Hey guys,

I have a Wilwood 11.75" race kit on my car and everything was working fine on the street and my previous two track days. However, on my last track day, when I was changing out my track pads to the BP-10 for the street, I noticed scrape marks where on the caliper. It looks like the rotor was hitting the back of the caliper bridge, but I didn't hear it on the track or feel anything.

Here's a pic of where it is hitting:


Does anyone know what would cause this all of a sudden? Maybe one of my bolts is loose? I can't move the caliper or rotor with my hands, so it doesn't feel loose, but maybe only under hard braking does this occur.

Hopefully someone can chime in.

Cheers,
Steve

 

is it like one distinct scrape mark? cause it could be a rock getting caught..

cause if u say the rotor is hitting the caliper, then maybe a re-installation of the caliper will do the job..

did u hit up the UBC track day?

 

A rock or other track debris was my first guess also.......is this on the leading edge of the caliper?

 

I suspect you have a loose bolt. Try prying the caliper with a screwdriver/prybar to see if it will move. I know my wilwood 13" rotor is very close to the caliper and I always worry that it will rub. When I tighten the bolts I try to give as much clearance as possible but I do not have much play at the bolts.

 

Yes it was. I thought it was debris as well, since it didn't happen until my 3rd track day, but the marks were indicative of a rotor striking it (two marks where the edge of the rotor is and none in the middle where the rotor vents are). Even though the caliper doesn't seem to be moving when I checked it yesterday, I will still tighten the caliper bolts this weekend and see if it happens again.

 

In the directions

http://www.wilwood.com/pdf/ds492.pdf

it is referenced you install one shim (#14) between the bracket and caliper for initial test fit. Additional shims are supplied for use as needed.


How many are you using?

 

Hi Todd,

I had my shop install them as I was away that weekend for a hockey tournament. I'm taking them in the car on Monday for them to take a look. It looks like there in one shim on both the calipers.

Thanks,
Steve

 

I got the impression from the Dinan604's figure that the rotor is hitting the caliper at the top of the rotor (vane area) not the side, so the shims would have no affect on the hitting location.
Dinan604,
Did you resolve the problem? What was the cause?

 

Yes, quikmni, you are correct. I have the correct amount of shims for the caliper mounts. The installers who did my brake kit didn't put in the safety wire on the bolts that connect the rotor to the hat, so due to the extreme heat at my last track day, the rotor bolts started to back out and the rotor was ever so slightly loose. That caused the rotor to crash into the caliper. I have tightened them back down for now as for street use, they are fine. However when I get the car on the lift this weekend, I will take them off, apply loctite on the rotor hat bolts and install the safety wire.

Luckily there was just cosmetic damage to the caliper and I noticed this soon enough. I tore my installers a new one as they skipped over certain parts of the install instructions and put me and my car at risk.

 

I don't know about using loc-tite on them. With proper torque and safety wire (and occational checks), you should be fine.

Matt

 

Actually both are correct. Shims on the radial stud (and the thick spacer I hope they gave you back) are used to establish the bridge clearance. The data in the pdf calls out usually for 1-2 shims per stud (plus spacer for 12.2) and a clearance check for air gap as necessary.

Lose hat bolts however in this case would clearly cause the rotor to shift on them and make light contact. I'd be concerned at this point about the potential for damage to both the hat and bolts. Properly torqued to 14lbs and wired they should not be lose. I'd look for any out of round damages to the leading thread area of the hat and suggest you replace the hat bolts with new parts. They are considered a torque to yield bolt and should not be reused- especially given the potential rocking nature they may have seen.

Red loctite to the hat is fine, but....keep in mind that removal later could damage the threads in the alum. I have no problems with using it but I'd urge you to heat the head with a torch before removing them in the future.

 

Hmm, really? The Stoptech BBK I had on the Audi before required loctite...but then again no safety wire. I will just use safety wire then.

 

Hi Todd,

Thanks for the help. I can just get new hat bolts from any hardware store or should I order a set through you? I'm currently using one shim on the caliper studs and I have ample clearance to the rotor.

I would like to say that these brakes with the Poly B compounds are incredible on the track and the other Mini drivers on the track were quite envious of my ability to late brake and not suffer any brake fade throughout the day.

Thanks a ton Todd!
Steve

 

FWIW, you have to watch bolt grade when you go to HW stores, and I haven't seen any that have the bolts drilled for safety wire....

Matt

 

Unlikely to find drilled rotors at HD or ACE. McMaster or such on line but the kit with washers from me is only $13. I wouldn't open the drill index for $13...

 

Thanks Todd, payment sent. I did manage to find them locally (out-of-stock however) at our local aircraft/auto fastener store, but they were $1.36 each and I had to wait 2-3 weeks. It's good to know that I have a place just around the corner to get these...just in case.