[tuumbaq]

I need help figuring this one out....So Im on a 2011 Fox40 and Ive tried 3 different fork oil to rebuild the cartridge .Overall the fork is smooth, rebound works like a charm but the compression just isnt there , the fork dives a lot and if very soft.I did rebuild it once a few months ago with the proper Fox 10 wt RED fork oil and it was just as good as new but didnt have the red stuff this time.

Ive tried Maxima 10 wt, Fox SUSPENSION fluid 7.0wt(maybe a bit closer to how it should feel ?) and the FOX green 10wt as well (seems to be the softest)

Before I go and buy some red Fox oil I'd still like to know if it could be something else , something I may be able to fix myself or would it need to be repair by a pro...Dont see what or how it could be broken but its certainly not performing the way it should.

Im sure the viscosity of oil can have an affect on the compression but could it be THAT noticeable

 

[Udi]

Stock oil is Fox RED (Silkolene Pro RSF 10wt, 47cSt), not sure why you're trying all these other oils. I found there was ample compression damping on both the 2011 and 2012 fork with this oil, however the adjuster settings had to be fairly firm.

What are your compression adjuster settings (clicks out from closed, HSC and LSC)?

Body weight and spring rate?

 

[Norther]

Oil viscosity does have great affect on damping that is obvious. When setting older Marzocchis that was the only way to adjust compression damping. I would say that if you double the viscosity, you will double the damping effect also. IF the fork is ok.

Maybe there is something wrong with your fork? Have you bleed the cardridge properly? Last week my friend lost suddenly most of the compression damping from his Fox 40. He'll send the fork to service asap, I am keen to see what happened. The fork started to compress way too easily and it dives easily almost through it's whole travel.

 

[tuumbaq]

Ive rebuilt it again this morning and altough the compression does seem to work when hand holding the damper once its in the fork , it doesnt do much.

I now get over 40% of sag with the same blue spring (Im 150lbs)and I used to be getting 25%...this is really weird to me and makes not sense.Spring is fine as well...

_Udi, thanks bro but Im not looking for tuning tips at this point, Ive had the fork for nearly a year now and I know what its suppose to feel like.Even with both HSC and LSC fully closed, its still sags a lot and is uber softIm not trying to experiment either with different fork oil, Im using what I have on hand right now...Something I find interesting is that Ive used the same Maxima 10wt in my previous 40's (which had far less compression to start with ) and it was fine but doesnt seem to do so well in the new one . . .

Im seriously starting to think there must be something wrong with it...I can EASILY bottom out the thing in my garage and thats @ max compression...Id be curious to hear what happens to your friends fork Norther...

 

[Udi]

I didn't offer you tuning tips, I asked what your current settings are. Just trying to help.

I do know for a fact that useful compression damping is minimal unless the HS is wound in a fair way (I have mine fully closed), because the assembly blows off too easily otherwise.

The oil volume in the 40 cartridge is minimal, which is why Fox uses the Silkolene RSF oil in the first place (the shock fluid is more temperature stable), the Maxima stuff may not be filling this requirement.

FYI, the viscosity of the fluids are using are as follows:
32 cSt Maxima Racing Fork Fluid
32 cSt Fox 7wt / Torco RSF Medium (no longer used in any Fox fork)
47 cSt Fox RED 10wt / Silkolene Pro RSF 10wt
47 cSt Fox GREEN 10wt (IIRC, value is written on bottle if you want to double check)

So - most of the fluids you're using are thinner than stock, thus you would have less damping than intended - likely a noticeable difference too. Green oil is for lubrication in FIT forks (not damping), if you're going to the trouble of buying that stuff, I think you should buy the Red as well (or Silkolene equivalent).

So, possible problems:
- You're using too light an oil
- You're not bleeding the cartridge properly / air is left inside
- There is something wrong with your cartridge

It would be fairly obvious if the cartridge was busted (and you seem to imply it cycles well in hand), but it's hard to diagnose that over the internet. My suggestion would be to use the correct oil, follow the Fox instructions for the 2011+ cartridge to the dot, and try again. I'd max out both compression adjusters for good measure when testing, because your fork should feel very firm at that setting.

If (after trying) that is not your experience, then I'd say something is wrong inside the cartridge. Best sent to Fox, or if you must DIY, purchase the clamp set/s and inspect inside.

 

[Udi]

I now get over 40% of sag with the same blue spring (Im 150lbs)and I used to be getting 25%...this is really weird to me and makes not sense.Spring is fine as well...

Im seriously starting to think there must be something wrong with it...I can EASILY bottom out the thing in my garage and thats @ max compression

That part is pretty weird for sure, I weigh more than you, and I don't think I can bottom out the blue spring even with the damper removed entirely. Have you inspected the entire spring leg, including the spring rod?

If you're bottoming the thing out easily in your garage like you say, I'd suspect something is very out of order.

 

[tuumbaq]

I didn't offer you tuning tips, I asked what your current settings are. Just trying to help.

I do know for a fact that useful compression damping is minimal unless the HS is wound in a fair way (I have mine fully closed), because the assembly blows off too easily otherwise.

The oil volume in the 40 cartridge is minimal, which is why Fox uses the Silkolene RSF oil in the first place (the shock fluid is more temperature stable), the Maxima stuff may not be filling this requirement.

FYI, the viscosity of the fluids are using are as follows:
32 cSt Maxima Racing Fork Fluid
32 cSt Fox 7wt / Torco RSF Medium (no longer used in any Fox fork)
47 cSt Fox RED 10wt / Silkolene Pro RSF 10wt
47 cSt Fox GREEN 10wt (IIRC, value is written on bottle if you want to double check)

So - most of the fluids you're using are thinner than stock, thus you would have less damping than intended - likely a noticeable difference too. Green oil is for lubrication in FIT forks (not damping), if you're going to the trouble of buying that stuff, I think you should buy the Red as well (or Silkolene equivalent).

So, possible problems:
- You're using too light an oil
- You're not bleeding the cartridge properly / air is left inside
- There is something wrong with your cartridge

It would be fairly obvious if the cartridge was busted (and you seem to imply it cycles well in hand), but it's hard to diagnose that over the internet. My suggestion would be to use the correct oil, follow the Fox instructions for the 2011+ cartridge to the dot, and try again. I'd max out both compression adjusters for good measure when testing, because your fork should feel very firm at that setting.

If (after trying) that is not your experience, then I'd say something is wrong inside the cartridge. Best sent to Fox, or if you must DIY, purchase the clamp set/s and inspect inside.

thanks man , I normally use the Red oil from Fox as well but the shop Im getting it from arent open during the weekend and was hoping to fix it before Monday...This is good info, I was under the impression since the cartridge doesn require much oil it wouldnt have as much of an affect on compression but I guess its the other way around . . .

According to this chart :

http://www.peterverdonedesigns.com/files/suspension oils.pdf

the viscosity of the different oil Ive used seems a bit closer to the Silkolene but Im a bit confused and Im not sure Im reading it right...your numbers are significally different, so I'll take your word for it as it makes more sense.

I too ,think it would be fairly obvious if the cartridge was busted and the bleeding procedure is pretty straight forward...hard to do something wrong I'd say, I'll try to source down a "thicker" oil today and give it another go ...I already have the clamp and I intend to do a complete disassembly this time, thanks again !

 

[Udi]

No worries.
On that chart you linked, you're looking at the blue line (cSt@40), but the chart is very hard to read. This one is a lot easier.

Not sure if you read my second reply, but are you sure you can bottom it out in your garage, like use 203mm of travel (via o-ring or whatever)? Because that sounds like something is wrong in the spring leg perhaps, also because you mention the sag has changed.

The springs can break (updated in later 2012 forks), I think it'd be worth carefully inspecting the spring / spacers / spring rod as well. Just to be sure.

 

[buckoW]

I think you should try another blue spring even if it isn't broken. I had a buddy with a weird feeling extra soft blue spring that looked normal. That sounds like the same issue.

 

[tuumbaq]

I think you should try another blue spring even if it isn't broken. I had a buddy with a weird feeling extra soft blue spring that looked normal. That sounds like the same issue.

Interesting to know, I broke one of my blue spring last week and then since been running a replacement spring...I started to rebuild my cartridge with random oil at the same time, it could be this as well, thanks