The Golden Wrench

A blog about bicycle repair and maintenance by the mechanics at Freewheel Bike.

Tuesday, September 20, 2011

Bring in your Fox FiT forks!

Here at Shockspital I finally got the chance last week to do a full overhaul on a Fox fork equipped with their new FiT cartridge damper. We haven't seen many of these come through for service yet because they're so new--Fox only starting putting FiT dampers in their 32mm forks in 2010. But if you're following Fox's recommended service intervals, those 2010 forks are due for some love.

But back to my story: At the Murphy Menace 50-mile MTB race that Freewheel sponsored at the end of August we gave away several fabulous door prizes. Among them were some gift certificates for a full suspension fork overhaul! One of these lucky winners brought in his Fox F-series FiT RLC for us to freshen up. Here is a shot of the FiT damper once we got everything apart:

The shorter gold rod on the left is the coupler that holds the bladder assembly together. Just to the right of that is the black bladder which allows for volume changes as the fork moves through its travel. Just under that is the compression piston and the shim stack which controls oil flow through said piston. On the right is a longer gold shaft which is part of the rebound assembly. But of course that's not all one big piece; here's the guts:

At the top right, sporting the pink glide ring, is the rebound piston. At top left is the adjuster which is the only part of this assembly which is visible from the outside of the fork (though typically it's mostly covered by the red rebound adjuster knob on the bottom of the fork leg). As you spin that knob it moves the threaded portion of the adjuster, which in turn pushes the small silver shaft up through the larger gold shaft. As you thread the adjuster further in it causes the needle on the opposite end of the shaft to close the central port of the rebound piston, which increases the rebound damping and causes the fork to rebound slower because of the restricted oil flow.

I'm not going to go into the procedure necessary to get this entire assembly back together with no air bubbles in it. I'm sure you can imagine. But that's one of the benefits of this closed-cartridge system: it's much better than an open-bath system at resisting cavitation and contamination, both of which affect the performance and longevity of your suspension components.

One important point here is that this fork was still performing fairly well. The damper was still in good shape and the oil was pretty clear. But now with fresh oil and new seals this fork should run smoothly all through next season, too. And by having his fork serviced before any major problems manifest, this customer is helping ensure that it will perform at its best for many seasons to come.