I have about 4500km on my Fox 34, which I bought to replace my previous Rock Shox Revelation RC. The Fox is a good 150g lighter, but also feels like more of a true XC fork when compared to the beefier Revelation / Pike with 35mm stanchions.
The fork left the factory as a 120mm Performance Elite with the FIT4 closed damper. I have been changing the lower leg bath oil every 50-100h and even had to have the slide bushes replaced due to excessive play at around 3000km. Recently the fork started to feel strangely harsh and would also stiffen up considerably in freezing temperatures, so I decided to do a full overhaul apart from seal replacement.
I replaced the original 120mm air spring with the updated EVOL 130mm air spring when the fork was new. The old spring had the usual heavy dose of grease from the factory, which I cleaned up a bit when installing the spring and it has been trouble free ever since. However, as the fork started freezing up recently I knew it was time, or more likely long over due, to clean and re-lubricate the spring. I was right, the RSP Slick Kick I use had accumulated a hefty amount of water and turned into a mayonnaise like substance.
Servicing the air spring is easy when you have the lower legs off. Let the air out, undo the top cap and remove a circlip at the bottom of the left leg, which holds the air spring in place, and pull the piston assembly out. Clean and re-grrease, and you're done!
Many people are weary of changing the damper oil in a FIT4 damper, as it's a sealed, bladder type unit, which requires bleeding. The Fox instructions are nicely done and explain the procedure well. The only special tool required is a syringe that will seal against the top of the damper. I bought a suitable size syringe from the pharmacy and use a small o-ring for an additional seal.
The procedure is simple: You remove the lock-out lever, and under it you will find a small protruding shaft, which has a hex grub screw in the center. Undo the grub screw, and pour the oil into a container while remaining mindful, that there is a metal ball under the screw that will fall out with the oil, so don't just pour the oil into a huge container! I used a small plastic cup and fished the ball out with a magnet. Cycle the damper a few times to drain all the old oil.
Filling is when the bleed procedure comes in. Fill the syringe with oil, fully extend the damper and place it in a vice with soft jaws. Place the cylinder in the top hole and push in as much oil as you can. Then carefully cycle the damper while messaging the bladder, but don't fully extended the damper before the bladder has filled with oil, or it will suck itself in and you need to restart the process. Once no more bubbles are raised into the syringe when you cycle the damper, extend it fully and mark the shaft approximately 75mm from the top with tape. Then push the shaft in untill the tape meets the bottom of the damper and you're done. Remove the syringe, fill the top hole and shaft completely, place the ball back in the shaft and re-install the grub screw.
The lesson here is: Follow the manufacturer's service interval, or even if you don't, try not to exceed the recommended intervals by 10x!
The fork left the factory as a 120mm Performance Elite with the FIT4 closed damper. I have been changing the lower leg bath oil every 50-100h and even had to have the slide bushes replaced due to excessive play at around 3000km. Recently the fork started to feel strangely harsh and would also stiffen up considerably in freezing temperatures, so I decided to do a full overhaul apart from seal replacement.
Air spring
Servicing the air spring is easy when you have the lower legs off. Let the air out, undo the top cap and remove a circlip at the bottom of the left leg, which holds the air spring in place, and pull the piston assembly out. Clean and re-grrease, and you're done!
FIT4 damper
The procedure is simple: You remove the lock-out lever, and under it you will find a small protruding shaft, which has a hex grub screw in the center. Undo the grub screw, and pour the oil into a container while remaining mindful, that there is a metal ball under the screw that will fall out with the oil, so don't just pour the oil into a huge container! I used a small plastic cup and fished the ball out with a magnet. Cycle the damper a few times to drain all the old oil.
Filling is when the bleed procedure comes in. Fill the syringe with oil, fully extend the damper and place it in a vice with soft jaws. Place the cylinder in the top hole and push in as much oil as you can. Then carefully cycle the damper while messaging the bladder, but don't fully extended the damper before the bladder has filled with oil, or it will suck itself in and you need to restart the process. Once no more bubbles are raised into the syringe when you cycle the damper, extend it fully and mark the shaft approximately 75mm from the top with tape. Then push the shaft in untill the tape meets the bottom of the damper and you're done. Remove the syringe, fill the top hole and shaft completely, place the ball back in the shaft and re-install the grub screw.
The lesson here is: Follow the manufacturer's service interval, or even if you don't, try not to exceed the recommended intervals by 10x!
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