M caliper rebuild - Pelican Parts PMB SS pistons
 

Hi everyone!

As these things go, I started replacing a leaking fuel pump and have refurbished the front end!!!

I found some corrosion on the side surfaces my M caliper pistons and decided to replace them all with stainless from PP. As I believe is the case for most early pistons the Knock Back Mechanism (KBM) is peened in place unlike very early versions retained by a clip. The new PMB pistons are recessed for a clip but there is no information I could find either Pelican or the caliper rebuild page from PMB showing how to safely remove the KBM.....

What's the best method to remove the KBM from my old pistons? Obviously this is a destructive process and one where I want to not damage the KBM so I won't be cutting the piston in half with a grinder 😂

Appreciate hearing from anyone who has successfully tackled this one and hopefully, help others too!

Cheers
Petehttp://forums.pelicanparts.com/uploa...1728710684.jpg
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http://forums.pelicanparts.com/uploa...1728710800.jpg

Someone else needs to chime in if I’m wrong, but I’d install the new ones without

I'm listening. That mechanism looks to be staked in the piston pretty well.
Might be best removed on a lathe. Chuck the piston, plunge cut at outer edge
to remove the stake areas.
Check everything to insure the old mechanism will work with the new pistons.

So I got it out without damaging it.... different story when the drill broke and *skewered a finger on my left hand 😂... talk about getting my hands dirty!!

anyway.... This was my process:

1. Center punch each of the peened fingers.

2. 3.0 mm pilot drill.

3. 5.0 mm drill - when the chips get bigger you are cutting the washer retained by the peening.

4. I used a small flat screwdriver (shaft through handle) and hammered into the non-peened interface between the washer and the piston.

5. Inverted and hammered from the brake pad side in an anvil to break the washer free ... out it all came.

6. The new pistons did not include circlips so I'll need to see what's available.

Pics didn't load sorry, I'll have try again later.