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Brake Pad question

I have gone though 4 Raybestos rebuilt calipers in 3 years on my 82.
They leak sitting over the winter in the cold temps and pull really bad on the first drive in the spring. Fortunately, they give me new ones for free to replace them, since they are under warranty. I think Non-/OEM calipers would have done just fine. I hope they are still good when I get her out of storage in a few weeks.
 
I see the complete O-ring upgrade kit at VB&B. Nice kit, and a lot less than I thought i'd spend. Do stock pads fit in that? i.e. can i order any pad that fits 1982 and it fits in the o-ring calibers?

http://www.vbandp.com/detail.aspx?ID=280

that's the kit i found. Looks good.

I love CAC. greatest automotive advice i've ever seen.
Yeah, the caliper housing itself is the same. VB&P does rebuilds the OEM's with the O-ring setup. Thus, the pads are all the same. From the pic, it looks like the kit comes with pads, which I seem to recall mine having as well. And the caliper clips that were mentioned above.

I think if/when you order from VB&P, mention the CAC to get a 10% discount.

(I don't know what the 'insulated' calipers are and why they carry such a premium...)

You can even use the CAC Private Message to contact VB&P from here for questions and whatnot. That'll guarantee you get the discount as they know for sure you are coming from here. It's also good promotion for Rob to let our "Preferred Vendors" know that they are getting mention in our forums.
 
A little over a year ago, I purchased a set similar to the one in the link from VB&P except I got the MC as well. I can say they were great to work with and I was back on the road in a week. That is the time it took for me to take off the old calipers, send them in to VB&P (to avoid core charges) and for them to ship (ground) the new o-ring calipers (and the rest of the kit) back. I had everything installed over the weekend. I recommend using a power bleeder also. I'm a fan of the o-ring set-up over the old lip seal design when your car sits for long periods and isn't driven often. The maintenance history for my car showed the original calipers had been rebuilt several times over the years because the car sat so much, and within a year of me buying the car, the brakes went to the floor one day. I've been happy with the new stuff. I still don't know why they just don't throw in a proprtioning valve with that kit.
 
I still don't know why they just don't throw in a proprtioning valve with that kit.
I made that suggestion to them when I bought my kit two years ago...It's the only part of the system they don't include. I have no idea why they don't. My mechanic said that I could actually do without it entirely given the newer master cylinders being used. (I think that's why he said I could do without it.)
 
There's actually no bearings of any type in a caliper. The caliper itself is a machined cast iron housing, with four aluminum pistons riding inside individual bores. The stock seal are a 'lip' or 'garlock' type seal which is used throughout the auto and aviation world and actually work quite well.

The initial issue with the Corvette application is water, salt, dirt, etc.etc. getting into the cast iron bore. The repeated wet/dry cycles of normal operation causes pitting corrosion on the bore. This eventually becomes more than the seal can handle, and an external leak of fluid ensues.

The cure for this is to re-machine the stock caliper, adding a stainless steel sleeve inside the bore. The stock piston and seal is retained. This simple fix solves the corrosion problem more or less permanently, other than simple old age and dried out seals over a 10-20 year time period.

Another unrelated issue is one where the pedal goes 'soft' and remains this way, or returns shortly after repeated bleeding attempts. The 'lip' seals referred to above do an excellent job of sealing the fluid inside the caliper- much better than any other type of seal. What they are not designed to do is resist contamination from outside trying to enter. If there is an external force that frequently pushes the brake pad back into the caliper, it's entirely possible that air, dirt, salt etc, will get pushed inside as well. The result is seal failure and leakage. Stainless steel calipers will not prevent this, as this failure mode has nothing to do with corrosion of the caliper bores.

The fix for seal failure is to convert from a 'lip' seal configuration to an 'o-ring' type. This may or may or may not also requires using different type pistons that are suited to the shape of the o-rings.

The advantage of o-rings is that they seal equally well in either direction, so to a limited degree, the air and dirt pumping problem is solved. The downside of o-rings is that they do not seal as effectively under high pressure as a lip seal, but in a practical sense this is not a concern on a relatively low pressure application like a Corvette brake system.

One issue that frequently gets overlooked is the root cause of the pads 'pumping' dirt and air into the calipers.

Two main causes for that-

1) a worn rear wheel bearing that allow the axle, rotor and wheel ass'y to wobble back and forth causing the pads to be shoved away from the rotor.

2) a warped rotor (very rare) or a replacement rotor that has not been machined after installation to run 'true' on it's axis(very common).

C2 with disk brakes and C3 Corvettes are very different animals when it comes to rotor replacement. They cannot be changed out in the same manner as today's cars where the old one is tossed out and a new slapped on and and away you go.

Odds are that there is sufficient run out with the new rotor that the pads will be pushed back into the caliper even after a short drive. A soft or low pedal is the result and pumping or bleeding is only a temporary solution. O-ring calipers don't solve the issue, but merely mask it.

The correct solution is to have the new rotor machined in place on the axle and be done with it.

Sorry for the long post. :beer
 
Soft Brake

I took the wheel off and got the old pad out, but getting the new pad in was very difficult. As I compressed the pistons into the caliber, they would pop back out before I could get the pad in. I tried screw drivers, but they didn't work. Finally, I used 2 putty knives to compress the pistons and then slid the new pad down. I'd never seen pistons that would not stay in the caliber after they were compressed (though i've mostly worked on ford truck brakes).

Is there some trick to make the pistons stay in when they are compressed?

Also, my brakes feel "soft." I haven't driven it in a while, so it may just be my imagination. I guess i could have gotten some air in the brake line, but the brakes still work and stop. It just seems like i have to push the pedal closer to the floor. If I want to bleed the brakes, do i turn the bleed valve clock-wise or counter-clock wise to open the valve? I heard it may be reverse threaded.

Thanks for your help everyone!

You may know this, but it is worth repeating: 81 shop manual directs that you always bleed the longest brake line first and move closer to master cylinder with each wheel bleed. I found on my 81 that you need to bleed them more than once, until they firm up. Also my rears have two bleed screws on each caliper.

Hope this helps.
 
Update,

I bled the system. A few pumps on each wheel. The results are amazing. It stops on a dime. The first time I drove it, I nearly threw myself through the windshield.

My corvette has spoiled me in regards to handling. It corners and stops SO much better than my Mustang. (I only bought the Mustang so I could stop using the corvette as my daily commuter. 60 miles a day in traffic is not how a corvette should spend its life).

Thanks for the advice. CAC has saved me a lot of time, money, and frustration. GOOD LUCK TO YOU ALL!!!
 
"The correct solution is to have the new rotor machined in place on the axle and be done with it."

Is this service widely available? It sounds pretty specialized.

Mikey, thanks for the great explanation. :beer
 

Not as rare as you might expect. Might take a while calling or visiting local brake shops, just need to ask them if they can machine rotors in situ. I know of at least 5 or 6 shops in my area (Montreal) that will do it.

There's no real excuse not to. ;)
 
"The correct solution is to have the new rotor machined in place on the axle and be done with it."

Is this service widely available? It sounds pretty specialized.

Mikey, thanks for the great explanation. :beer

My original rear rotors were recently drilled off my '69, always turned attached. Could explain why I havn't cracked the original diff, nothing shaking back there might have something to do with it's long (yet abusive) life span.
 
Not as rare as you might expect. Might take a while calling or visiting local brake shops, just need to ask them if they can machine rotors in situ. I know of at least 5 or 6 shops in my area (Montreal) that will do it.

There's no real excuse not to. ;)

Mickey...,
could you name a few. I'm from the Montreal area also and would like to look into this in a near future.

Thanks in advance....:)
Roger
 
These are the Hunter factory reps for my immediate area (South Shore):

JACQUES BOUHOURS
(450)779-0039
huntertec@tlb.sympatico.ca


ROBERT (BOB) LAROCHE
(514)208-1088
rlaroche1145@sympatico.ca

Trying giving them a call and asking the name of a shop closer to you.

It's extremely rare to actually NEED to turn a rotor on a C3 unless you are trying to undo the work of bubba. You sure yours needs to be turned?

(EDIT)

Here's the machine you want:

http://www.hunter.com/pub/product/lathe/5071T/index.htm
 
It's extremely rare to actually NEED to turn a rotor on a C3 unless you are trying to undo the work of bubba. You sure yours needs to be turned?

(EDIT)

Well there is a little vibration when applying the brakes but, most of all, the rotors are awfully glazed. I've only had the car for 2 years so, not quite sure when the last brake job was done.

Thanks again for all the info.
 

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