I've got my '81 pretty much dialled in now, except the brakes.

They pull to the right under anything more than medium braking. The harder I brake, the more they pull.

I've just bled them completely all round but no change.

They do not leak. (EDIT: Some or all of the part about them not leaking may not be completely true)

Rotors all good, pads all good, no judder, squeal, wobble etc, just a pull to the right beyond medium braking force.

The two callipers on the left appear to be original (car has 42k original miles)...






However the two on the right have been replaced with generic remans...


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I have a few questions.

Is it possible to tell (without stripping) if my original callipers have ever been rebuilt, and if so whether they have stainless liners and or O-rings? If so, how?

If they are original, could it be they are just not performing as per the new ones, hence pulling to the right, i.e the new ones are performing correctly, but the left (front?) isn't up to much beyond medium duty?

What is the best way to tackle this - from the UK where Corvette bits, especially heavy parts like brakes are very expensive due to international shipping, duty etc.

It might be a moot point but for the record, when bleeding them, the front left did not bleed as freely as the other three using gravity bleeding - the fluid came out very slowly where the other corners dripped freely and quickly, where fluid from the front left crept down the pipe very slowly.

 

If you are sure that the calipers are not leaking, then I would suggest you replace the rubber hose on both front calipers. They might look in good shape but they break down inside and act like a check valve.

 

A sound suggestion, however all hoses were replaced recently.

Definitely no leaks.

 

ALSO........
Install quality MATCHING-pads on the left and right calipers before paying big $$$ to fix the problem.
Different pads from different manufacturers can cause "grabbing"

 

Its possible the bleed screw(s) on the slow-drip caliper have some dirt in the bleed-hole causing the caliper to bleed slower....or....there is sludge inside the caliper bores(last resort is to disassemble-i spect internal caliper)

 

"It might be a moot point but for the record, when bleeding them, the front left did not bleed as freely as the other three using gravity bleeding - the fluid came out very slowly where the other corners dripped freely and quickly, where fluid from the front left crept down the pipe very slowly."


That's a red flag to me, I use a mighty vac to bleed my brakes and change fluid. I like to see a steady stream coming out of each bleeding screw when I release the vacuum.. Are they by any chance braided brake hoses?

 

Sorry to drip feed info here (no pun intended).....

The car was in storage and not used for sone time before I bought it and the previous owner/seller did some recommissioning work - vacuum headlight cans/hoses etc, that kind of stuff, and as part of this replaced all the rotors, all the pads and the hoses and for some reason, only the two right hand side callipers.

The flexible hoses are stock rubber hoses all round.

One of the frustrations I had when bleeding the brakes was that air was creeping in through the bleed nipple threads on all bar one of the nipples on the original rear calliper, so I had to remove them all, clean them with brake cleaner and use a thread seal tape just to keep the air out whilst I bled them - a long way of saying the front left bleed nipple is free and clear.

 

Looks like the right front rotor is getting more wear than the left, and even more on the top portion of the rotor.

 

Let's see. Assuming you DID get all the air bled out (which we don't know 100% for sure), there could be a couple other explanations: 1) You could have sticking pistons. 2) The pads are stiicking in the slot which they fit, 3) The hoses have delapidated internally and aren't allowing fluid through properly. Or, possibly the valve is bad. How handy are you?

If it were my car is to quadruple-ensure the system is 100% bled. Just because C3 brakes are notoriously hard to get air out of ...and have antagonized a lot of owners. Could you articulate your bleeding process?

After that, I'd pry the pads back and see if the pads move freely. Your calipers don't look rusty, but sometimes pads 'could' be mis-stamped or have a burr on one of them preventing one from moving freely in their slot. And it takes 10 minutes (and $0) to rule out sticking pds. Plus, if you can't pry the pads back that leads to the next thing I'd look out for: sticking pistons. Pistons can stick due to corrosion or crap inside. Almost looks like that in your pictures. If that were to happen, when you hit the brake pedal, braking would be less on the 'sticking' side ...the car will 'pull' the opposite direction. If you removed the pad you might be able to stick your finger or a dull screwdriver and move the pistons. Any piston that doesn't freely move is suspicious.

If you find a stuck piston, you could remove the caliper and remove a piston. Clamp a piece of rubber on the brake hose so not too much fluid leaks out. Once you have the caliper out, if a piston is tough to move, like rock hard, then you've discovered the problem. You can carefully pry under the piston boot with a dull screwdriver, or dull gasket scraper and remove the dust boot w/o damaging it (for reuse). They pop out pretty easily. then remove the piston. Usually you can pull them out with gentle use of a pliers. If you have a real stuck one, you might want to stick blocks of wood where the caliper would go and apply air pressure to get the stuck piston out (before splitting the caliper in half). You could re-hone the bore and re-use the piston and seal if it still looks ok. Or replace the caliper from an OReilly's caliper (Lone Star rebuilds).

Could also be a hose too although somewhat rare. How old are yours? If you decide to buy replacements, CSSB has the 'right' replacements. GM replacements are import hoses and don't look like originals anymore. (too thin).
https://www.cssbinc.com/corvette-brake-hoses.aspx

 

Thanks for the detailed reply.

All hoses are new.

I'm an engineer by training (years ago) and reasonably handy - can rebuild and engine and rebuilt the callipers on my C4 about 20 years ago.

I can always bleed again to check but went through a full litre of new fluid and several master cylinder top-ups whilst bleeding, whilst tapping the callipers with a nylon mallet etc.

I guess next steps are to remove the pads in the front left, check for freedom of movement of both the pads and the pistons and see what's what. Depending on what I find, I imagine then it's a full strip down and rebuild with likely lip seals if the callipers are original?

 

Good spot - I guess the additional wear would support the front left not working properly.

 

Not really. Just disassemble and see what you have. You might be able to put the same parts back in. Or it might make more sense to buy rebuilt calipers. I'd take apart and then decide before buying parts. I've taken many calipers apart (corvette and non-vette), cleaned them and a light honing (with fine sandpaper) and put them back together with the same seals and boots. Sometimes a new piston though.

 

I will update this with progress and and when, thanks.

 

Before you disassemble anything go get, or make, a pressure bleeder. Really. Since you are an engineer it will be easy enough for you to make one from a garden sprayer, some tygon tubing, an aluminum plate, and a pressure gauge(gauge not absolutely necessary but a good idea and I would install one). YEARS ago I made one just because I did not want to wait for one to ship.... it has worked so well that I never got around to buying a real one. It was inexpensive too.

Last Triumph
You say hoses replaced "recently"; "recently" has no value...so hopefully you mean in the last year. I "recently" did brake pads on my pickup just because they were worn down--I actually had a good brake pedal and all..... afterwards I could not bleed them for ****, even with my pressure bleeder, turns out that just by disturbing and emptying the hoses (yes, both) if affected the hoses to where they would not allow proper bleeding..... replaced them both, pressure bled---- now fat, dumb, and happy. I was surprised.

Anyway --- here are multiple ideas. If you have a piece of steel or aluminum lying about you can make one today since those garden sprayers are quite common at the local hardware stores: https://www.corvetteforum.com/forums...y-version.html

 

Yes, within the last year - about 13 months ago, although the pull has existed from when i bought the car, at which point the rotors, pads and hoses where perhaps a month old or so.

Will have a think about pressure bleeder.

 

Quick question regarding rebuild kits if I end up going that route, this video looks pretty simple, yet there is no mention of stainless steel sleeves?

Are SS sleeves essential and if so, is that not an 'at home' rebuild process?

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unless you are an engineer with a machine shop, installing SS sleeves is not an at-home job. the fact that the pull is toward the replacement calipers makes me think the other 2 need replaced too...

 

Thanks.

Are the callipers in the video above already sleeved?

 

Do the pressure bleeder now or do it later. I would do it before any other experiments. Your call but I highly recommend it. It's cheap and easy since you can make your own.

 

Got any pics for reference?