C5Lion

Last week I posted about a problem I noticed after changing brake rotors from an old set of DBA4000 rotors to a new set. For background info take a quick look at the following post but once I changed rotors I noticed one of the OD pins that holds the pads in place would touch the rotor when I had the wheels turned to the right all the way. Per feedback in the following post, I was told this is not to uncommon and go ahead and file the pins down. That did solve the rub problem.

I have a 2007 Z06 with stock calipers.

http://forums.corvetteforum.com/auto...lem-c6z06.html

In any case, this weekend I went to Autoclub Speedway in California and on the 5th lap had a major rotor failure. I was really lucky it happened at a place where I could continue straight and not hit anything. This braking zone is ~130 to 30 mph. The rotor totally separated from the inner hub of the rotor as shown in the picture. It happened after the car slowed down to ~ 60 mph and then snapped.



The following is a summary of what I have learned since about my rotors/calipers.

1. The rotors sit inside of the front calipers on both sides of the car much closer to the OD of the caliper. In other words, the rotors are not centered in the middle of the caliper. See the pictures.
2. I was fortunate at the track to not seem to have damaged the car so I replaced the rotor with an OEM one that my buddy brought. It had been on his car at 1 time and he had no problems. This rotor was installed and when I went our for a test drive in the parking lot, a OD pin on the caliper was rubbing the rotor under light braking.
3. Everyone that looked at this issue, did not understand what was going on. We decided to shim the caliper toward the OD of the car to see if we could get the pins away from the rotor. We installed a ~0.100" washer. This seemed to fix my pin rubbing problem.
4. I then went on the track for a few laps to see if everything seemed OK, but now noticed what sounded like a scraping noise on this wheel when turning aggressively to the left. I run Hoosier R6 tires by the way. My initial thought was it was a pin, but now I am not sure since the pin should have been far away from the rotor. Wheel bearing?
5. Hindsight being what it is, I did noticed what sounded like a pad grinding noise on the laps just prior to the rotor failure. At the time I thought it just was the pads bedding to the new rotors. I did season the rotors for about a week prior to the track event.
6. After the rotor change I think I also noticed the same type of noise and feel that I mentioned above so I decided to not push the issue any further until I can figure out what is wrong.
7. I checked the rotor offset between my old 2 DBA rotors, my one still good new DBA rotor and an OEM rotor and they all seem to be within 0.010" of each other. This is the distance from the face that mounts to the hub to the outside face of the rotor.
8. All the DBA rotors listed in item 7 were all within 0.010" or so in overall thickness of the actual rotor surface except the OEM rotor which was ~ 0.030" less in overall thickness.
   

So the question now is, what is wrong? Questions I have.

1. Why are my rotors not in the center of the caliper?
2. Why did I have to file down the pins a few thousandths when I first did change my rotors.
3. Has my car always been this way with the spacing of the rotors and calipers? I just don't know. I assume the design intent is for the rotors to be in the center of the caliper.
4. Do I have a wheel bearing problem? I have run about 12 events on Hoosier tires and 7 or so more on street tires over the past 3 1/2 years. I don't feel anything unusual with the bearings or ride.
5. Did I have a rotor defect that caused my problem? One of the guys that looked at my cracked rotor thought maybe I did, I am not exactly sure.
6. Did I damage something when the caliper broke that now caused problems with the OEM rotor and caliper? If so, there is nothing obvious to me when I look.

Has anyone else seen anything like this?
What should I try or measure next?

PS..... I can't get the damn supposedly good DBA rotor off the car. I am bringing home a big sledge hammer from work to see if that will work.

longdaddy

the most simple explanation would be either incorrectly mounted hub (has it ever been off the car?) or play in the hub/bearing. the fact that you have noise while turning would support this theory.

next on my list would be twisted/deformed caliper. i wouldn't put that past PBR.

what's with the dark stuff coming out of the bleeder screws? that does not look right

Sidney004

Can you get closer, sharper pictures of the rotor(s) at the fracture point front and back?

Dirty Howie

Leo

Are you saying your passenger side front rotor needs to be hammered off?? Why would it not just slip off after removing the caliper.

Do you remove the pins to change pads, or just remove the caliper?


DH

C5Lion

Hub has never been off the car. How do I test or measure if I have a bearing issue?

My caliper looks to be fine and has been for at least 20 track events.

I noticed that dark stuff too. Wasn't there before the event. Have not really focused on that but will look into.

C5Lion

I will try tomorrow.

dvandentop

wow very crazy, glad you are, cant say i have seen a rotor do that

C5Lion

Yes, I just got it off. I needed to use a little bigger hammer and it came off. Not sure why it did come off easier. I have had to bang them before but to this extent.

I have never removed the pins. I always take off the caliper.

Dirty Howie

Is it possible your hub is slightly bent or out of round??

The soon as I take my caliper off the rotor wobbles loose by itself .... no force at all. So seems to me either the rotors main hole is out of round or the hub has to be.


DH

longdaddy

the best thing I can think of is find a friend with a C6 corvette that has never been tracked, take his front wheel, caliper and brake rotor off and rotate his hub by hand, then do the same to yours. if there is significant difference in smoothness/binding, yours is going.

you could also check the torque on the hub bolts but if it has never been off the car I am 99% certain that is not the problem.

with repeated heating/cooling the caliper may have developed a "bend" in the plane perpendicular to the bolts, but without some precise measurement equipment and/or brand new caliper to compare to, I am not sure how to detect that.

redtopz

It defintely looks like your OD pin was still grinding on your rotor. I wonder if the C6Z hubs are stronger than the C5 hubs. I've gone through a bunch of hubs in the past 2 years and now I'm installing race hubs. There are 4 things I would do to prevent that problem from repeating:

1. Check the hubs and make sure they are all good. Any signs of pad knockback or if your wheels wobble untrue at all are signs of bad hubs.

2. Stop using DBA rotors if they have questionable fitment with your calipers. Try stoptech or another brand that have been proven with the C6Z's.

3. Maybe remove the padlets and install monoblock pads. I think they are probably a better setup for track duty. Otherwise grind down that OD pin as much as possible.

4. Check the front calipers. Are the pads wearing evenly? You might be better off upgrading to better calipers since you are pretty serious about tracking the car and are a very good driver pushing the car to it's limits.

longdaddy

i guess the last possibility is deformed upright but it is stronger than the other two (hub/caliper) so it would be the one least likely to change shape. anything is possible at this point though - you have something clearly damaged and my money is on one of these 3.

if I had to make a blind guess, I would say calipers, just because PBR branded parts have no business anywhere near the racetrack

EDIT: i would disagree with the advice of just grinding the pins and trying different rotors. you have established that your calipers are off center with different types of rotors, so DBAs are clearly not the problem and pin contact is a symptom, not a cause.
in addition, the way in which the rotors failed only supports this. this is NOT how the rotors fail from excessive heat/wear and you are right to be scared. find the root cause before going back to the track.

redtopz

That's true. I need to add a #4 to my post above.

Z11409

Start with the basics--measure everything.(twice)
Need a dial indicator to measure runout of the hub.
With rotors removed,spin the hub and check for play (bearing) and runout,Make sure hub does not wobble.
Check that the rotors lay flush against hums
All our DBA rotors where not centered to rotor faces.
Compare OEM rotors to DBA. Make sure rotor does not bind on wheel studs. A auto machine shop with a brake lathe or a surface grinding machine can also be used to compare.
I have checked the the depth of threaded pin holes and they where very close to being all the same.

longdaddy

i had the rotor get stuck to the hub after really hard use so I had to resort to using one of those no-bounce hammers to loosen it, it was fine afterwards. from OP's pictures and experiences, I think he is running his car pretty hard so this may not be a big deal, at least compared to his other issues

longdaddy

on a lighter note, at least you upgraded from DBA 4000 to 5000 for free...

Dirty Howie

I was at the track with him and have been many times. He is very fast so he does use his brakes.

I really have no mechanical knowledge. I was just mentioning what seemed very unusual to me. It sill doesn't make sense. How does a couple of track sessions cause a new rotor to need to be hammered off??


DH

C5Lion

I am going to check if the hub if it has runout. To the eye it looks Ok. I will use a dial indicator and see.

longdaddy

if it's just couple of sessions, yeah that would be odd. my stuck rotor experience was after having same pair of rotors on for 2 DEs (~10 30 minute sessions) on a track that's pretty hard on the brakes with hoosiers on

C5Lion

I don't see how the pins could have been grinding after I added the spacer to the caliper. I moved it 0.100", but something was still making noise. I also did not see pin markings on the rotor.

When you say hubs, do you mean the wheel bearing hubs? What symptom did you have when you knew it was time to replace them?

I don't think I have experience pad knockback because the pedal usually feels good and does not require more pedal travel. How much more would you have to push the brake pedal when this happens?

My pads do not wear that even, but this is common with C6Z calipers. I would call the wear I see on my pads pretty normal.