I've heard of this problem before here on the forum, but yesterday it was my turn to experience it!!!

I was at Daytona for a 3 day HPDE running the Rolex 24 course in my 2006 Z06. We were running 4 thirty minute sessions each day. The track is VERY hard on tires, and the brakes get a good workout coming down from pretty high speed on the straights.

I ran hard all Friday and Saturday, so I was keeping an especially close watch on tires, brake pads, and rotors - well, everything.

On my 2nd session Sunday morning I had been out about 20 minutes. I came out of NASCAR Turn 4 and was continuing to accelerate down the front straight of the tri-oval at about 165. I had just passed another car and was still accelerating when I heard a loud "bang" - it sounded like it came from the rear of the car (but turned out to be from the front).

I was still several hundred yards from the s/f line and brake zone for the turn into the infield, but I lifted off the accelerator and started to decelerate. I was initially concerned about a tire problem, but the car was going straight with no vibes.

I usually enter the brake zone at about 165 to 175 mph, depending on traffic, but I had slowed to about 150 when I applied the brakes. The steering wheel pulled hard to the left, so I immediately let off the brakes and blew the turn. You're coming down the front straight, so the runoff if you blow the turn-in is to just steer between some cones and continue down the track, and that's what I did. I slowed down, turned around, and continued all the way around the course slowly so I didn't have to use the brakes much. When I got back to the paddock area this is what I saw:




That's the front right caliper and you can see that the bottom pad pin bolt had backed out, and that allowed the bottom padlet to fall out of the caliper!!!

I had been watching everything very closely, but was mostly keeping a visual watch on those bolts (and feeling around behind the caliper to check that the inside ones weren't backing out). At least twice I had taken a 6mm allen wrench and checked them to make sure they were tight (later model years require a torx bit to tighten the bolts).

With the padlet gone, when I applied the brakes the piston was pushed against the rotor and caused this:




You can see it's scored where the piston scraped on it, but it actually isn't damaged too badly and I'll keep it as a backup. It's got a lot of spider cracks, so it's got a very limited life remaining anyway. The piston that contacted the rotor got ground down a little bit, but it was still okay to use for the next 2 sessions.

Over lunch I took off the caliper, pushed the damaged piston back in, and determined that it would work okay for the next 2 sessions on the track.

I put on a backup rotor on the right front, fresh padlets for both front calipers, bled the 2 front calipers, and was good to go for the afternoon sessions and the brakes worked great.

There was a very small nick on a spoke inside of the wheel - I'm not even sure it's from the pad pin bolt, but if the bolt does back out far enough it could cause damage to the wheel. There was a strip of wheel weights that had a big gash in them from when the padlet hit them when it came out of the caliper.

Now I've got a project - I'll have to get a bunch of pistons and seals/gaskets and rebuild the calipers before my next track events - I probably will send them out to MikeThePowdercoater because they're pretty ratty looking.

When swapping pads I always just remove the caliper, so I haven't regularly removed/replaced those bolts, and I did check them with an allen wrench the previous afternoon and they looked like they were seated properly when I checked them visually.

Moral of the story - if you have stock Z06/GS brake calipers, check those pad pin bolts from time to time. You don't want them to back out and allow a padlet to fall out.

If you run one-piece pads you probably won't have that problem - if a pad pin bolt backs out, the crossbar on the caliper will keep it from falling out, especially if your one-piece pads have holes in the center for the center pins to go through.

So.....keep an eye on those bolts!!!!

Bob

 

The one that came out my car earlier this year was the one above the one on your car. I had one piece pads so didn't lose the pad but the bolt did gouge the back of the spokes on my LG World Challenge wheel. Luckily, I was able to get it to a wheel repair expert and have it fixed.

My bolts were frozen in place when I checked them a couple of days before when prepping the car for the event.

Bill

 

may i ask what the traqmate setup that you use costs

is it easy to customize the instrument cluster ?

 

Sorry to hear about that.
I'll keep an eye on mine from now on. Theres only about 2-3mm clearance between my calipers and back of the CCW's.

 

Bob, glad you are OK, that could have gone a lot worse. 2:12 is moving along!

Are you going to switch to 1-piece pads now? I will definitely add Daytona to the calendar for next year.

 

That happened to Pfadt's vette as well.

I would guess that due to the heat, red loctite wouldn't hold it, I don't know for sure.

Since you pull the calipers to replace the pads, is it possible to cut a groove in the pin, on the pad side, and put a circlip in place to keep the pin from coming out?

 

Traqmate is a great datalogger!! Take a look at their site for info on pricing and all the features available:

http://store.traqmate.com


With the Traqmate, you can log a whole bunch of different parameters - RPM, speed, G's, fluid pressures/temps, steering angle, suspension deflection, and just about anything else. Butt....you have to tap into the car's sensors or add your own.

There are a bunch of new data acquisition devices coming out that hook into the OBD II port.

And, there are also some very good apps for smartphones - the premier one is probably "Harry's LapTimer". I know it works on an iPhone, but what other devices are supported, I dunno:

http://www.gps-laptimer.de


With the Traqmate, I use their TraqStudio software to put that "dashboard" thingy on the video, and you can change colors and opacity, but I don't know what kind of cusomizing you're interested in.

If you have a different datalogger, there's a software called TrackVision:

http://www.trackvision.net


TrackVision may be more customizable, and it works with numerous different dataloggers, including Harry's LapTimer. You can see a list on the site above.

Do a search for "data" or "datalogger" in the AutoX/Roadrace section of the forum and you'll find a huge amount of info and guidance. Here's just one such thread:

http://forums.corvetteforum.com/auto...-software.html

Reviewing your track day can really lets you know what you were doing out there, and it can really help you drive the track better by analysing your braking, turn-in, apex point, etc., etc., etc. You can compare laps and see what worked best so you can improve your driving.

If you just want to video some mountain driving and add some data, you can start out cheap with a smartphone app and a GoPro.

Good luck finding something that will help you enjoy your Corvette driving experience even more!!!!

Bob

 

Yeah, I'm not quite sure what I'm going to do.

I checked the Loctite site and they say red is good for up to 500*F, but I know the rotors are getting hotter than that (the DBA rotors have heat paint stripes on them). How hot the caliper is actually gettin, I dunno.

I do have a set of these Racing Brake pad pin bolts



and I'm going to install them, but I don't guess they'll be any better than the stock ones - their primary advantage is that they're easier to remove with that 10mm hex head. I guess maybe I could torque them down better as well.

All the wisdom in the AutoX/Roadrace section is that a car that sees the track regularly should probably just have some aftermarket calipers, and that's something I'm definitely considering!!

Bob

 

I have been thinking of using metal faced duct tape over the bolt heads just like I tape the wheel weights. Caliper temp isn't getting over 570 degrees or my brake fluid would be boiling.

Bill

 

I lost one bolt and one back out, I thought I hit some debris on the freeway turned out to be a bolt letting go. I was lucky because I didn't check it and drove two session on the track menus that one bolt I didn't notice anything but I usually cruz at 150+ mph. I had no issue using a 1 piece pad but I was glad I had an slight moment which brought me back into the pits and there someone pointed out my missing bolt and the 2nd one backing out. I will always check the bolts and use a 1 piece pad on the track. BEZ06 it's a good thing you're a good and experienced driver someone else my not have made the quick and right decision in that situation.

 

The easiest thing to do is to switch up to a quality compound on a single pad. Eliminating the padlets definitely helps the situation. To our aggressive track users we highly recommend switching up to a single piece pad.