Another fork oil question

[blackhawkxx]

I know to measure the fork oil level, you should pull the forks. But, if you wanted to measure the level with the forks on (spring out), the tubes are at a angle, could you measure the low side of the oil and the high side and average them to get the correct measurement?

[tomek]

Yes,I understand they should be fully compressed for this operation.

[BackStreet]

Just have someone else with the same setup do the same measurement. You want both sides even too.

You can add some an oz if you are worried. Today's forks don't usually need oil added unless the seals are bad.

[RXX]

You know, I have been thinking about this too..... I just got a set of used forks and put them on before I checked the oil level (they had only about 4K sonce Racetech rebuild, so I didn't think it necessary)

Then I read the fork rebuild thread and wish I had changed the oil, but no fucking way do I have time now.

It SEEMS to me that since the height of the oil is supposed to be 139 mm (or something like that) when the forks are vertical, the a bright guy could figure how high it should be at any angle. I am thinking about calculating this and then doing the overfill/vacuum method described in the thread. It has just been so long since my trigonometry class that I am skeptical of my ability.

Any high-schoolers on this board??

[jon haney]

You know, I have been thinking about this too..... I just got a set of used forks and put them on before I checked the oil level (they had only about 4K sonce Racetech rebuild, so I didn't think it necessary)

Then I read the fork rebuild thread and wish I had changed the oil, but no fucking way do I have time now.

It SEEMS to me that since the height of the oil is supposed to be 139 mm (or something like that) when the forks are vertical, the a bright guy could figure how high it should be at any angle. I am thinking about calculating this and then doing the overfill/vacuum method described in the thread. It has just been so long since my trigonometry class that I am skeptical of my ability.

Any high-schoolers on this board??

BB forks are 43 mm outside diameter. Assuming 2 mm thick walls you would have 39 mm I.D. Take half that for the adjacent side of a right triangle or the length of the "B" side. The "a" angle will be the fork angle or IIRC 25 degrees. This makes the "b" angle 65 degrees and the "c" angle is always 90 degrees.

The formula is: A/sin a=B/sin b

To solve for A use...........Oh screw all this crap!! Just measure the low side of the fork and deduct 9 mm from what the book says. That should be close enough.

[blackhawkxx]

I was thinking if one side was let's say 150mm and the other 130, add them together 280 and divide by 2 to get 140. Most likely not that easy. Where are the math guys when you need them.

[runner]

I just change the oil and don't worry about measuring from the top. Measure what comes out and it should be close to what is required per leg (I usually let it drain a full day). I picked this up from a previous forum question... the allen bolts for removal are in the axle tube hole...worked great for me.

[jon haney]

I was thinking if one side was let's say 150mm and the other 130, add them together 280 and divide by 2 to get 140. Most likely not that easy. Where are the math guys when you need them.

I'm such a tard! Yes, you can do it that way. You don't need us math guys, we'll just over-think it. :icon_doh:

[blackhawkxx]

Yes, you can do it that way. You don't need us math guys, we'll just over-think it.

Thanks math guy.