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

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.

Step 1. Clean The Fork

Use Bike Cleaner

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

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

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 the rebound adjuster knob using a 2 mm hex key

Remove Rebound Adjuster Bottom Nut

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

Remove Air Spring Foot Bolt

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

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

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

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

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 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

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

Use a valve remover tool to remove the valve.

Remove Top Cap

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

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

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

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

Be sure not the loose the little spring and ball.

Remove Top Cap With Damper

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

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

Clean Stanchions

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

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

Reinstall Air Shaft

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

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

Reinstall Air Cap

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

Reinstall Valve

Insert the valve again.

Step 11. Reinstalling The Damper

Reinstall Damper

Insert the damper and tighten it using the adjustable pliers.

Reinstall Compression Adjuster, Spring, Bearing, And Ring

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 the compression adjuster knob.

Step 12. Replacing Foam Rings And Seals

Pre-Soak Foam Rings

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

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

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

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

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

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

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

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 the air spring foot bolt.

Reinstall Rebound Adjuster Bottom Nut

Reinstall the rebound adjuster foot bolt.

Tighten Foot Bolt And Rebound Adjuster

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

Reinstall Rebound Adjuster Knob

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

Step 16. Inflate Air Spring

Reinflate Air Spring

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

Install the air cap valve cover afterwards.

Step 17. Clean Fork

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

Johan van Seijen

FoundeR Restoration.bike

Johan van Seijen is the founder of restoration.bike. His passion for cycling in general, and restoring older bikes turned into a website to share his knowledge with a broader audience. Starting out on his father’s road bike and riding classics as the Amstel Gold Race and Liege Bastogne Liege he has shifted his attention to trail, XC, and gravel riding since. No matter how much he loves writing about everything related to cycling, nothing beats actually using his ever-expanding bicycle collection.

Link Facebook-f Linkedin Youtube

You might also like

suspension service

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

Read More »

May 12, 2023

suspension service

How to do a Rockshox Reba lower leg service in 19 easy steps

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

Read More »

May 12, 2023

suspension service

How to do a Rockshox Lyrik lower leg service in 15 easy steps

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

Read More »

May 12, 2023