Question about Brake Piston - rubbed off anodizing - can I still use them?

[Peter B.]

Everyone, I decided to rebuild my brakes. They have SS lined calipers but when I took them apart I noticed that there was some cruddy stuff on the yellow anodized pistons. I cleaned it off but some of the anodizing came off. I ended up with the raw aluminum. Should I re-use these aluminum pistons with new o-rings or should I replace the pistons since the yellow-ish anodizing wore off in places that the brake fluid will make contact with the aluminum?

Thanks in advance for your help

Peter

[Patrick H.]

Re: Question about Brake Piston - rubbed off anodizing - can I still use them?

Replace.

You really don't want to go back in and do it again, do you?



Patrick

[Joe L.]

Re: Question about Brake Piston - rubbed off anodizing - can I still use them?

Replace.

You really don't want to go back in and do it again, do you?



Patrick

Peter and Patrick------


I totally agree. As I have advised before, if ANY of the anodize is worn off in the area of the piston's largest diameter (which is where the anodize is most often worn off), the piston is scrap. Keep in mind that the goldish anodize is not done for decorative purposes. Brake pistons don't need decorative finishes since hardly anyone sees them. I doubt that GM was ever or is now in the habit of ordering finishes for brake pistons for decorative reasons.

By the way, when the anodize is worn off, there will almost always be some aluminum worn off, too. If you check it with a micrometer, I think you'll find this. The piston-to-bore fit is so critical on these pistons that even the smallest amount of wear is unacceptable.

[Peter B.]

Re: Question about Brake Piston - rubbed off anodizing - can I still use them?

Joe and Patrick. Thanks. I can always count on you guys to give it to me straight. I will order new ones today.

As long as I was at it, I was going to replace my brake pads. I am just a weekend driver. Any recommendations?

Thanks again

[Jim T.]

Re: Question about Brake Piston - rubbed off anodizing - can I still use them?

I just replaced some disc brake pads. I used BENDIX D8 Made In America original type disc brake pads and have used them before. I knew what I wanted and called the auto parts stores to see who had them.

[Timothy B.]

Re: Question about Brake Piston - rubbed off anodizing - can I still use them?

I will be corrected about this but with regard to pistons, as long as the sealing surface is not pitted where the rubber seals to the piston inside ledge I was told the pistons can be reused.

A major cause of leakage on these stainless calipers is from cars that sit alot. The piston seals will flat spot from the weight of the pistons and not stay round allowing seepage..

[Domenic T.]

Re: Question about Brake Piston - rubbed off anodizing - can I still use them?

I agree with all that posted but will say this.
I have always seen rubbing on the pistons and have put them together in the past that way without problems.
Another thing is that all the aircraft pistons I have put O-rings on were not anodized. They also use 2 different fluids but one is similar to auto fluid and also removes paint. There is an acceptible amount of wear they allow.
I din't think the brake fluid is the reason for the corrosion. I think it is the moisture that the fluid absorbs and settles to the bottom that starts the corrosion. Brake fluid turns amber when it absorbs moisture, then it's time to bleed and remove it before the two together start the corrosion process.

DOM

[Steve L.]

Re: Question about Brake Piston - rubbed off anodizing - can I still use them?

We anodize aluminum parts in the telcom design office for 3 reasons:

-Keep the aluminum from oxidizing
-Provide a much harder surface for abrasion resistance,
-Keep your hands from turning black when handling the pieces
-It looks a lot pertier


Did I say 3 reasons?