fork oil height

5 replies to this topic
  • Guest_mxrider426_*

Posted May 16, 2002 - 08:36 PM


Does anybody know how to check your fork oil height with the forks on the bike?

  • moorespeed426

Posted May 16, 2002 - 08:51 PM


just pull the caps and fork springs out and collaspe the forks all the way and measure from the top of the tube

  • sirthumpalot

Posted May 17, 2002 - 12:15 AM


Get one of those fork oil tools or make one yourself (syringe with a tube). Well worth the cash IMHO.

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  • Mark_Cantrell

Posted May 17, 2002 - 06:19 AM



I'm going to draw a lot of fire here, but you can't measure the fork oil height in the forks. I'm new to suspensions but talked to Steve at Factory Connection last night about this very topic. To measure the fork oil height, you need to:

1. Loosen upper triple clamp pinch bolts.
2. Loosen end cap (bolt around rebound adjuster).
3. Take off forks (shields, brakes, odo, axle, wheel, etc.)
4. Unscrew fork end cap bolt, outer tube will slide down.
5. Pull spring and metal cup down, insert 17mm open end wrench over metal cup, below plastic washer. Unscrew end cap from dampening rod.
6. Lift off end cap, bushing, plastic washer, metal cup, and spring. Push dampening rod and outer tubes all the way down.
7. Fill to top of outer threads with fork oil.
8. Work damper rod at least 10 times. You will hear air/oil slurping. Keep oil topped off to top of threads.
9. Work outer tube up and down but no more than 8 inches or it will introduce more air. Keep oil topped off to top of threads.
10. WOrk damper rod 10 more times, it should have steady resistance all the way up and down. Probably won't need more oil.
11. Use suction tube (I got a Motion Pro for $29 at local parts house) to suck oil down to desired level (I went back to 130mm from 145).
12. Pull damper rod to top, slide on spring, put metal cup over spring, put 17mm wrench on hex part of damper rod, put on plastic washer and screw on bushing/end cap. Torque to spec.
13. Pull up outer tube, screw tube onto endcap, hand tight.
14. Slip tubes up triple clamp, temporarily tighten lower pinch bolts, torque end cap (will probably have to loosen or remove bars, loosen pinch bolts to retorque and torque all 3C pinch bolts.
15. Reinstall brake, shields, odo, wheel, axle, and axle shield.
16. Reinstall bar if necessary.

Notice that before we could measure, we had to fill all the air spaces in the innards of the fork. That's why I said you can't measure it. If you measure the oil (remove forks and springs, slide outer tube and damper rod all the way down, you will measure between 15 and 25mm too high. Varying amounts of air are trapped in there. You have to adjust it instead of measuring it.

I did this (and changed the oil while I was in there) last night and it took about 3 hours and was pretty messy. Next time, I will put Visqueen on the floor before I start. I know people measure the oil all the time but the result is useless. Again, I'm going to take heat on this and someone may know better.

Someone may have a 'trick' that lets you do it. But be careful, 15-25mm is way to much to chance. If you're not sure he knows what he's talking about, do it this way. Even if you can't trust me, you can trust the manual and Steve at Factory Connection. They both agree on this.

Good luck,

  • DaveJ

Posted May 17, 2002 - 07:00 AM



Springs out, forks collapsed. Both air and oil will hide in the system so there are endless tricks to make things equal.

The old method of setting height was flashlight and ruler (err...dipstick). The better method is a sunction tool with a ruler built in. Motion Pro has a good one, or you can build your own.

In the real world, we care about how the bike rides. Therefore, we add and remove oil in equal amounts via the bleed holes. Position your forks accordingly in the triple clamps.

But it's always worth at least knowing where you started so you don't under or overfill.

By the way, (in my book) the rule is to start low, then add. You want good bottoming resistance, but too much oil won’t allow the front end to dive and turn.

However, if your style is all about jumping, then more oil will ease your medical bills.

Hope this helps!


  • Guest_mxrider426_*

Posted May 17, 2002 - 07:31 PM


Thanks you guys for your advise. I think I will make one of those fork oil tools

[ May 17, 2002: Message edited by: mxrider426 ]

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