Caliper Piston Material Q?

[ChriswithaC]

I was wondering if you guys could offer some input into selecting a material for some replacement caliper pistons.


A friend of mine were doing some work on his car and ended up having to pull the brakes off. When we took the brakes off we noticed that one of the pistons was missing a large chunk from the top on a caliper that looked like it had been severely heat-soaked by the previous owner on a track day.


Long story short, the Porsche calipers made my Brembo are apparently "non-serviceable" for some reason.......even through the pistons look identical to many of the replacement pistons I've been able to find for Brembo's. However, I have only been able to source 30mm pistons out of the 30/34/38mm pistons required on each side of the calipers.


So I'm going to take some measurements and put together some drawings for a machines shop to make a new set of pistons. Could you guys recommend a suitable material for this application? I was thinking some 1045 cold finished bar but don't know if I want to have them corrode. The other options are stainless which is hard to machine and has a high thermal expansion rate.......or aluminum which is easy to machine but may have to be hard anodized to take the abuse in such an application.

If you guys could off suggestions for a material and grade I would really appreciate it.

 

[swall]

Standard practice in the U.S. for metal caliper pistons is SAE 1006-1008 steel, cold extruded then finish machined on the O.D. Chrome plating is applied for corrosion and wear resistance. Fully machined stainless, such as 17-4, would be a good way to make a one off functional part(or piston set)without the expense of plating.

 

[thruthefence]

I think there's a some folks making Girling stainless steel replacement pistons for a bunch of old Brit sportscars. Maybe you could track one of them down?

They make them from stainless so they don't corrode in place while the Spit or Europa is Brokedown & out of service for some other reason

 

[tbuelna]

ChriswithaC,

If you can afford it, the best option is titanium. It has a low thermal conductivity, which limits heat transfer from the pads to the fluid. 6Al-4V titanium bar is a good alloy. It can be PVD coated with .0002 inch of titanium nitride to give a hard wear surface.

If cost is an issue, try 4140 alloy steel bar, heat treated to Rc 38-42, finish machined, plated with .0002" thin dense chrome (for corrosion resistance, hardness, and low friction), and lightly finish ground to 16 microinch on the OD.

If you can afford a Porsche with Brembo brakes, making your own caliper pistons should not be cost prohibitive for you.

 

[ChriswithaC]

Thanks for all of the replies guys. Really appreciate it.

I ended up finding some StopTech pistons that looked nearly identical so I suggest my friend give them a shot. When they finally arrived I measured them up and compared them to the existing pistons. They were nearly identical and all the critical surfaces were spot on.


Just because you have Porsche brakes.....it doesn't mean you drive a Porsche or that mondey is no object. lol