Gents,

Happy New Year to all. Best wishes for a safe and prosperous 2022.
Attached is a pic showing some corrosion on the outer edge of each piston bore on a Wilwood 120-9703 caliper. The calipers are a couple of years old. The inner bores are fine. I've spent several beers with either brake cleaner soaked or brake fluid soaked pieces of cloth trying to rub the black **** off, but it is very slow going, and I'm not confident I will be completely successful.
Is this a futile effort--should it be replaced? I've already purchased replacement o-rings and pistons. The pistons look pretty rough. If need be, I can make this a spare.
Thanks,

 

Take this with a grain of salt as I have no direct experience with the Wilwood calipers, but I rebuilt all of the stock calipers on my NB and all 4 of them had some amount of corrosion like this between the Seal / boot lip and outside of the bore. I imagine this is cause by dirt and moister being held between the piston boot and caliper itself.

Seeing as the surface with the corrosion does not interface directly with the piston, I don't see any reason it would cause issues as long as it isn't built up to the point where it's pressing the piston boot into the piston, should work fine. My rebuilt calipers are probably on their 5th or 6th season now and have had no issues.

 

Here's a pic of the pistons. I spent a little time with a professional-type scrubbie and they still look like this. No way I'm reusing these.

 

Thanks for the quick reply. There are no piston boots on these.

 

Pistons are obviously shot.

I have rebuilt calipers looking worse than that with no issues. I'd clean as much of the crud off as possible, and probably lightly sand/scrape the outer edges to remove any burrs or high spots. But the bores themselves look just fine.

 

At $125 each, Wilwood Dynalites are disposable and not worth rebuilding.

--Ian

 

Your caliper bores look fine, the only pressure critical point in the caliper body is the groove for the square cut seal and they look great.
You can remove the damaged in the outer lip of the bore by sanding and the caliper will work fine.
The pistons are TRASH! Along with the groove in the caliper body the surface the square cut seal rides on the piston is the most critical seal surface. It needs to be PERFECT.

This will fix your calipers but...
It will do this crap again.
Wilwood calipers with internal dust shields are available. I believe these are nearly the identical as yours but have the shields
Wilwood Disc Brakes 120-14701 Wilwood DynaPro Dust-Boot Calipers | Summit Racing

SuperMiata has a cool new 11" kit that is really a pretty good deal but it uses calipers without dust shields.

I will use this caliper because of dust shields and RED...
Wilwood Disc Brakes 120-14446-RD Wilwood Forged Dynalite Internal-Dust Seal Calipers | Summit Racing


Sadly, the price of just the 2 calipers gets close to the price of the whole kit from SM...

 

They're Dynapros and the cheapest I've found is $168 in a brief search, but I get your point and was thinking the same thing. However, I already have the replacement pistons and o-rings. I suppose a mid-year tear down and cleaning would have prevented this.
Also, I started trailering the car Aprilish 2021. Mileage will be way down this coming season once the calipers are rebuilt/replaced.
Thanks,

 

11" NA/NB Boxmount can be ordered without calipers

 

****. I found a noticeable ridge inside one of the bores of the other caliper. I just ordered two new calipers and will make the one with the good bores a spare.

Question. Did I cause this by running the friction material down too far?