Fork Service (Fox F120 RL)

All photos below are taken with my Panasonic GF3 and 14 f/2.5 (in a dimly lit bicycle storage room).

I was planning to try my first DH/FR turns for the season today (and the first since I broke my wrist last autumn) but the weather turned worse again and I decided to do a long overdue service of the fork on my trail bike instead. It’s a Fox F120 RL, got it with my Giant Trance X3 in 2009 and I haven’t touched it since. Seeing how the forks on my FR bike (Rock Shox Domain and Boxxer) seems to need a service every couple of days I figured it was time I had a look at the Fox also.

Fox have some sort of service manual on their web site. The procedure is similar to servicing a Rock Shox (which I’m getting quite comfortable doing), but one difference is that my Fox is an open bath fork and you can’t clean and lube the lowers without pouring out all the oil on the damper side, 160 ml (here is a direct link to the oil volume chart in the service manual).

Lowers off.

Damper out in the open.

Air spring and damper.

The oil actually look ok even though it was almost 3 years old. I didn’t change any o-rings or other parts, just cleaned everything and replaced the oil but I think I should replace the foam rings in the lowers soon, they start to look a little worn.  The whole exercise went smoothly except for when I was going to tighten the topcap on the damper side. The wrench slipped and there was a slight damage to the edge holding the lockout switch in place. The switch still runs smooth, maybe it’s a bit more loose than before, but I hardly ever use the lockout anyway so I don’t really care.

Since I have a one Fox and two Rock Shox forks I didn’t want to spend money on two different brand specific fork oils and instead I have bought two weights of Motorex Racing Fork oil, 2.5 W and 10 W (bought mine from With those two and a chart showing viscosity for different oil brands (I use this one from Peter Verdone) I figured I could mix together a suitable weight. This time for the FOX I didn’t bother and just used the Motorex 10 W. For the air spring I used Red Line Transmission oil (don’t have the bottle in front of me so I can check the weight).

Rebound and lockout worked when I put everything together again (always nice when that happens), will see if the fork feels any different when when I take it out for a ride the next time.

Ready for new adventures.


3 thoughts on “Fork Service (Fox F120 RL)

  1. Rock Shox är jag mer eller mindre expert på nu 🙂

    Typ samma princip på Fox också, lättare än vad jag trodde att det skulle vara. Inte lika enkelt att göra snabbservice och bara göra rent i ytterbenen (men när det är open bath behövs det väl inte lika ofta heller).

  2. The fork seems to be working good. I guess the open bath construction and larger oil volumes compared to my Rock Shox forks (160 ml on the damper side and 30 ml on the spring side) means it’s not as critical to do regular service. There not much risk of the fork running dry in the lowers, just if the oil gets contaminated.

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