I am in the process of cleaning/replacing '97 Miata brake items. My issue is the calipers. Upon removing them, they were full of rust chips and the insides were very rusted. I am trying to keep my Miata preparation for the track and autox to a minimum. The calipers worked fine prior to removal.
Should I be worried about the caliper condition with rust inside them?
How should I clean them up?
When you say inside, do you mean inside the caliper bores, or in the area between where the pads go? The calipers are pretty durable. Keith's book has some good stuff on rehabilitating brake calipers.
I'd "gently"(it's a relative term...) sandblast the outside (tape up all the holes!!!) and run a hone in the actual caliper bores. The honing tool is usually available at your favorite retail auto parts store. Buy a caliper rebuild kit to replace the seals and you're golden.
For the rust outside, tapping/striking the surface with a hammer will flake off much of that rust. It will get you a slightly less hideous caliper.
The rust is in the piston cavity. I was concerned that the rust in the piston cavity was an indication of impending failure. The calipers are in working order. I will replace next year if the track days turn out to be as fun as I expect them to be.
Tom: Honing tool for the caliper piston? I have never honed. I looked up the tool and did not understand its use as in this rust case - which is the non-oiled side of the actual piston.
I would be worried about the outside of the piston which is the surface the caliper seals itself on. If you can pump the piston out a 1/2", you can peel back the rubber and inspect the surface. If the surface is rusty/flaking, it is probably gonna be a source of leaks when you replace the pad. The seal is probably still on a clean portion of the piston if it functions.
If you have access to a lathe, you can polish the piston, but the rust might have penetrated the outer chrome coating so any new polishing won't last like a new unit. You might be able to buy a new piston, but a reman caliper would be less hassle if you are not strapped for cash.
Rust inside the piston, it probably is not an issue. The piston walls are pretty thick, it probably won't collapse. You might want to sand the pad end of the piston flat so pressure is more evenly spread.
If you are going on track, I would just spend the $70 on a re-manufactured caliper and not chance it.
I wouldn't be concerned about it. You're looking at surface rust in an exposed, non-criticial area. If the caliper was working fine, there's not much to worry about.
I'd make sure the slider pins aren't corroded. They can be cleaned up with some fine sandpaper if so, and they should be well lubricated. If they're sticky, you'll lose braking power.
Keith wrote:I wouldn't be concerned about it. You're looking at surface rust in an exposed, non-criticial area. If the caliper was working fine, there's not much to worry about.
I'd make sure the slider pins aren't corroded. They can be cleaned up with some fine sandpaper if so, and they should be well lubricated. If they're sticky, you'll lose braking power.
yeah, what he said.
