Fork fluid amount?

[turbocamino]

Gentlemen, My new race-tech 1.0 springs are going in tomorrow ,on my 89,and am not 100% sure on the fluid amount....search suggests anywhere from 125 to 150mm from top of fork tube...what does that range reflect?   ie;stiffer,less rebound,etc.....i have 10wt fluid and i weigh in at 175lbs. and my rides lean toward the sportier side. thanks very much.

[Arnie]

The trapped air acts as a progressive spring as you approach fork bottoming.
The oil height affects the increased spring rate as the fork compresses.  Higher oil will give more rapid spring rate increase and prevent bottoming.  Lower oil height will continue to provide a single rate longer as the fork compresses.
What this means for you is that the fork will feel stiffer with more oil on BIG bumps.
On normal smooth(ish) roads it won't be noticable.

Choose a starting point and try it for a month.  Then either add or remove some oil and feel the difference.  Its easy enough to try it and see.

Cheers,
Arnie

[FJ Flyer]

Good starting point is, with springs out, compress the fork, and fill 130-140 mm from the top.

[turbocamino]

Ok ,i understand,thanks.    To bad for me i had never done any fork work previously....i pulled the caps off the forks with bike on kick stand only...wont do that again! 

[Pat Conlon]

Thanks for sharing that....LOL, I don't feel so bad now....

That reminds me, we should start a thread of the stupidest things we have done in working on our FJ's....
I got a couple of zingers.

and I bet a jelly donut that I'm not alone....

Ok ,i understand,thanks.    To bad for me i had never done any fork work previously....i pulled the caps off the forks with bike on kick stand only...wont do that again! 

[tqmx1]

Pat, Are you or I going to start that topic in the general discussion {I also have a few good ones) 

[Mark Olson]

go ahead and kick it off I'll play.

Pat, Are you or I going to start that topic in the general discussion {I also have a few good ones) 

[andyb]

Pretty much true.  The air gap acts like an additional spring in a way.  A smaller air gap (more oil) makes the forks less linear when they get near the limit, and helps resist bottoming.  A bigger air gap lets them stay linear longer through their travel.

You can also play with spacers to change the preload on the forks, and play with fork oil types to change the amount of damping through the range.  I'm too lazy to link it, but there's a bigass pile of information about suspension setup elsewhere in the forums.

The trapped air acts as a progressive spring as you approach fork bottoming.
The oil height affects the increased spring rate as the fork compresses.  Higher oil will give more rapid spring rate increase and prevent bottoming.  Lower oil height will continue to provide a single rate longer as the fork compresses.
What this means for you is that the fork will feel stiffer with more oil on BIG bumps.
On normal smooth(ish) roads it won't be noticable.

Choose a starting point and try it for a month.  Then either add or remove some oil and feel the difference.  Its easy enough to try it and see.

Cheers,
Arnie