Front Caliper Piston Material

Having an issue with the left front caliper sticking and plan on replacing. Some of the remanufactured units state "metal piston" in the description. Others state that if OEM was phenolic then that is what is used.

What is the stock BMW piston material in the front caliper, metal or phenolic.

This is a 2003 325i.


Thanks

You could google phenolic, which I believe is something like carbon fiber...but we have metal pistons. OE is ATE. I got remanned ATEs and they were fine...but I will say that they rusted. It doesn't bother me at all because I have them powder coated...charcoal gray...from brake dust!

Also, you know that sometimes just the guidepin is hanging up the caliper...it can be cleaned and greased. You can rebuild the caliper, but it's not usually worth it as if you need a piston, by the time you've bought that and the seal kit, you've almost paid for a caliper.

You can also clean up where the pad slides on the caliper...and use brake grease on it too.

...and for my final number...I also had an issue where the pad slipped a little and started rubbing the lip of the rotor...it disappeared in a month on its own.

HTH

Thanks, that's what I needed to know as I haven't had the front apart yet. I did the rears a while back but couldn't remember if the pistons were metal.

I thought about doing some checking as to the cause but in my circumstance where the car is driven by my wife and can't stay off the road long I am just going with a rebuilt and new pads. It was so hot yesterday that when I reached in to feel how hot the rotor was I burned my finger so likely parts are getting cooked by the heat.

Dmax is right that the pistons are metal. However, if you go the rebuild route, realize that you cannot purchase new pistons. Ate doesn't supply them separately from the caliper.

Luke

I ended up ordering a rebuilt Raybestos from Rock Auto. Includes new pins and the anti-rattle clip. It will make the installation quicker and easier

Thanks for the information.