Why Stainless Caliper Pistons?

[jamesjedi]

I believe the factory did not use stainless caliper Pistons, why should we?

Stainless is still a disimilar metal to iron, as is aluminum. The factory used - EDIT; NOT chrome plated steel but polished steel. If the fluid is replaced annually, would this not remove any corrosion issues?

Unless there are issues with the quality of the after market piston?

[Bill Verburg]

Originally Posted by jamesjedi

I believe the factory did not use stainless caliper Pistons, why should we?

Stainless is still a disimilar metal to iron, as is aluminum. The factory used aluminum. If the fluid is replaced annually, would this not remove any corrosion issues?

Unless there are issues with the quality of the after market piston?

ss is a poor conductor of heat relative to aluminum, high end race calipers use Ti and Ceramic in caliper pistons, other designs vent them.

[Drisump]

I'm assuming they are offered because if you have taken apart old calipers... At least on my 3.2, the OEM ATE calipers and pistons are iron and develop quite a layer of rust outside the piston seal. I'm assuming that the SS piston is supposed to minimize the possibility of corrosion binding between the cylinder and piston. The question of disimilar metals is a logical concern. BTW I had done brake flushes every two years as per Porsche's maintenance schedule but the corrosion occurs where there is no fluid. Cheers

[pampadori]

I'm noticing more and more people offering phenolic pistons which are probably even better.
A quote from one of the larger brake caliper rebuilders in the world:

Q. Are steel pistons better than phenolic, which are plastic?
A. Phenolic pistons have an advantage over steel pistons;

Phenolic pistons do not rust
Phenolic pistons maintain original size regardless of age. They are not affected by heat or moisture in the brake system
Phenolic pistons do not transfer heat to the brake fluid
Phenolic pistons are lighter than steel
Phenolic pistons are fuel efficient and noise dampening

[Liam O]

Sounds like three cheers for Phenolic pistons

[ganun]

Was it Ford with phenolic pistons years ago....the warp and get stuck in the bore, I was there

[jamesjedi]

The cost of stainless is very similar to the cost of local custom steel versions that are chrome plated.

Interesting to see that yours rusted with regular flushes.

My pistons don't look that bad, but my calipers look amazing. They have been sand blasted and are now getting plated. Perhaps I will "splurge" for the stainless pistons.

[DRACO A5OG]

Just make sure they do not look like these. They leak, ask me how I know.



Only one was okay, replaced them all

[jamesjedi]

Those are OEM? What did you replace them with?

[KTL]

The original pistons aren't chrome plated. They're plain uncoated steel that is nicely machined/polished. The corrosion tends to occur when the plating on the iron calipers degrades and allows the rust to start in the bore area beyond the pressure seals. Pistons that are exposed beyond the pressure seals will also rust underneath the dust boots, especially when the boots are damaged (obvious)

Ceramic pieces are good but they're not infallible. Check out some BMW applications and you'll see some of their ceramic inserts crumbling. I've seen this happen on the 1-series caliper pistons.

Simple stainless pistons are a nice way to go. Check out the NLA Porsche/Stodard site and they sell 48mm stainless pistons for the SC & Carrera A calipers. I think this is a really nice upgrade to do for track duty with the stock brakes on these cars.

[DRACO A5OG]

Originally Posted by jamesjedi

Those are OEM? What did you replace them with?

Yes, as far as I know. They are rears so I just got the Centric brand, they seem to be perfectly fine for my use which is mostly if not all street now a days. If I was DE'ing would definitely go with something more robust.

[jamesjedi]

I semi edited my first post to not misrepresent the piston material.

I see that they are priced individually. That would be roughly $400 for all four calipers. They have some interesting products at Stodard.

[KTL]

Yep it's just under $100 per caliper to install the stainless pistons. The alternative is what though? Sure we can buy reman or new calipers but those come with steel pistons.

Nice thing about stainless is the reduced heat transfer like Bill said. Or get some air ducted to the brakes. A much more expensive brake swap to something like 930 or 993 or VCI brake setup is way more expensive and those all have anodized aluminum pistons, which is odd IMO, but they also have aluminum caliper bodies which shed heat better. So $100 per caliper is a lot cheaper and the improvement with stainless is pretty substantial when you look at the thermal properties of stainless vs. others. Link below courtesy of 911pcars/Sherwood Lee here on the forums.

Seine Systems > Ti Brake Shield

Unfortunately STodard only offers 38mm rear pistons in stainless. So those people with Carrera rear calipers that use 42mm pistons can't install the stainless.

[vintagecarlover]

I need 8 38mm Pistons for 930 calipers. Ideas that won't break the bank?

[DRACO A5OG]

38MM really? wow those are small, my rears were 48MM.

[winders]

Does anyone know of a source for stainless pistons for 930 rear calipers?

[RSTarga]

PMB - DIY Caliper Parts
They have others too.
anodized aluminum

[DRACO A5OG]

Oh nice, time to get some new front caliper pistons

[jamesjedi]

Paragon may have some 930 pistons. The front calipers for the 930 pistons are all 38mm. The rear pistons are 30mm.

[manbridge 74]

I'm going to rebuild some S calipers with aluminum pistons. Motorcycles have had these for a long time. I will be using some air diverters for cooling. I'll report any over heating.