Topic: Front Brake Caliper

[Bradleyjb]

Recently took my caliper to be sandblasted and powder coated and they blasted the inner portion where the piston sits. Needless to say, I can't get the piston all the way in now. Will the sandblasting cause an issue? Is there any lubricant I can use to get it seated?

[scottly]

With the seal removed, the piston should be free to slide in and out...

[Powderman]

There's no need to blast inside the bore but I doubt it made the hole any smaller. Blasting will remove a minute amount of material so if anything it would make it looser. No part of the piston should touch any part of the housing at any time. Make sure they didn't get any powder on the lips of the bore.

[Garage_guy_chris]

Maybe run a small brake hone down the bore to clean up the blasting? i would think that should clean up the surface.

[Dave Voss]

In my experience, sandblasting aluminum creates many very tiny dimples on the surface, where the edges of the dimples are raised above the original surface, thereby changing the overall dimension just slightly.  So, in the case of an internal bore, the diameter is slightly reduced.  Since the clearance between the caliper bore and the piston is fairly small, it doesn't take much change to create an interference, but a small hone for internal cylinders will knock the edges down to restore the original clearance dimension.

[flybox1]

unless you told them to blast the caliper bore along with everything else....take it back to them to fix it.

[RAFster122s]

I think I would be insisting the buy me a new aftermarket caliper body from DSS and do it right this time when they powdercoat it.

[Powderman]

I think I would be insisting the buy me a new aftermarket caliper body from DSS and do it right this time when they powdercoat it.

I think you would be pissing in the wind for that to happen. I, as a coater, would make you prove to me that the piston fit before you brought it to me and that what I did caused the problem. I would hone or sand the bore lip to see if I could make it work. You would be hard pressed to prove it was the coaters fault.

[LesterPiglet]

Yep, run around the inside with some wetndry and hope that sorts it.
When sending anything out to "others" make sure you deny them all opportunities to f*ck up your months/years of work.

[Bradleyjb]

Ok, I finally got the stuck piston out and removed the inner seal to see, as previously mentioned, that the piston slides in and out of the caliper without the seal just fine. So, it's the seal that's holding it up. Are there any tricks here? It doesn't seem like this should be so difficult...


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[flybox1]

Put a little brake assembly lube, just on the piston seal, and slide it in...

[scottly]

You are installing the piston with the closed end first, right?

[ekpent]

Also make sure the groove that the seal fits in is perfectly clean. A white residue builds up in there that is a major cause of brakes acting sticky. A dremel with a wire brush attachment makes quick work of it.

[Bradleyjb]

You are installing the piston with the closed end first, right?

Haha, yes


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