apart and measure the spring rate directly, but if anyone knows offhand it'd save me some time. We tried measuring the spring rate with the fork assembled, but it's in terrible shape and has such bad stiction our numbers were all over the place.
 

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You may want to contact Fox, Rock Shocks etc, and see if they can give you some technical data that will help you out. You also may want to look on dirt bike forums, trophy truck sites, etc, since those work the same way.
 

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Discussion Starter · #5 ·
Thanks Rock Climber. Those numbers will save me some time for sure.

I tried emailing Push but didn't get a response. I'll give the suspension companies a try. If we can't come up with any data we'll go at it backwards and analyze what damping rate would be best for given conditions based on our equation. We have our equation written so that damping is directly proportional to the velocity at which the fork is compressing, which I suspect is not at all accurate in modern forks (especially considering that most forks have adjustable rebound and compression damping, whereas we are assuming compression damping is identical to rebound), but serves the purpose for our project. It would be nice to have some numbers so that we could see how close or far from the case that really is though.
 

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pressingonward said:
Thanks Rock Climber. Those numbers will save me some time for sure.

I tried emailing Push but didn't get a response. I'll give the suspension companies a try. If we can't come up with any data we'll go at it backwards and analyze what damping rate would be best for given conditions based on our equation. We have our equation written so that damping is directly proportional to the velocity at which the fork is compressing, which I suspect is not at all accurate in modern forks (especially considering that most forks have adjustable rebound and compression damping, whereas we are assuming compression damping is identical to rebound), but serves the purpose for our project. It would be nice to have some numbers so that we could see how close or far from the case that really is though.
This is not even close to correct and one reason why each rider could have their entirely own settings of the shim stacks. Shimmed valving is primarily speed sensitive, not position sensitive, or in any way directly proportional to velocity.

Compression and rebound should be no where near matching. As a general rule, and this varies widely, compression is 10% of rebound.

I have this program but have never used it, maybe the link will help you. I'd bet if you wanted you could buy Shimrestacker and do 100% of your project and even win the science fair.

http://www.shimrestackor.com/

PK
 

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PUSH's info is valuable intellectual property, so it's no surprise you didn't get an answer. It's like asking Coke for the formula for your chemistry class.
 
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