mrvette

'72 vert, owned in '95 bought with SS calipers all around, lip seals, which always leaked, so after about two attempts I tried the then 'new' O ring piston conversion....no more leaking left brake hose went collapse on me, so I fixed the left front resulting mess....

years later the new rotors had a VERY weird wear pattern....on both of the inside surfaces, not visible from through the wheel, but the INside rotor surfaces on both sides were very badly worn on the INNER/small diameter of the braking surface...and the pads had a very definate taper to them...worn down to the metal on the INNER circumfrance of the pads, right where they wore down so bad they went metal to metal before I heard it....this is on both of the INNER braking surfaces....the pads were OEM thickness as observed from the outer edge, like when changing a tire, near the pad retaining pin...full thickness looking....the pistons were cocked over so badly one side was stuck to the point of tapping with a hammer to get them to straighten out again.....keep in mind the OUTER pads on each side were totally normal in wear pattern and function.....

So I pulled the rotors, finding a pair of old OEM ones in the storage shed, and put them and new pads in place, car drove totally normally and no odd sounds.....

about a year or so later, I hear squeeling from the left front caliper when backing outta the garage.....pull the wheel, and find on the LEFT side ONLY, that the new pad had a kind of knot in the very middle of the pad, not near the pistons at all, and that knot in the pad material had worn a divot in the MIDDLE of the braking surface, on the rotor.....the pad was slightly worn on both outer edges going length wise, the inner circumfrence wear was same as outer...material looking about 3/8 thick and at the ends down to maybe 1/4 inch, but that 'knot' in the middle was round and extended to the OEM pad thickness at least a 1/16th inch thickness difference....I left the rotor and changed that pad.....

NOW it's back to the squeeling when backing out of the garage.....

btw...the brake 'proportioning' valve was nothing but a warning switch and it insisten on leaking years ago, so I put in a simple splitter for the front lines, and put the back line to the master cyl directly...rear most port, first to be applied upon stroke, and the front to the front port...I use DOT5 fluid to forstall rust .....and I converted to Hydroboost brakes years ago......

all this time and the REAR brakes have never been an issue.....

anybody any clues???

bazza77

So you just changed the rotors ?

If you had trouble with pistons in their bore ,that sounds like the bore is worn ? or the pistons are out of round ,or a combination.

Only thing I can think of would be to measure all the front bores (8 of) and all the pistons and see just how much or any difference is .

Usually a stuck piston will wedge the pad along the rotor kinda front to back .

I have had wedged pistons before (when i first got the cars) and just threw them out and put new ones in and with a polish of the s/s sleeve they are still good to today .

As for the knot in the pad , probably the only pad in the usa like it and it ended up on your car

mrvette

The knot is a mystery....much less it digging out the rotor......

I have two rotors on order....so in a week or two maybe I can make some sense of this crap.....pads are being obtained locally....

the pistons were cocked 'looking' to the outside of the radius, so to speak, so that surface was forcing the pads on the inner edge of the rotor circumfrence more than the outer edge....trick IS WHY????

and so to maybe get new O rings, and some lip style backer springs???

I can't see for the life of me that the booster, m/cyl. or that silly warning switch makes any difference in the overall braking/wear and tear......

DUB

Wishing that you took photos of the pads.

The only thing I can think of is you have issues with the pistons on the inside of your calipers.

Wedged pistons are not a good thing...and this is one reason I do not like the 'O' ring design.

I check the run-out of the rotor....regardless if I am installing lipped seal caliper or if the car already has 'O' rings style calipers.

I also make sure the rotor is NOT below minimal thickness....which is 1.215" A brand new rotor is 1.250" and the least you can turn one down is to 1.230".

DUB

DUB

Unless for some reason you are actually applying front pressure to the calipers even when your foot is not on the brake...or bad hoses...not flowing correctly.

I had a 1987 come in my shop and when I raised the hood...I could hear the brake fluid boiling..and then all of a sudden the front brake hose popped off the caliper at the crimp joint. Both front calipers where smoking hot...and I found that it had to do with the booster and master cylinder and when replaced...the brakes were fine.

DUB

mrvette

I getting to the point now of hitting a parts house and going nutz trying to locate another caliper off another car that will mount on this one without changes I can't do....I really would like a single piston floating design, this old aircraft knock off design is for the birds.....

gg521

On post #3, you are suggesting that you try backer springs?? As far as I know, backer springs are supposed to be used with O ring pistons. Years ago, I tried some pistons from Zero Tolerance, which did not use the springs but were used with residual pressure valves. Call Vette Brakes and see what they suggest for the O rings calipers.

MelWff

this link shows springs are used with the O ring style pistons

http://www.cssbinc.com/images/ads/ho...structions.pdf

mrvette

I dont remember the supplier of my O ring pistons, but they very clearly said no springs necessary....the lip seal springs were weak as hell anyway, and so would have made no difference even if installed, and no springs came with the piston kit......

maybe I need to order another kit go around.....funny that the rears were done at same time and never missed a beat....