In the beginning of June the wife and I did the HRPT. Long hauled it again this year. Did about 3500 miles in the 65 and had a great time again. This year we had problems with the brakes. I kept losing the front brakes. Luckily I had put a dual master cylinder on the car a couple years ago just for safety sake. Glad I did! The front callipers would get so much air we completely lost the front brakes and no visible leaks. We bleed them out at one of the venues and lots of air in both front callipers. Had a hard time getting them to bleed but got it done. Nice hard pedal again. Next day no front brakes. We stopped on the route, got a master cylinder and put it on at the next venue. Had a very difficult time bleeding again but got it done. Nice hard pedal and away we went. A couple days later I started to lose the front brakes again but I could pump them a little and bring the pedal back. We took it easy and finished the tour. By the time we got home the fronts were gone again. I bleed the fronts again and only the right front had air this time. Lasted about a day. I finally got a chance to pull the wheels today. This is what I found.

Don't see much here.




Or here.



Holy Crap!





Brakes are worn on all four corners like this. Both fronts and left rear into the rotor on the inside surface! I could not believe it. What causes this kind of wear? I installed VBP O ring calipers and pads on new NAPA rotors a good while ago. I can't see a reason for the irregular wear. The pads fill the calipers without dragging. The retainer pins were all free. Only thing I noticed is the pistons are very short so they can tip in the bores. Is that normal?

Thanks
Tom

 

Replace the soft lines.

 

Sounds tto me like very hard pads and very soft rotors. With all that play the lack of brakes could be caused by the worn rotors pushing the worn pads back too far. One pump to take out the extra clearance second pump to slow down, third pump to stop. Bob

 

I guess the pictures aren't clear. The pads are worn on a severe angle. They are over 1/4 in thick on the outside edge and zero thickness on the inside edge. Worn to the point of gouging the rotors. It is worn that way on all four wheels. The pistons in the calipers are angled so bad they seem to have worn the stainless steel sleeves. I have to replace all four rotors and calipers but I don't understand what happened. Is the next set going to do the same thing?

 

It looks like the pads were stuck and not able to slide on the "PINS"?

 

I agree. That's what it looks like to me too but the pads are free on the pins and the pins free in the calipers. What is bothersome to me is the pistons can get so cockeyed in the bores. All the calipers I have experience with the pistons are long cylinders and cannot get angled like these are.

 

A phone call to VBP tomorrow morning would be my course of action. When you find out what caused the irregular pad wear, please let us know. Some of are using the same equipment.

 

x 2

 

That was my plan. I will let you know what they say.

I don't understand about "replacing the soft lines". How would that cause irregular pad wear? And, I guess I didn't mention it but I am using stainless braided lines installed with the calipers, pads and rotors.

Thanks
Tom

 

I said "hi" while your car was being worked on by the GM motor medic's... glad you made it home safe. I've never seen pistons wear like that. It seems like the pads have to "shift" to put a unnatural side load on the pistons pistons should just squeeze, with minimal side loading. Were the pads tight enough on the slide pins? were the calipers shifting on the mounts?

 

A few things come to mind. Do you have the correct master cylinder in the car? If so, is the rod adjusted correctly? If the rod is just a little too long, it could create a drag causing the problem. It would be more pronounced during periods of sustained driving. Did VB&P rebuild the calipers? It looks like the springs are missing or too weak. If you rebuilt the calipers yourself, did you get new pistons? If I remember correctly, the pistons for O-ring calipers are not the same as stock pistons. Lastly, could your front bearings be bad or not adjusted correctly causing severe caliper run out? I am scratching my head on this one. Keep us posted. Jerry

 

Hey Matt
Sorry I did not get much time to talk. The brakes were driving me crazy!
Calipers were tight and pads loose on pins.

 

Calipers are VBP O ring purchased from Corvette America. The springs are behind the pistons or at least on the one I took apart they are. Wheel bearing are about a year old. Timkin USA bearings.

 

No first hand experience, but I've always heard that slightly warped rotors will continually "pump" the pistons causing air bubbles and loss of brakes. Worth a look with a dial indicator.

 

I don't know why your calipers wore like this but replace the calipers or have them rebuilt.
As noted in earlier post, if the brake pads don't slide freely on the pin you can cause this type damage.
Caliper pistons should fit tight, the pin should be lubricated with a high quality silicone grease that holds up to the high temps of braking and it should be smooth, any burrs can hang up a brake pad. I think your Master Cyl is probably fine, fix the calipers and rotors and see what you have for brakes. I would inspect the rear brakes also, they have been working overtime to compensate for lousy front brakes.

 

Something is rotten! There is no way in hell that those pistons should be rocked that far off center! There has to be something wrong with either the bore, or the pistons. The wear pattern is clearly a function of the pistons being crooked in the bores.




Regards, John McGraw

 

Looks like the pads have been locked in the open position(as shown on the picture)on the pin and only pressed the lower part of the pads while under braking

 

You might want to break the caliper halves apart and look at them. Maybe they were bored out off-center (too low) and the sleeves and pistons are sitting below center of the pads. It doesn't hardly sound possible but that is some strange deal. And you replaced the wheel bearings a year ago so apparently all of that wear is in a years worth of driving? Either you really rack up the miles on your car or those are some really messed up calipers. It will be interesting to see what the supplier has to say. You should email these photos to them.

Dan

 

Power tour troubles..

 

It shocked the h*ll out of me. I've never seen this before. Here's a picture of one of the pistons. The contact area around the seal so short there is nothing to keep it straight in the bore. Are stock lip seal pistons made like this? Seems like if a pad starts to wear unevenly for whatever reason the piston will just tip in the bore. It will not apply even pressure across the back of the pad and correct itself.