Fork oil level question.

[slipperymongoose]

Hi was wondering about what measure/comparison I use for my k3. My Haynes tells each fork has a capacity of 389cc and a level of 91 mm. Haynes tells me to pour then measure, but in the few threads ive gone through mention nothing about the amount you pour in. What do you guys usually do? Cheers.

[noiseguy]

Amounts seem about right. They only tell me how much to buy at the store, though.

I always measure the air gap to top... it's much more consistant then volume measurements. The air gap is what you're trying to control, ultimately... why not just measure it directly?

[slipperymongoose]

Cheers yeah I'll go that way and measure it.

[burning1]

Never rely on a volume measurement; always measure the air gap; only exception is when adding a small measured amount of fork oil in each leg to tune the performance of the forks (E.g. adding 10cc of oil to both sides.)

Air gap is an extremely critical measurement for fork performance; the air in the fork acts as a secondary spring, and relatively small differences in volume can have a huge impact on how the forks perform at bottom of travel. Two worst case scenarios is to over-fill the forks (causing them to become solid before they hit the bottom of travel, and likely blowing out the fork seals) and filling the legs to different levels (causing the wheel to pitch at bottom of travel.)

[burning1]

BTW... 91mm is fine with stock springs, but if you are going aftermarket, I'd suggest you lower the oil level to 120mm to start with, and go no higher than 100mm.

[slipperymongoose]

Yeah going .80 sonics.

[burning1]

Compare them to the stock spring. If they are anything like the racetech springs I ran, they are much longer than stock, and use much thicker coils. Because of that, they displace more oil. Since oil level is measured with the springs removed, it means that the oil level with the springs installed would be much higher than stock, and you should use the 120mm figure to start with.

[RichDesmond]

Yeah going .80 sonics.

115mm with the Sonic Springs.