Aardwolf

While inspecting the car after my last event I just found the rotor rubbing the inside of the caliper. Has anyone seen this before?



Nothing seems to be broken or lose. The grove is slightly deeper on the bottom of the caliper compared to the top. Both side of the car are the same. The fire path of the pad is aligned good on the rotor.

John Shiels

check rotor dimension? No way to shim it out like a radial setup. Anything bent or hit?

zeusoftexas

check the wheel bearing maybe?

Bill Dearborn

Check the caliper mounting points to the caliper bracket and see if the caliper is loose in the bracket. On my car the dealer tech happened to find the rear caliper bracket was worn and allowing the caliper to move around in the bracket. A new bracket and the caliper stopped moving.

Bill

Jaymz

I second this opinion..

Aardwolf

Back in from the shop. I checked everything and found nothing wrong. I put the wheel back on and pushed to test the bearing and it's all very solid.

I had some bad shudder under braking, I guess this is why!

More ideas?

This is on my C4 with a C5 adapter bracket, that seems fine as the path of the pad on the rotor looks very good. Also the grooves are the same size as the rotor showing the rotor is not wandering side to side which would be a whole mess of grooves. The bottom having more groove then the top is odd.

Aardwolf

Looking at the pad it looks to me like if I moved the caliper up the pads would be at the top most of the rotor where the metal is not supported by the ribs.

The calipers and rotors are fairly new. I put them back together and did not have to force the caliper down onto the rotor. Something must be happening on the track to cause this.

I don't see any marks on the top of the caliper or inside the wheel either.

Aardwolf

If the wheel were to oscillate then there should be marks on the pads from shifting around in the caliper which is stationary. I will pull the wheel and check for that tomorrow. This is very perplexing.

Sidney004

Were the pads radially tapered? Are the dimensions between the piston face and the opposite mounting face parallel?

davidfarmer

rotor mounts to the bearing.....caliper mounts to the spindle. Something connecting the two isn't solid. Did they check the 3 bearing torx bolts????

The backbone of those calipers is ridiculously weak anyway...you sure don't want them to become any weaker!

0Randy@DRM

Guess what, rotors grow during hard braking. You need to ask yourself if this is a new problem on the old setup or did something change. I had a customers car after 25 hard deep brakes, it would rub on the caliper just like yours. Well at that point you have two options, change the bracket design, or cut down your rotors .050 a side. From the picture you have some room for this ninja style cut.

Randy

ghoffman

If you run the numbers, a iron rotor, 13 inch in diameter, will grow .065 inches (diameter, not raduis) per 1000 degrees (F). A 14 inch rotor at 1200 degrees will grow .084! If you need the math, let me know.

Van Steel

If all is good from the previous thoughts you may want to consider...
This is a C5 to C4 brake up grade?
How long has this been rubbing? From the image it appears you may have a 13" rotor verses a 12.8" if this is the case the rotor will on hit the edges of the caliper because of the larger rotor diameter. If you have a 12.8 and this is only happening on one side, the adapter may be machined wrong.
FFT.
PL
Van Steel

Aardwolf

No taper to the pads. I checked the pads after two sessions and I did not noticed the grooves. I drove harder in the afternoon and have some heat checking on the fire path of the pad. There is one crack in the middle that I can catch my nail on but it does not go all the way to the end of the rotor. There was some heat!

The wheel bearing bolts are all solid. I haven't noticed the grooves before this so it just happened in the last sessions of the day.

Is there a 13" and a 12.8" rotor for the C5?

I will take the wheel back off and measure the rotor. I tested the bearing by trying to wobble the wheel and it felt solid.

96CollectorSport

I had the same problem when I put the C5 calipers on my C4, I used the set-up one weekend at Gingerman and went back to the C4 calipers. At least with the C4 caliper you have one mount bracket, with the conversion you have two, I asked around before I bought the brackets if it could handle road racing and they told me yes. Under really hard braking they hit, not sure if it was flex or if it was the rotor expanding but I had more confidence with the stock calipers so I went back to the C4 calipers.

c4cruiser

Where did the rotors come from? Hopefully this isn't a case of getting the Made in China rotors and the dimesions are off. I guess I don't have a warm and fuzzy feeling about the quality of the stuff that is coming out of Chins for things like rotors (or any other auto part for that matter).

Also where did you get the upgrade brackets? There could always be a possibility that one bracket is drilled slightly differently than the other. They are supposed to be mirror images of each other (right and left) so you might want to remove the brackets, hold them together and see if the holes line up.

JaGsC5

Aardwolf

The rotors are from racepages.com and are Centric brand. The adapters are from Jeffvette. I did hold them together when I got them and they were the same. Both sides of the car have the grooves though.

I just measured the rotor, in circumference it is 40.125" which would be 12.77" in diameter. The rotor got a little smaller! Looks like it was a normal 12.8". There is 1/8" of room between the top of the pad and the top of the rotor. I am thinking I will mill down the rotors I have so they are slightly smaller then over winter switch to a better caliper and setup.

Also I inspected around more, there are no scratches, scuffs, or anything else that would show there was movement of parts loose like a bearing.

Sidney004

What pads were you using? It seems like a self correcting problem, two more sessions and your clearance problems will be solved! Can you measure the static clearance between the OD of the rotor and the ID of the caliper housing. I wonder how much compliance the adapter bracket contributes to the problem under heavy force. I am also surprised your boots were not melted off considereing you would need 1000 deg to grow .065 in diameter, maybe the problem was not purely temperature related.
These pictures have turned me off to the C5 upgrade for racing using adapter brackets, I am sure they are fine for the street but the compliance, clearances and basic dimensions may be troublesome for a high heat, high stress application.

Aardwolf

I used Carbotech XP8 with cooling ducts. I am not sure how much more slot will be put into the caliper. I could push the caliper back onto the rotor past where I could get the top bolt in, so there is some clearance there. I had to bump the caliper back up some to get the bolt lined up with the pin. The bottom has a deeper groove though, I could attempt to measure in there.

I tracked down Jeffvette on another forum and asked what he thought, waiting on that.