Brembo PS12 Rear Master Cylinder Dimensions

[Brid Caveney]

We are quantifying sleeving down PS15 master cylinders, to fit the PS12 internals, and need some critical dimensions, if anyone can please help. Need to know actual piston bore size, and bore size where the seal 'pack' crushes (just above the step down to piston bore size) There is a very slight step down, just inboard of the main bore opening (where the actuating lever pivots) then of course the step down for the piston.
Secondly, does anyone have engineering drawings of the 'swaging' tools, for doing the washer crush, on both PS12 & PS15?
Cheers,
Brid.

 

[piranha-bro2]

Can you specify which models the PS12 would have been used on? I have an SF3 rear m/cyl in pieces in the garage and could check for you id it's what you need.

 

[Brid Caveney]

Unfortunately that is also a PS15 cylinder, so no dimensions usable. PS12's were on Laverda 500, plus Ducati 500/600 Pantah (and maybe more?)

 

[Chappo]

My RGS has a PS12 for the rear brake. This is what I have written down:

10.3739.00
25G3    PS12

 

[Gravelroad]

Brembo PS12 is the usual half-incher, read 12.7mm bore. AFAIK the bore is precision honed to at least H6 tolerance, means +0.01mm. Step for the crush ring keeping the piston seal in place should be always the same on Brembos, so you might measure it down on your old PSwhatsoever. Would recommend to get a PS12 rebuild kit firts an then measure the new crush ring, should have a slight press fit. Sleeving out a master is quite a tricky thing, hope you guys know your shit. If all fails, have a look at the breakers for some matching gear, half inch rear brake masters are commonplace on Japanese bikes.

 

[Brid Caveney]

This whole exercise is about keeping the stock cylinder, not just retro fitting any old cylinder, which of course would be relatively easy. An old Japanese cylinder might look a tad out place, on a concourse quality show bike!  I can assure all that - yes, those involved with the project certainly know their 'shit'. As and when we come up with a completed one, we may be offering a 12mm conversion/rebuild service. You send us a (good quality) core, and we convert/renovate same. Just trying to gauge interest in actually having a rear brake? How many folks would be up for having the service done? Too early to be talking costs, but of course we'd be making it fair for all concerned.