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How to do a Rockshox SID Brain lower leg service in 17 easy steps

Table of Contents

In this article I’m going to give you a step-by-step process on how to properly perform a Rockshox SID Brain lower leg service.

Tools And Products You Need To Do The Rockshox SID Brain Lower Leg Service

There are quite a number of tools you’re going to need, some of which are very specific to this operation. In the table below you can find the steps involved, included the tools, products, and specifications necessary to perform them.

Action
Tool
Product
Specification
use bike cleaner
pressurized spray bottle
bike cleaner
rinse fork
mobile outdoor cleaner
dry fork
remove rebound adjuster knob
2 mm hex tool
remove rebound adjuster bottom nut or foot bolt
5 mm hex tool
remove air spring bottom nut or foot bolt
5 mm hex tool / 10 mm socket
loosen lower legs with removal tool
lower leg removal tool / mallet
remove lower legs
oil drain pan
install thru-axle
thru axle
remove seals and foam rings
fork seal removal tool
clean lower legs
shop towel
remove air cap valve cover
remove valve
valve removal tool
remove top cap
24 mm top cap socket / 3/8″ drive ratchet
remove internal retaining ring
retaining ring pliers
remove air spring
remove compression adjuster knob
2 mm hex tool
remove compression adjuster, spring, bearing, and ring
remove top cap with damper
24 mm top cap socket / 3/8″ drive ratchet
clean air spring
clean stanchions
pvc tube / shop towel
replacing o-rings
o-rings (from service kit)
reassemble air shaft
o-rings (from service kit)
reinstall air shaft
retaining ring pliers
install sag o-ring
sag o-ring (from service kit)
reinstall air cap
24 mm top cap socket / 3/8″ drive ratchet
reinstall valve
valve removal tool
reinstall damper
24 mm top cap socket / 3/8″ drive ratchet
reinstall compression adjuster, spring, bearing, and ring
reinstall compression adjuster knob
2 mm hex tool
pre-soak foam rings
lower leg oil / foam rings (from service kit)
install foam rings
install fork seals
35 mm seal driver tool / mallet
fork seals (from service kit)
reinstall lower legs
rotate fork
fill air spring side with lower leg oil
lower leg oil
10 ml
fill damper side with lower leg oil
lower leg oil
10 ml
install crush washers
crush washers (from service kit)
reinstall bottom nut or foot bolt
5 mm hex tool
reinstall rebound adjuster bottom nut or foot bolt
5 mm hex tool / 10 mm socket
tighten bottom nut or foot bolt and rebound adjuster
torque wrench
7.4 Nm
reinstall rebound adjuster knob
2 mm hex tool
reinflate air spring
suspension pump
100 Psi
reinstall air cap valve cover
clean fork
bike protect

Step 1. Clean The Fork

Use Bike Cleaner

use bike cleaner RockShox SID BRAIN fork

Before we open up the fork it’s incredibly important to clean it. If you have 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.

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.

Rinse Fork

rinse RockShox SID BRAIN 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.

Dry Fork

dry RockShox SID BRAIN fork

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

Step 2. Remove Rebound Adjuster And Bottom Nut

Remove Rebound Adjuster Knob

remove rebound adjuster knob RockShox SID BRAIN fork

Remove the rebound adjuster knob using a 2 mm hex key

Remove Rebound Adjuster Bottom Nut

remove rebound adjuster bottom nut or foot bolt RockShox SID BRAIN fork

Take out the rebound adjuster bottom nut with a 10 mm socket.

Remove Air Spring Foot Bolt

remove air spring bottom nut or foot bolt RockShox SID BRAIN fork

The air spring is tightened with a foot bolt. Using the 5 mm hex key, remove this bolt.

Step 3. Remove Damper And Air Spring

Loosen Lower Legs With Removal Tool

loosen lower leg with removal tool RockShox SID BRAIN fork

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.

We use specific damper side and spring side removal tools to prevent the threads from damaging. With the removal tool in place give it a solid tap with a mallet. This should be enough to break it loose.

Step 4. Remove The Lower Legs

Remove Lower Legs

remove lower legs RockShox SID BRAIN fork

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.

Install Thru-Axle

install thru axle RockShox SID BRAIN fork

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

Step 5. Remove Seals And Foam Rings

Remove Seals And Foam Rings

remove seals and foam rings RockShox SID BRAIN fork

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 fork seal removal tool, we can pop the seals and foam rings out.

Clean lower legs

clean lower legs RockShox SID BRAIN fork

Clean the parts where the seals and foam rings used to sit using a shop towel.

Step 6. Remove The Air Spring Shaft

Remove Air Cap Valve cover

remove air cap valve cover RockShox SID BRAIN fork

For now we’re going to leave the fork legs for a while and focus on the damper and air spring. Remove the air cap valve cover to get to the valve underneath.

Remove Valve

remove valve RockShox SID BRAIN fork

Use a valve remover tool to remove the valve.

Remove Top Cap

remove top cap RockShox SID BRAIN fork

Remove the top cap using a 24 mm top cap socket. Don’t use a standard socket. A standard socket doesn’t engage the top cap enough and may twist loose when pressure is applied, damaging it in the process.

Remove Internal Retaining Ring

remove internal retaining ring RockShox SID BRAIN fork

Rotate the fork so the stanchions point upwards. The air spring is kept into place with an internal retaining ring. Using retaining ring pliers you can remove this ring.

Remove Air Spring

remove air spring RockShox SID BRAIN fork

Using the lower leg removal tool for some extra leverage, we can now simply pull the air spring out.

Step 7. Remove The Damper Shaft

Remove Compression Adjuster Knob

remove compression adjuster knob RockShox SID BRAIN fork

Rotate the fork in an upwards position again. Using a 2 mm hex tool remove the bolt that keeps the compression adjuster knob in place.

Remove Compression Adjuster, Spring, Bearing, And Ring

remove compression adjuster spring bearing and ring RockShox SID BRAIN fork

Be sure not the loose the little spring and ball.

Remove Top Cap With Damper

remove top cap with compression damper RockShox SID BRAIN fork

Since the crown sits too close to the top cap we can’t use a top cap socket. Use adjustable pliers instead to remove the top cap and damper.

Step 8. Clean Parts

Clean Air Spring

clean air spring RockShox SID BRAIN fork

Wipe the old suspension oil from the air spring using a shop towel.

Clean Stanchions

clean stanchions RockShox SID BRAIN fork

Using a shop towel on a long plastic PVC tube, you can easily clean the stanchions without damaging them. The towel is fixed to the tube so you can move it back and forth without it becoming detached.

Step 9. Replacing O-Rings

replacing o-rings RockShox SID BRAIN fork

Through time and use the o-rings become hard and flat, which causes them to loosen their sealing ability. Because of that we replace each individual o-ring.

You can obviously buy a service kit for your fork, which will include the o-rings necessary. If you don’t have such a service kit and because specifications can be hard to track down for each individual fork, you can always simply measure the cross-section and length of the o-ring using a caliper.

Step 11. Reassembling And Installing The Air Shaft

Reassemble Air Shaft

reassemble air shaft RockShox SID BRAIN fork

Reassemble the air spring shaft, making sure every part sits in the correct place.

Reinstall Air Shaft

reinstall air shaft RockShox SID BRAIN fork

Then insert the air spring shaft into the stanchion. The air spring shaft is also kept into place using an internal retaining ring.

Step 10. Reinstalling The Air Cap

Install Sag O-Ring

install sag o-ring RockShox SID BRAIN fork

Place the sag o-ring onto one of the stanchions and rotate the fork into an upright position.

Reinstall Air Cap

reinstall air cap RockShox SID BRAIN fork

Reinstall the air cap using the 24 mm top cap socket.

Reinstall Valve

reinstall valve RockShox SID BRAIN fork

Insert the valve again.

Step 11. Reinstalling The Damper

Reinstall Damper

reinstall damper RockShox SID BRAIN fork

Insert the damper and tighten it using the adjustable pliers.

Reinstall Compression Adjuster, Spring, Bearing, And Ring

reinstall compression adjuster spring bearing and ring RockShox SID BRAIN fork

Place a little bit of suspension grease in the hole that holds the spring before putting it in with the bearing on top of it. Don’t forget to install the ring as well.

Reinstall Compression Adjuster Knob

reinstall compression adjuster knob RockShox SID BRAIN fork

Reinstall the compression adjuster knob.

Step 12. Replacing Foam Rings And Seals

Pre-Soak Foam Rings

pre-soak foam rings RockShox SID BRAIN fork

Pre-soak the foam rings, which we’re going to install later. Use a plastic container with Öhlins Renep CGLP 68 lower leg oil.

Install Foam Rings

install foam rings RockShox SID BRAIN 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.

Install Fork Seals

install fork seals RockShox SID BRAIN fork

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 seal driver tool we can then proceed to hammer the seals into place.

Step 13. Reinstalling Lower Legs

reinstall lower legs RockShox SID BRAIN 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 14. Inserting Oil Into Lower Legs

Rotate Fork

rotate fork RockShox SID BRAIN fork

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.

Fill Air Spring Side With Lower Leg Oil

fill air spring side with lower leg oil RockShox SID BRAIN fork

Put 10 ml Öhlins Renep CGLP 68 lower leg oil into the lower leg housing the air spring using a syringe.

Fill Damper Side With Lower Leg Oil

fill damper side with lower leg oil RockShox SID BRAIN fork

Proceed to put 10 ml Öhlins Renep CGLP 68 lower leg oil into the lower leg housing the damper as well.

Step 15. Reinstalling Foot Bolt And Rebound Adjuster

Install Crush Washers

install crush washers RockShox SID BRAIN fork

If you haven’t already, remove the old crush washers and replace them with new ones. The last thing you want is for your fork to start leaking because you skipped this step.

Reinstall Air Spring Foot Bolt

reinstall bottom nu or foot bolt RockShox SID BRAIN fork

Reinstall the air spring foot bolt.

Reinstall Rebound Adjuster Bottom Nut

reinstall rebound adjuster bottom nut or foot bolt RockShox SID BRAIN fork

Reinstall the rebound adjuster foot bolt.

Tighten Foot Bolt And Rebound Adjuster

tighten bottom nut or foot bolt and rebound adjuster RockShox SID BRAIN fork

Tighten both bolts using a torque wrench set at 7.4 Nm.

Reinstall Rebound Adjuster Knob

reinstall rebound adjuster knob RockShox SID BRAIN fork

Reinstall the rebound adjuster knob using a 2 mm hex key.

Step 16. Inflate Air Spring

Reinflate Air Spring

reinflate air spring RockShox SID BRAIN fork

Inflate the air spring up to 100 Psi. This is the starting air pressure, which can be modified based on personal preferences and riding style.

Reinstall Air Cap Valve Cover

reinstall air cap valve cover RockShox SID BRAIN fork

Install the air cap valve cover afterwards.

Step 17. Clean Fork

clean fork RockShox SID BRAIN fork

A final cleanup with a bit of Muc-off Bike Protect and your Rockshox SID Brain lower leg service is done.

bio vanseijen

Johan van Seijen

Founder Restoration.bike

Johan van Seijen is the founder of restoration.bike. 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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