Raptord

iTrader: (10)

Update from RB: They are graciously sending me new seals and dust boots for the front. I asked about the seal redesign Penguin mentioned to see if I got those when I bought them the first time or if I had the old design.

Jonno: I don't remember noticing a difference, I got them more as an "insurance" from overheating brake fluid.

killerpenguin21

iTrader: (20)

Jonno - no real change in feel, but I have never had heat issues with them...ever. Which is a nice thing to keep in the back of your mind.

2winscroll

I never had heat issues with the stock Pistons. Most guys who do have removed the heat shields.

2winscroll

Best thing you can do IMO is rip out the antilock BS and use DOT 5 brake fluid.

honda-guy

iTrader: (55)

i'm probably one of the first person to run RB stainless pistons. They used to sponsor me with S2k brakes and i helped them test some stuff. like penquin said, their first set of seals leaked pretty easy, so they fixed it by cutting the seals thicker, nothing else changed. it does reduce leaking (takes couple seasons to start). i think it has to do with rubber compound they use. the stainless pistons are same size as oem aluminum, they have to be so there's no play in the calipers. also stainless has lower thermal expansion than aluminum, not the other way around.

http://www.engineeringtoolbox.com/th...als-d_859.html

the benefits of stainless pistons is lower thermal conductivity from the pad backing plate to the brake fluids. also the RB stainless pistons have vent holes in them to allow air vents inside the pistons. and reduce surface contact with the backing plate.

codgi

iTrader: (22)

What isn't 100% clear to me, is it possible to run their pistons with the OEM seals?

Edit NVM looks like from the other thread OEM seals will work.

2winscroll

Yep pistons are the same O.D.

GTijoejoe

iTrader: (25)

OK, a few things here.

1) the chamfer part of the seal (tallest part) goes towards the disk side of the bore (outside)

2) the seal and the seal groove (shape in the housing) are shaped such that upon releasing brake pressure the seals deform and want to roll back into the groove taking the piston with it to prevent drag. Its a piston retraction feature of the seal, all calipers have it, they can have different shapes.

3) The pistons and seals likely are not identical to the OEM/Brembo parts... tens of microns for instance, hence why you have fluid leaks at cold temps.

4) vented piston caps, phenolic caps, and titanium shims are useful to block or delay thermal transfer to the brake fluid. However, caliper cooling features like air ducts always work best.
If you are looking for the highest quality brake fluid for boiling resistance, Castrol SRF DOT 4 is what you are looking for. If you boil that than you need a real countermeasure to your problem. (Motul 600 or 660 too is good)

Raptord

iTrader: (10)

So, update from me:

Ended up buying two used front calipers to replace my stock ones, because the hard lines going between the two halves of each caliper are completely seized. I wanted to split them to be able to clean and repaint them more easily, and do a better job.

When I got the new-to-me calipers, I swapped in my RB calipers along with the new seals and dust boots they sent me. The new RB seals seemed noticeably thicker than the ones I took out of the new calipers, which I assume are OEM but could also be Girodisc or something else. The new RB seals also did not have a chamfer, at least none that I could notice.

Despite the seemingly thicker seals, the pistons still went in the calipers smoothly. So far I haven't had any leaks, however it's also no longer cold, so I won't know for sure until next winter.

kyoo

iTrader: (29)

i was just swapping out my brake pads and noticed one of the seals I have (RB SS pistons + their high temp dust boots) is leaking. The brakes haven't been through any "cold" cycles, it's been to one track day.

Advice? I don't know how to rebuild calipers, can I do it with the caliper on the car? Or at least still connected to the brake line?

What causes this? Is it possible that I have a different problem? the other 7 pistons are fine.

barneyb

I think SS pistons make more sense in no maintenance average sedans and SUVs then our cars.

Raptord

iTrader: (10)

My best guess would be that you may have accidentally damaged it during install, or maybe you had the same batch as I did and it leaked a bit despite not being in the cold.

The calipers do need to be taken off the car to be rebuilt.

honda-guy

iTrader: (55)

earlier batch of RB piston seals did leak with their stainless pistons, but i think they said they fixed that with new seals. when i first installed RB stainless pistons and seals, they did leak. then i put the used oem seals back on and no leaks. they were on the car till i changed to evo x brakes.

kyoo

iTrader: (29)

yeah these are a recent addition so shouldn't be bad.. hopefully nothing got damaged, someone else built them for me - per above, i guess I'll switch to oem seals, i have ti shims now too anyway and the brakes seem to be managing grea ququi well