Monday, April 16, 2012

TECH: Part 3 of 4 - How to replace seals, oils, and re-assemble

OK, so you gave it some thought about having someone else do the work. Now you are reading this because you want to get your fork working perfectly for the 2012 season.

This is going to be a long 2 part post; separated into how to disassemble your fork and remove the seals and then where to put new oil, how to bleed the FIT cartridge and then how to reassemble.  If you have any doubts or your fork is not exactly the same as my (due to different year or slight model difference) please refer to

Another good resource is the Enduro Fork website:

The fork being used for demonstration will be a 2011 Fox F100 RLC FIT. All Fox forks with the FIT cartridge will be similar. For non-FIT versions it is actually simpler. I'll try my best to point out where you need to do something different for a non-FIT version.

First order of business. You need a clean working bench. This means vacuum up all the metal shavings from the last time you cut a fork steerer tube down to size. Clean up all the loose tools and such.

Now grab your notepad and a pen. Get your shock pump and install it onto the shreader valve and read the pressure in the air spring. Write it down. Now go to your rebound damping knob, start counting each click as you turn it clockwise. Write down how many clicks it took to get the knob to stop clicking. Now do the same for the low speed compression dampening and also the lockout threshold.

Once you have all your settings written down, adjust all the settings to the mid point.

The next step is to separate the lowers from the stanchions & crown. To do this you have to remove the two nuts at the bottom of the fork next to the quick release bosses. One side will have a red cap over it that allows you to adjust the rebound. You need to remove this red cap.

 To remove the red cap you need to loosen the set screw (2mm hex key) and pull the red cap off.

 The black nut is a 10mm hex nut. Take your 10mm wrench and loosen the nut.

Now take the black nut and invert it and screw it back onto the threaded shaft a few turns (don't screw it in all the way). Note the black nut has a plastic crush washer on the other side. Don't worry if you lose this used/old crush washer at this point in time, you will be installing a brand new one during the assembly. The brand new one comes with the fork seal kit from Fox.

Once you have all that done, take a small screw driver, a piece of paper towel and cover the shreader valve and depress the valve to release all the air out. Some oil will spray out and the point of the paper towel is to make sure it doesn't spray everywhere.

When you release all the air pressure from the air spring side the fork will compress (shorten). Now you have to dislodge the air spring shaft. Do so by tapping the nut with a plastic faced hammer.

Once the nut bottoms out remove the black nut, and take a long hex key and push the shaft all the way into the fork lowers as far as it will go. Oil will drain out, so have a container ready.

Now remove the black nut on the damper side of the fork the same way you did the air spring side. Once the black nut butts against the fork leg, remove the black nut and use an allen key to drive the shaft as far into the leg it will go.

The next step is to remove the two top caps from the fork. The hex size is 26mm. Take a 26 mm socket and carefully remove the top cap. Do this by applying pressure down socket so that there is zero chance the socket will skip off the top cap. The top cap is made from Aluminum and the hex height is very shallow so it can be easily damage if the socket slips.It doesn't matter which side you start first. I chose to do the damper side first.

Once you have overcome the torque and the top cap is loose. Un-thread the rest by hand.

Once you had the top cap loosened off completely from the threads in the upper crown you can pull the damper (aka FIT cartridge) straight out.

Now remove the top cap for the air spring side.

Tilt the fork upside down over your container to drain the Fox Float Fluid from the air piston side.

(Ignore the red inside the container, that was left over crud from another project)
Take an allen key and locate the end of the threaded shaft for the air piston side. This will push the air piston up, you will need to continue pushing until your fingers can grab the air piston out of the upper fork crown.

Once you have the fork broken down into its various sub-assemblies it looks like this. Take note that once your fork is taken apart you need to treat all the individual pieces with extra care. Treat time like they are fine china. DO NOT DROP THE CROWN/STANCHION onto the floor!

Now we begin to take the fork seals out of the lower leg.

You have two options.

1.) use small screw drivers and work the seal out of the bore and then chisel the seal out.

2.) Use the open end of an 18mm wrench to hook one jaw into the seal and pry up (This is what Fox recommends for the 32mm Talas forks.

Don't forget you can always use a combination of #1 and #2. It all depends on your luck. I used option 2 to get the seal dislodged from the lower fork legs. Once there is a gap I used a screw driver and tapped the seal out like I was using the screw driver as a chisel.

Don't this for both sides to get both left and right side seals out. The foam rings on both sides are found below the main seals. Remove those too. You will not be able to reuse these seals as they will be damaged during the removal process. They go into the garbage.

Now take everything to a big sink. Grab an old tooth brush and wash everything in hot soapy water.

Allow everything to dry overnight. If you can't wait make sure to towel dry everything.

Next post will deal with changing the oil in the FIT cartridge and reassembly. You will need to prepare the following oil volumes depending on your Fox Fork model and year.

Please let me know if you have any questions or if you find something that was confusing.

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