Fork oil volume/level?

[BlackAndBlue]

Before I changed my fork oil today I did a search to find out how much I needed to put back in. I found a forum post that it took 497 mL per tube. I had a one liter container so I split it, almost all, between the two. The level looked kind of high; if I compressed the fork to the bottom, the oil would come very nearly to the top, within a centimeter. So it's back together now but when I got home I looked again. It seems that another number floating around is 465 mL or something like that. Some people measure it but I can't find a definitive method for measuring the level.

How do I do this??? I need to take the excess out tomorrow so it's ride-able again. I understand that too much fluid can cause damage.

 

[FinalImpact]

Depth is often times the stroke length of the fork. If both set to 5" you should be fine. Even 4.25" isn't the worst thing on used springs. But less than 4.0" and you the fork seals can suffer and the pressure shoots up inside when the forks bottom.

Spring out, compress fork. Measure depth.
Level: 134.0 mm (5.28 in)

Quantity: 467.0 cm³ (15.79 US oz) (16.47 Imp.oz)

 

[motojoe122]

A while back I bought a Motion Pro fork oil level tool. Once you know what level you need, pour in the oil, set the collar, and pull the syringe handle. View attachment 56698

 

[BlackAndBlue]

Is the measurement from the top of the tube to the oil level or from the bottom to the oil level?

 

[motojoe122]

Is the measurement from the top of the tube to the oil level or from the bottom to the oil level?

With the fork tool, you set the collar to the amount of fluid you want left in the fork tube and rest the collar on top of the tube.

 

[BlackAndBlue]

So 5" of measurement is more fluid than 4" then?

 

[FinalImpact]

So 5" of measurement is more fluid than 4" then?

Its from the TOP down (springs out, forks fully collapsed) so no... That is backwards. 4" down is adding MORE fluid volume and reducing air volume.

By adding more oil than the factory 5.28" depth, it reduces the static air volume. So, as the forks compress it effectively increases the spring rate.

 

[BlackAndBlue]

okay finally i understand now! thanks for helping me understand. so a little more than 467 ML is okay, but not much? I was able to just find the volume of a syringe and use that to remove oil down to what should be 467 ML or so now, just so i can ride it without risking damage but i may get one of those fork oil setter rigs and try to bump it up to 5" or so.

 

[FinalImpact]

okay finally i understand now! thanks for helping me understand. so a little more than 467 ML is okay, but not much? I was able to just find the volume of a syringe and use that to remove oil down to what should be 467 ML or so now, just so i can ride it without risking damage but i may get one of those fork oil setter rigs and try to bump it up to 5" or so.

FWIW: if installed on the bike the rake of the fork will upset your depth measurements. So error on the side of MORE fluid volume than less. i.e. 5.0" vs 5.3".

JM2C - but unless the forks are completely apart and assembled (dry so to speak), its a guessing game on fluid fill volume as you don't know how much is left inside. Hence measuring from the top down after purging the air is good choice.

You should be fine...

 

[BlackAndBlue]

Oh I see. Good point. That reminds me of advice I got one time to measure the fluid that you get out and put that amount back in. Ugh.