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  1. #1
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    Oil Weight - Fork Performance

    How does oil weight affect fork performance (rebound, compression)?
    5wt vs 10wt vs 15wt, etc...

    My fork recommends 15wt, but I plan on experimenting with a couple different weights.

  2. #2
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    The greater the weight (higher number) means the oil is thicker and will move through damping circuits etc slower going much higher than 15wt can be too thick.What fork are you talking about?
    Do people think you are strange??

    Do you??

    ....Then you may be on the right track.
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  3. #3
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    It's a 1998 SID w/ old 15wt oil. I was going to try 10wt and see what happens. Pretty much a fork to experiment with. Bad idea, good idea?

  4. #4
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    Quote Originally Posted by tojnom
    It's a 1998 SID w/ old 15wt oil. I was going to try 10wt and see what happens. Pretty much a fork to experiment with. Bad idea, good idea?
    Now there's a blast from my past. I had a 99 SID which was probably pretty similar to your 98. I seem to remember that both the air spring and dampening cartridges were sealed units in that fork so changing oil weight wouldn't really have any effect on the action of the fork with regards to dampening. No doubt fresh oil will give your fork a smoother action though and a lighter weight wouldn't hurt anything, it would probably splash around more and do a better job lubricating the bushings.

  5. #5
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    Both the air spring and dampening cartridges are sealed, so oil weight probably won't make much of a difference. Eventually I will have to do some maintenance on my other fork (Fox 32F-100RLC) and wanted some input on oil oil viscosity.

    You'll get a kick out of this...never taken the lower tubes off this fork in 10 years! Now I'd be lying if I told you I rode it every year, it sat for three years in the basement. But it has been ridden 3-4000 miles with little to no maintenance, just kept 60-80psi and lube.

    It's still in great shape, lightweight 2.5lbs, and a whopping 60mm of travel! Excellent fork for the winter months in Ohio...

  6. #6
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    Quote Originally Posted by tojnom
    Both the air spring and dampening cartridges are sealed, so oil weight probably won't make much of a difference. Eventually I will have to do some maintenance on my other fork (Fox 32F-100RLC) and wanted some input on oil oil viscosity.

    You'll get a kick out of this...never taken the lower tubes off this fork in 10 years! Now I'd be lying if I told you I rode it every year, it sat for three years in the basement. But it has been ridden 3-4000 miles with little to no maintenance, just kept 60-80psi and lube.

    It's still in great shape, lightweight 2.5lbs, and a whopping 60mm of travel! Excellent fork for the winter months in Ohio...
    I had a friend who didn't think it necessary to change fork oil. He said he never has to change his cars shock oil so why change the bike oil?? I finally convinced him to give it a try and made a believer out of him, he was amazed at how much better the fork felt.

    As a rule, a heavier weight will slow your dampening, lighter oil will do the opposite. Back in the day before forks had external dampening adjustments this was how you made an adjustment, now you just turn a knob.

    Anyway, whenever I change the fork oil in either my XC bike or my trailbike I use the same weight oil that came in the fork as they both have external damping adjustment. I figure the manufacturer designed the damping circuits to run with that viscosity so I go with it.

  7. #7
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    The only reason to really consider changing from what the stock oil weight is as standard is if you are heavier or lighter than the 'average' rider. I have put 15wt in most of my forks because of the fact that I am about 230lbs all in so the stock weight just isn't enough to really control my forks damping (although my '99 SID's are untouched internally)
    Do people think you are strange??

    Do you??

    ....Then you may be on the right track.
    (Rev. J.R. Bob Dodds)

  8. #8
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    Quote Originally Posted by tojnom
    How does oil weight affect fork performance (rebound, compression)?
    5wt vs 10wt vs 15wt, etc...

    My fork recommends 15wt, but I plan on experimenting with a couple different weights.
    If you're using anything but the OEM labeled oil......it's best to look at the oils viscosity instead of weight. Most oil manufactures will list this data.

    The higher the weight number the more resistance or force needed to cause the fluid to flow. So it would affect rebound and compression....depending on your fork type. Check this site out....Peter has a wealth of information on his website

    http://www.pvdwiki.com/index.php?title=Suspension_Fluid

  9. #9
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    replaced oil today

    So I replaced my fork oil today with SRAM's PitStop 10wt. Took it out for a test drive and what a difference! I also replaced the damping cartridge, air piston and shaft bolt o-rings. Pumped the fork up to 80psi and it feels like a new fork again. Very responsive, compression/rebound seem adequate. Anyone debating doing maintenance on their fork should give it a shot.

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