Wednesday, June 4, 2014

Monarch RT3 Rebuild

   I got a sweet new mountain bike last summer from a guy who ran some kind of training camp. This meant the bike had some miles on it. I had noticed that the rear shock wasn't working like it should, so upon a visit to The Fix, I started the rebuild. The PDF from RockShox helped a lot, as well as this slightly outdated video.
   I needed some specialty tools for this project,  here they are:

All laid out
    • RockShox Monarch RT3 Seal kit - 6 new rubber washers and O-rings
    • 350 psi capable shock pump - for secondary air chamber
    • RockShox air valve adaptor - for secondary air chamber port
    • Parket O-Lube - for seals
    • 7 wt suspension fluid - for the piston
    • 17mm crows foot - to remove the piston form the air chamber
    • 15w 50 oil - for the air chamber
    • Strap wrench - to remove the air chamber
    • Isopropyl alcohol - to clean everything
    • Plastic beaker - to put the 7 wt oil in
    • Valve core removal tool - to pull valve cores from the air chamber and secondary chamber
    • Aluminum soft jaws for vice - to protect the shock from the vice
    • 2mm, 5mm, and 10mm allen key - various applications
    • Grease - for all nuts and bolts
1. Pull the shock off the bike - This was no sweat. I emptied the shock of air from the main canister, and then loosened the 5mm bolts to release the shock. I put a rag around the frame so it wasn't resting on itself.

Shock off

2. Pull the valve from the main air can and nitrogen cylinder - This shock has a second air chamber. Using the core removal tool, pull the valve core out of both the main canister and the nitrogen canister. Now the shock is empty of air. Pull the valve core's out as well.

Core removal tool

Valve core (1 of 2)

3. Remove the main air can - Stick the shock in a vice with some aluminum soft jaws to protect it. Using a strap wrench, loosen the main air canister from the shock body. I had to hit the shock with isopropyl alcohol to get excess grease and dirt off so the strap wrench would have a good grip.

Strap wrench on

   The air can resisted a bit, but with some love it came off.

Pulling the main air can off

4. Remove all seals from the air can - Careful not to damage any part of the shock, I took all the seals from the canister. I labeled where they went just in case.

Seals from main air can

5. Remove the piston head from the damper body - Removing the piston head allowed me access to the oil chamber. This was on really tight and I used the soft jaws again to protect the shock from the vice.

Piston in vice

Piston removed from damper body

   Removing the piston body revealed that the oil level was about 1/4 low, which explained why it was bouncing around so bad.

Damper body and piston head

   Here I went through with the isopropyl alcohol and cleaned everything thoroughly. The alcohol is great because it removes everything, even grease, and evaporates quickly.

6. Replace oil and put piston head back on damper body - Poke the piston head back into the damper body, and measure how far down it goes. Mine was 49.4mm. There is a chart on the RockShox PDF with measurements on it. After it's at the proper depth, replace the oil.

Filling the damper with oil

7. Put piston head back on - Using a crows foot socket and a torque wrench, tighten the piston to 250 inch pounds on the damper.


8. Inflate secondary air chamber to 350 PSI - This required a little adaptor, an a pump that would go that high. Most only go to 300. I didn't have access to nitrogen, so went with regular old garage air.

Inflating secondary air chamber

9. Grease up the seals - Once everything was back together, put the new seals on, and grease them with some Parker O-lube. Everything was squeaky clean and well lubed.

Piston and damper ready to go back into the main air chamber

10. Screw main air chamber back on - Using the strap wrench, screw the main air chamber back onto the piston. Pump it up to 150 and stick it back on the bike.


   The whole process took a little under an hour, and was pretty enjoyable really. The shock performance is noticeably better! It made me wish I'd done this last season. 

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