How to guide for brake booster/ master cylinder upgrade on a Sirion M1.
I did this upgrade after installing Copen front brakes and Applause rear brakes on my Sirion. I found the standard 3/4” (19mm) master cylinder just wasn’t moving enough fluid and I had too much travel in the pedal. After a bit of research I found the M3 Sirion booster/MC assembly could fit. It has a 13/16” (20.6mm) bore and the booster is also larger providing more assistance. I did this conversion on a LHD Sirion, I am not sure if it will also work on the RHD Sirion. If you try it please share your results
- M3 brake booster (part # 131010-15210)
With alu spacer block!
- M3 master cylinder (part # 47201-B1020)
- Remove brake booster and master cylinder
- A small section of the firewall needs to be cut out (or hammered in )
- Shorten the threaded rod from the brake booster by 1cm to prevent fouling on the brake pedal. Fit the fork from the original brake booster.
- Install the new brake booster and master cylinder. The brake lines can be slightly bent and moved to fit the master cylinder with minimal effort.
- Fabricate a mounting bracket for the reservoir. In my situation I had to extend the hose between the reservoir and master cylinder due to the location of my strut brace. I welded a small bracket to the charcoal canister mount for the reservoir.
- The pedal free-play will need to be adjusted and the brake system will need to be bled. Refer to workshop manual.