Brembo brake pistons question

[marko]

Shouldn't all 4 pistons come out at the same time after pushing on the brake pedal? I had to pump the pedal and eventually the other two pistons creeped out. (driver side, right is the back/bottom).

[Tervuren]

Once one piston drops and it loses its seal, you keep pushing fluid into air to try to get the others, hence the pumping.

To all come out at once, they would each have to have the same release length, and same friction. When taking apart my single pot calipers, I've found some to be in need of grease, and not as willing to move.

I've yet to do anything with S2 calipers, so I'm afraid I'm not much help.

[rhett]

If the pistons are all moving freely and not sticking, then yes they should all come out at the same time. However, in your photo you have removed the brake pad and so the hydraulic pressure will move out the pistons with the least resistance first. The ones that move later have obviously higher friction - corrosion in bore, sticking seal, etc. Pumping the pedal is necessary to get a greater amount of fluid into the caliper as the pistons are moving to the extent of their travel. It looks like a caliper overhaul is necessary, as ideally you do wnat them all to operate as closely as possible to prevent uneven brake pad and disc wear, as well as under-performance when braking.

[Gawernator]

Rebuild time!

[9FF]

Shouldn't all 4 pistons come out at the same time after pushing on the brake pedal? I had to pump the pedal and eventually the other two pistons creeped out. (driver side, right is the back/bottom).

That's about right, the two bigger bores come out first and quicker than the two smaller bores.

[marko]

I'll check the other calipers tomorrow and see how they look.

[marko]

It's no wonder my brakes have been so crappy lately, only ONE piston even came out on my passenger side. I'm surprised the brakes aren't much worse than they are.

[Gawernator]

Pssh, it's fine. Don't worry about it

[Grandad#3]

Hi Marko, If you are going to replace the Brembo Caliper Seals be prepared to pay around $50.00 each per Seal.

Cheers,
Larry

[marko]

Searching some posts, I found this link Replacement Rotors, Pads, Hardware
which sells a kit with 2 dust boots and 2 pressure seals for $35, but I'm not sure what size to get. I measured 30/34 for the pistons, but I don't think that's right. I saw a lot of posts mentioning 36/40 and the PET is a little confusing for me on the size.