Brake rotor scraping caliper
 

Here's a weird one. No issues with clearance under normal conditions, but at some point during braking the outer part of the disc is making contact with the rear part of the caliper. This is happening on both front brakes in the exact same way. I'm thinking maybe the caliper or caliper bracket is flexing when the pads clamp.

Any ideas on a fix? These are Wilwood D52 calipers.

https://forums.maxperformanceinc.com...1&d=1709697332

https://forums.maxperformanceinc.com...1&d=1709697339

Is this a rear-disc conversion?

Set up a magnetic dial indicator to see if the front plate of each rotor is taller then the rear plate.
If not then your caliper’s are at fault which could be for a few reasons in terms of machining work.

Do some grinding for clearance and let it ride.

Anything that could allow the brake rotor to move independently of the brake caliper needs to be checked.

That would include things like worn out bearings, spindles that are flexing, loose bolts holding the caliper brackets etc.

As Scarebird points out, it's possible the rotor is too large for the calipers. In general that caliper is designed around the factory 11" rotor. It can go on a 12" rotor, but you need the proper mount to position it correctly in that case.

If the brackets have wallowed out their mounting holes, this could also cause an issue, especially under braking.

Wilwood shows two different D52 calipers, one for big car/pick ups primarily, the other for all other cars. I didn’t realize that, I just figured one caliper fit all….is it possible that you have the incorrect calipers? Is there a part number stamped on them anywhere?

11291 for A/F etc cars, 11290 for B/trucks etc.

The two calipers listed here are structurally the same size. One version has 1.25" dual pistons and the other uses 2" dual pistons.

If you are using these as replacements for the stock caliper with a 2.75" or 2.94" single piston, you want the larger dual piston version from Wilwood.

They all use the same 7.06" floating mount though.

It's possible there is a machining issue with the calipers, but I suspect it's related to the rotor or mounts in this case.

These calipers are probably 8 or so years old. The OD on the pistons are 1.983, so I assume it's the 2" version.

Not sure how long this has been an issue - I assume since the get go. I had everything apart when I rebuilt the suspension last year, but didn't change or replace any of the parts. I didn't notice the problem then, but I wasn't looking too close. The backing plates and caliper brackets are stock reproductions the spindle is factory. I'll check to see if there's any slop in the caliper brackets.

I'll get a diameter on the rotor. I sent them off with my son to have them turned at his school auto shop today.

Following up - the rotors measure exactly 11" in diameter.

I did notice the bolts for the caliper bracket could have been a little tighter, but there's no obvious play with the bracket even when I loosened the bolt. The caliper to rotor clearance is definitely greater on the top than it is on the bottom, but there's clearance. Guess I'll button it back up and see how it goes.

I’m pretty sure the factory 11” rotors are actually 10.95” so perhaps that may be a factor.

Interesting. I measured them with a metal ruler vs. a caliper or mic so I could be off.

I ended up doing a little bit of clearancing on the caliper in the trouble spots before I put things back together just to give a little extra room.

There is a slight variance between brands on rotor OD but not enough to cause an issue with any of my iron D52s.
Like others said check for something allowing too much movement in the rotor(bearings) or caliper bolts, O ring guides in the caliper not worn out or hard

How are those brackets and hardware looking? Photos?

Are your pads worn some? Could be the caliper flexing as the pads wear and the pistons come out of the bores more. If everything is tight and there are no cracks or anything on the brackets then adding some clearance to the calipers/rotors as others have said would be the way to go.

First Guess: THERE IS SOMETHING WRONG. My money is on the aftermarket caliper mounting brackets if not just plain ol' loose fasteners. Mis-adjusted wheel bearings, perhaps.

Carving more "clearance" into the caliper is crazy. If the caliper doesn't fit, find out why.

Pads are brand new. Bearings are new. There's no play in the rotor.

My guess is that the bottom caliper bracket bolt wasn't tight enough. I was able to tighten it up another 1/2 turn or so on both sides. Looking at older pics from when I rebuilt the front end, the outside edge of the rotor wasn't worn, so this started happening after I put things back together last year.