Wednesday, May 23, 2012

Replacing Seals on a Fox RL Fork - The Missing Manual

Fox provides information on replacing the oil and seals for a F29 (i.e. Float 29er) RL or RLC fork shock here:  However, when I tackled this myself, on an RL model shock, there were quite a few things that were not adequately explained for a DIYer in Fox's instructions.  Hope this helps someone else who is wrenching on their own bike instead of taking it to a shop and rolling the dice on getting a capable mechanic.

Step 1 - Removing the rebound knob.
Note: I'm not the only one who had troubles here:
  • Fox's instructions fail to say what size wrench to use for the hex screw in the rebound adjuster knob.  I found the screw to be ver sloppy with a 2mm allen wrench, and too small for a 2.5mm allen wrench to fit.  All fittings on a bicycle SHOULD be metric, but in this case, a SAE 3/32" (which is about 0.094 inches, or about 2.4mm) fits much more snugly into the screw, reducing the chances of stripping out the head on the hex screw. 
    Note: For other poorly fitting hex screws you encounter, this chart is helpful:
  •  Fox's instructions fail to suggest how to hold the rebound knob to avoid damage to the fork's internals or the knob as you apply the torque necessary to loosen the hex screw.  This photo shows how I managed to get a grip on it using curved needlenose pliers and a piece of innertube with a hole punched in the middle.

Step 2 - Removing the lockout lever on the RL model shock.
  • The pictures in Fox's instructions show the lockout lever that uses 3 grub screws and retention balls. Newer RL shocks (2010+?) do not have the 1.5mm grub screws.  The lever is retained using a spring clip that expands into a slot inside the blue aluminum lockout lever.  It needs to be popped loose using a hammer against a soft-material drift that won't scratch the lever or the crown on the fork.  I used a short piece of thick-walled 1" PVC pipe (plastic), but a wooden dowel would also probably work.  
  • It would also be useful to remember how the lockout lever aligns with the hex shaped end of the hollow adjustment shaft.  Before removing the lever, it might help to use a scoring tool to make an alignment mark on the flat side of the shaft that lines up with the handle of the lever.
Here's what the inside looks like so you know what you're trying to pop

Step 3 - Removing the Top Cap
The only tip here is that although Fox's instructions say you might want to grind down a 26mm socket so it will mesh better with the wrench flats on the top cap, they don't mention _how_ to grind down a socket or specifically what grinding makes a difference.
  • HOW:  If you have a socket driver bit for a drill that's the right sized for the 26mm socket, you can spin the socket against coarse sandpaper with a high speed drill for 10 or 15 minutes (depending on the hardness of the socket's metal).  If you're using a battery powered drill, be sure you switch it to "drill" speed instead of "screwdriver" speed or it could take WAY longer to grind the socket down.  
  • WHY: Fox's picture shows a bevel on the outer edge of the socket, which might seem like a good idea to keep from scratching the finish on parts of the fork _around_ the top-cap.  However, that's NOT the point of grinding it down.  Many sockets are made with a bit of a bevel on the _inside_ edge that serves as an alignment ramp, making it easier slide the socket onto normal nuts or bolts.  That beveled part might be a few millimeters deep, which is not a concern for normal nuts and bolts.  However, unlike a normal nut or bolt, the fork's top-cap wrench faces are only a few millimeters thick.  That means a typical socket might only engage the top-cap's wrench faces with the beveled part, giving it a very sloppy grip on the part.  The point is to grind the end of the socket down past the bevels, so that the socket's inner faces are exactly 26mm, all the way to the leading edge, giving a solid mesh between the socket and the top-cap.
  • After you have the front edge of the socket ground flat, then you could also bevel the outer edge to prevent scratching the fork, or to make the socket smoother to handle in the shop, but that part probably isn't entirely necessary.
Here is a photo of the 26mm ground down socket (on the left) and another socket that has not been ground down.  Notice the cupped bevel on the not-ground-down socket (on the right) and the flat, abrupt inner edges on the one that is ground down to get a firm grip on the fork's top cap.

 More to come when/if I have a chance to help one of my riding buddies replace the oil and seals in their Fox fork/shock.  The rest of Fox's instructions were okay regarding the "how" part, but still left out a lot of the "why" part.

A company called Real World Cycling makes aftermarket seal kits for quite a few shocks/forks.  Their product is named Enduro seals (not to be confused with the Specialized bike model).  It might help fill in some gaps to take a look at their instructions for replacing the seals.  Their products seem to be a pretty good alternative to the stock Fox parts too.
 If you order something from Real World Cycling, tell them you found their products from this blog post and maybe they'll send me a shirt or a hat.


cmh said...

Thank you! I was looking at the same directions and wondering where the hell the set screws were. I did some gingerly prying but not too much, but then I found your writeup and with a little more gusto, pried it right off.

Whirly said...

cmh, Glad you got it apart. Hope the rest of it went well. It makes me wonder if those little details they (Fox) left out (or never bothered updating) are really just their passive aggressive way of trying to keep us from fixing our own stuff using better parts. As an update, the aftermarket (RWC) seals I installed, instead of using the original Fox part, work better, and have held up WAY better than the originals.

Christopher Opie said...

Thanks for the super informative article! Question: have you ever found any sockets that have that flat edge naturally? Also what tool would you recommend for grinding down normal sockets?

Whirly said...

No, Christopher Opie, I have never seen any sockets made without the bevel. Since most sockets are tool steel, i.e. VERY hard metal, I would recommend just using medium grit sandpaper meant for use on metal, on a belt sander if you have one available.