Fox F120 RL - low psi = low travel?!

I'm having some issues with my fork and I'm not sure whether its normal or not..
Just got a F120 second hand, changed the oil in damper side (10w), cleaned seals & wipers and relubed with 80w etc. I.e. a semi-full service/rebuild.
I'm 5 foot, 6 inches and weigh a measly 50kg. Now, setting my ideal pressures for 20-25% sag (40-50psi ish), I find that the fork doesn't quite fully extend to 120mm. It's lost about 5-10mm. Higher pressures (70psi +) and the travel maxes out to 120mm.
Now I swear my other F120 on a different bike has a constant 120mm even at 40psi? The only thing I can think of to justify the difference is that I might have put a tad too much 80w in the top air-side chamber (I'm talking 8ml instead of the recommended 5ml!).
Is there something wrong? I'd rather not take it for a £100 service, re-building it wasn't all that difficult. :? :? :?
Just got a F120 second hand, changed the oil in damper side (10w), cleaned seals & wipers and relubed with 80w etc. I.e. a semi-full service/rebuild.
I'm 5 foot, 6 inches and weigh a measly 50kg. Now, setting my ideal pressures for 20-25% sag (40-50psi ish), I find that the fork doesn't quite fully extend to 120mm. It's lost about 5-10mm. Higher pressures (70psi +) and the travel maxes out to 120mm.
Now I swear my other F120 on a different bike has a constant 120mm even at 40psi? The only thing I can think of to justify the difference is that I might have put a tad too much 80w in the top air-side chamber (I'm talking 8ml instead of the recommended 5ml!).
Is there something wrong? I'd rather not take it for a £100 service, re-building it wasn't all that difficult. :? :? :?
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05 Spesh Enduro Expert
05 Trek 1000 Custom build
Speedily Singular Thingy
I'm around 5'4", skinny, and still weight 55kg or so.
05 Spesh Enduro Expert
05 Trek 1000 Custom build
Speedily Singular Thingy
Now, two things. I'm not convinced a few mls too much on the spring top side would have an affect, but I'm no expert; surely quickly whipping off the top cap and emptyin the oil would let you test this. If it works only put 5 mls back.
Second, I went with 10w rock oil as it happens to have a similar centi-stokes rating as the overpriced fox stuff. I assume you have too. Now, I've been concerned that light spring pressures might necessitate a lighter damper oil, and my inexpert theory is that your spring pressure is too low to overcome the rebound damping. Might be worth considering lighter damper oil.
Last thing is it's prob worth giving the fork a bed in period post-service to see if it settles down once the oil has found it's way aroun the fork.
Phil
Change the volume of oil, check for improvement, if not then up the pressure to the minimum as that cant be helping either. If you dont like them that firm then those forks aren't for you.
I used Silkolene Pro Fork Oil 10w for damper side. Pretty sure I got the oil volume as I used syringes to measure. Same colour as fox and apparently its just rebranded and had the classic Fox-tax. For Fox Fluid I used Silkolene 80w Gear Oil (which cost about 25% of Fox Fluid, again rebranded stuff. Heck if you used Redline Gear Oil it's even blue to match).
I don't think it's rebound from the slightly weightier oil (old oil must be 7w) cos the damper side shouldn't affect travel, just the rate of rebound & damping. Plus, if I open the rebound damper fully, it still suffers the same problem. With the rebound being adjustable, you can counter the heavier oil. I can't see how the oil volume in the damper side can affect the travel according to psi.
I have another pair of F120's, same year (2009) on my full-sus Trance and it works perfectly.
:twisted:
Did you manage to figure it out? I reckon my original guess of too much oil in the top air chamber as that's the only chamber where air is under pressure. I'll give it a good seeing to later in the week and report back.
That's what they said to me. I'm just waiting to call the service centre to see if that will be covered under warranty.
05 Spesh Enduro Expert
05 Trek 1000 Custom build
Speedily Singular Thingy