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How to do a Fox 36 Performance lower leg service in 9 easy steps

In this article I’m going to give you a step-by-step process on how to properly perform a Fox 36 Performance lower leg service.

Tools you need to do the Fox 36 Performance lower leg service

There are quite a number of tools you’re going to need, some of which are very specific to this operation.

Fox 36 Performance lower leg service repair specifications

damper oil amount
40 ml
air spring oil amount
10 ml
damper oil type
Fox 20 WT Gold suspension fluid
air spring oil type
Fox PTFE infused 5WT suspension fluid
damper crush washer diameter
13 mm
air spring crush washer diameter
8 mm

Step 1. Cleaning the fork

Before we open up the fork it’s incredibly important to clean it. If you receive a fork for a lower leg service, it’s never going to be 100 percent clean. Especially the steerer tube can hold a lot of dirt and sand.

cleaning Fox 36 Performance fork

Spray the fork copiously with bike cleaner. We use Muc-Off bike cleaner, but feel free to use any cleaner solution you prefer. By using a Pressurized spray bottle, it’s easy to get the stuff into every nook and cranny.

rinsing Fox 36 Performance fork

After you’ve used the bike cleaner and let it sit for a minute or two, rinse it off. Any method will do but a mobile outdoor cleaner will proof to be particularly helpful and efficient.

drying Fox 36 Performance fork

Make sure to dry the fork properly before moving onto the next step.

Step 2. Removing rebound adjuster

bench mount work stand

It’s recommended that for the next steps you use a bench mount work stand to be able to hold the fork while doing the Fox 36 Performance lower leg service.

removing rebound adjuster cap Fox 36 Performance fork

The rebound adjuster is protected by a cap. Before you can remove the rebound adjuster, you’ll need to remove this rebound adjuster cap.

removing rebound adjuster Fox 36 Performance fork

After the cap is removed you can remove the rebound adjuster itself by loosening the set screw using the 2mm hex key.

Step 3. Removing bottom nuts and crush washers

removing foot nut damper side Fox 36 Performance fork

Use a 10mm socket to remove the bottom nut located on the damper side. This is the side located on the right from the perspective of the rider.

removing foot nut air spring side Fox 36 Performance fork

Use a 15mm socket to remove the bottom nut located on the air spring side. This is the side located on the left from the perspective of the rider.

crush washer Fox 36 Performance fork

Both ends of the fork legs will have crush washers. Make sure you don’t lose these, if you’re going to reuse them.

Step 4. Removing damper and air spring

There can be quite some stiction between the bottom of the damper and air spring and the lower legs. So you’ll need to knock these out with a hammer.

removal tool

We use specific damper side and spring side removal tools to prevent the threads from damaging. Since these tools are really expensive, you can also use the sockets you’ve used to remove the bottom nuts.

removing lower legs Fox 36 Performance fork

With a gap between the fork leg and the removal tool or bottom nut of about 5mm give it a solid tap with a mallet. This should be enough to break it loose.

Step 5. Removing and cleaning the lower legs, damper and air spring

With the lower legs loosened you can rotate the fork to a standing position and remove the damper and air spring. Be sure to have your oil drain pan ready, because oil will be coming out of the fork legs.

boost thru axle Fox 36 Performance fork

Because only the fork brace keeps the loose lower leg in place, it’s a good practice to strengthen it using a Boost thru-axle.

Step 6. Replacing foam rings, seals, and sag ring

fox 36 dus wiper kit

We’re going to replace the foam rings, seals, and sag ring. To do so we need to remove the old ones first.

Using a long tire lifter, we can pop the seals and foam rings out.

Fox 20WT Gold suspension fluid

Pre-soak the foam rings, which we’re going to install later. Use a plastic container with Fox 20WT Gold suspension fluid.

cleaning lower leg Fox 36 Performance fork

Before we install the new foam rings you can clean the innards of the lower legs. Since this is a routine maintenance of a well-kept fork we only needed to clean the upper part.

replacing foam rings Fox 36 Performance fork

With the legs cleaned place the new foam rings into the lower legs using a pick to get them out of the plastic container.

Since the foam rings were lubricated when moved into place we don’t need any extra lubrication for the seals, since the foam rings have left enough on the insides of the lower leg. Using a Fox 36 seal driver tool we can then proceed to hammer the seals into place.

Step 7. Reinstalling damper and air spring

applying silicone grease Fox 36 Performance fork

Before reinstalling the damper and air spring put some silicone grease on the inside of the seal to aid in this process. We use Renolit SL 410 M silicone grease for this purpose.

installing sag ring Fox 36 Performance fork

Don’t forget to add the sag o-ring to the shaft before installing.

inserting damper and air spring Fox 36 Performance fork

It’s now time to very carefully insert the damper and air spring into the lower legs. Be careful not to damage the smooth walls of the lower legs during this process.

And also make sure that the damper and air spring go in correctly, with the air spring sitting on the left and the damper on the right. The damper is the side with the rebound adjuster.

It might take some moving back and forth before the air spring and damper actually go into the lower legs.

Step 8. Inserting oil into lower legs

rotating Fox 36 Performance fork for oil insertion

Next up is the oil insertion into the lower legs. To be able to do this its best to rotate the fork so the legs are pointing upwards for gravity to do its job when you put in the oil.

Be sure to move both damper and air spring out a little again so they don’t stick out of the lower legs, and the oil actually has some room to go into.

inserting Fox 5WT damper fluid into Fox 36 Performance fork

Put 40 ml Fox PTFE infused 5WT suspension fluid into the damper on the right using a syringe.

inserting Fox 5WT oil into Fox 36 Performance fork

Then proceed to add 10 ml of Fox 20WT Gold suspension fluid into the air spring side.

Step 9. Tightening bottom nuts

After you’ve pushed both rods out of the bottom of the lower legs, it’s time to put new crush washers on them if you do not plan to reuse these . You’ll need a 13 mm for the damper and 8 mm for the air spring. These crush washers are going onto the bottom nuts.

torque wrench for Fox 36 Performance fork

We use a torque wrench set at 7.4 Nm to tighten both foot nuts.

Use a 2 mm hex tool to put the rebound adjuster knob back into place. After which you can put the rebound adjuster cap back into place as well.

cleanup of Fox 36 Performance fork

A final cleanup with a bit of Muc-off Bike Protect and your Fox 36 Performance lower leg service is done.

bio vanseijen

Johan van Seijen


Johan van Seijen is the founder of His cycling career has seen him at the starting line of classics such as the Amstel Gold Race and Liege Bastogne Liege. Realizing his racing capacity would fall short of what was needed he obtained a MS from the University of Amsterdam in engineering. His love for cycling changed into riding in an amateur capacity with his local cycling club TFC Weesp as a roadie and supporting MTB Noordwest as a mountain biker. He repairs, restores, and builds bicycles and shares his knowledge on YouTube, Facebook and this website. 

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