fork oil?

What oil weight are you guys running in you forks?
Want to stiffen up my rebound a bit, any suggestions?

Since the 175's call for 10w oil, i ran a mix of 10 and 15w at a 3:1 ratio.

5weight or 5w20 synthetic... PJ told me this one... heavier fork oil doesnt increase dampening and running a heavier weight is really just a ghetto way of making up for worn springs. you want super light weight so that the oil can move freely. if you want MORE dampening, weld a couple of the holes shut in the dampening rod. want less, than drill the holes bigger.

Rocan said:

5weight or 5w20 synthetic... PJ told me this one... heavier fork oil doesnt increase dampening and running a heavier weight is really just a ghetto way of making up for worn springs. you want super light weight so that the oil can move freely. if you want MORE dampening, weld a couple of the holes shut in the dampening rod. want less, than drill the holes bigger.

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Thanks for the info man.

Rocan said:

5weight or 5w20 synthetic... PJ told me this one... heavier fork oil doesnt increase dampening and running a heavier weight is really just a ghetto way of making up for worn springs. you want super light weight so that the oil can move freely. if you want MORE dampening, weld a couple of the holes shut in the dampening rod. want less, than drill the holes bigger.

Click to expand...

I think you got that the wrong way round - changing the weight of your oil does affect your damping rates.

It won't stiffen up worn springs though.

I'm referrring to 'conventional' damper rod forks here
With stock springs (or worn springs) 20 wt oil is generally a bad idea although many here will recommend it
Thicker oil will increase compression and rebound damping.
Forks don't work properly if you hit a bump that accelerates slider on fork tube faster than oil can move through compression holes (fork 'locks up')
If you hit a series of undulations (small 'rounded bumps') with thick oil, the forks will 'pack down' which can upset handling pretty dramatically.
Under heavy braking, the forks hydraulic lock because oil can't move through the damper rod holes fast enough to allow suspension to work (which is why vintage racers like it, no front end 'dive')
Slightly thicker oil changes the range where forks operate correctly, it's going to make them work slower and lock up earlier if you hit a sharp edged bump.
Personally, I use 5w/20 full synthetic engine oil, it's smoother than 'ordinary' oil and doesn't thin out as suspension operated and gets hot.
The viscosity doesn't directly translate to ATF or fork oil but is probably similar to 7~10wt (it's thicker than 5wt fork oil)
Rocan is right saying to weld up damper rod holes, but, you have to drill new ones either same diameter in a different place (lower/higher on damper rod) or drill smaller holes.
The important thing is get spring rate right before you mess with damping

Word, thanks for all the help guys. Im no stranger to suspensions or how they work, but all the suspensions ive ever worked on have been with cars, race and street. Just wanted to see what everyone was rocking as far as oil weight and who like what and why. Also thanks for the info on engine oil in forks. Ive herd that in the past but not from someone who actually did it. Thanks again
-Max

I personally would resist using engine oil when you can get high quality synthetic suspension fluid. It is designed to resist fading as it heats up ( not as much an issue on forks as it is on shocks ), has foam inhibitors, additives to help keep your seals pliable and fight stiction.

I wouldn't use anything heavier than 15wt ( unless called for from the factory ). crazypj explained it well.

"The important thing is get spring rate right before you mess with damping" Great Advise.