Corvette: C3 brakes

"GBannish" <com> wrote in message
news:aol.com... 
into 3 
after 
ft/lbs

No doubt you had the rotors removed from the hubs and then turned. Your
only course is to correctly align the rotors to the hubs, then either rivet
them back together or bolt them by threading the rivet holes, and then take
them to be turned again using the hubs or the rear spindles to ensure they
are true to the axle centerlines.

It is too late for you, but for anyone else, unless your rotors have severe
damage, there is no reason to turn the rotors on a Corvette. there is only
so much thickness that you can cut off and then you have to throw them away.
Then you come up with runout problems when installing new rotors.


Another option is to send them off to Bair's or to Van Steel and let them
fix them.

 
the 
couldn't 
turn the

With the suspension hanging down, the half shafts have rotated until the
u-joints have hit the limits of their travel. You will have to jack up each
wheel and hold the trailing arm with a jack stand. Then they will turn.

 
caliper 
leak. I 
left 
fluid 

Go dig your original bleeders out of the trash and re-install them. If it
ain't broke, don't fix it.

Or did you install some of the automatic bleeder screws that help you bleed
brakes?

Other than that, it is impossible to say without seeing it.

 

Thanks, your answers sound very reasonable. I turned the rotors because the
car had sat for many years developing alot of rust on the rotors, and because I
hoped to reduce the runout. I think I increased the runout a little, at least
on the front rotors!!

I recorded the alignment of the rotors on the rear, and was all ready to
measure the runout and shim as necessary, but then I couldn't move them! I'll
try putting a jack on the trailing arm as you suggest. I bet that'll work.

The bleeder screws have me worried. I'll put the old ones back on and see if
they don't leak, but they're all stripped and I would prefer new ones. I'd
also not want to tighten bleeder screws to a rediculous degree. There must be
100 posts about bleeder screws breaking in half inside the caliper because they
were on too tight, but only one thread (in1994) about bleeder screws leaking
fluid due to a bad seat. Maybe I should coat the threads with teflon tape or
antiseize and then tighten the crap out of them!
Greg

"GBannish" <com> wrote in message
news:aol.com... 
the 
because I 
least 

In the future, there are two ways to handle this.

Take a sander and knock off the heavy rust to where they are clean. The
sander won't cut deep enough to mess it up.

Install an old set of pads, take the car for a 5 to 10 mile ride, and when
you get back, put in the good pads.


 
I'll 
work. 
if 
I'd 
must be 
they 
leaking 
or 

Bleeder screws do not seal by the threads, but by the seat. It could be
that the seat is rusted or pitted and that the old bleeders may have tuck
when you took them out.

If the other new ones are sealing, then leave them in of course.

Thanks for the responses. I found that only 3 or 4 of my bleeder screws were
leaking, so I took those out and examined the end that's supposed to form the
seal. There was a little scoring on them. Then I stuck a qtip into where the
bleeder screw goes into the caliper and tried to clean out any dirt that might
have been caught around the seat. Then I coated the threads of the bleeder
screw with a tiny amount of antisieze and tightened them pretty dam tight.
After rebleeding the brakes, only one bleeder screw now leaks, and it's a very
slight "weepage" after hard pedal pressure.

As for the rear rotors, I can now turn them after jacking up the trailing arm
to allow easier cv joint movement (thanks for the tip!). I think I'll be able
to reduce/eliminate runout by adding shims as necessary, but I haven't done
that yet. That and the parking brakes will be for next weekend.

After fixing the brakes, I was able to take the vette for my first test drive
around the block. What a feeling!!

Thanks,
Greg
Greg

YOU SHOULD HAVE ZERO LEAKS. DO NOT DRIVE UNTIL YOU HAVE SOLVED THIS
PROBLEM PERMANTLY..........

Hope you're still coming back to check this thread.
The bleed screw leak thing is quite simple. Switch the bleed screw in the
leaking caliper for one that's not. If the leak follows, replace the bleed
screw, if it doesn't replace the caliper, it's probably cracked.
As to the rotors, DO NOT SHIM to take out the runout. What this will do is
transfer the runout to the wheel. What's .007 at the rotor will probably be
..030 at the outer reach of the wheel.
Here's the procedure. Disconnect the half shaft from the stub axle. Remove
the rotor. Set your dial gauge up on the face of the stub axle flange and
check it first. While you're at it, check the end play on the wheel
bearings by pulling back and forth on the stub axle. I can't remember the
allowable max, but I think it's less than .008. Now turn the axle making
sure you're holding the axle in or out so that the end play in the bearing
isn't confusing your runout check.
If all that checks out, .001 or less, clean all rust from the axle
flange that might stop the rotor from sitting flat on the flange. Now start
with a visible exam of the rotor. If the cooling vanes (between the rotor
braking surfaces) are heavily rusted where you see large pieces of rust
flaking off, throw it away. Even if there is sufficient material to turn
the rotor true again it will not stay true. If it passes the first test,
use a micrometer to measure the thickness in at least 4 places around the
rotor. If the measurements show that it's above the allowable minimum
thickness all around, thoroughly clean the rust from the surface that mates
to the axle flange and install it on the flange with all 5 nuts. Do not
over tighten. Mount your dial gauge and check the runout, again making sure
you're taking up the wheel bearing slack so as to not throw your readings
off. Mark with crayon on the outer edge the high spot. Remove it and take
it to the lathe. Once mounted on the lathe make sure you now have the same
amount of run-out and the high spot is in the same place, using your dial
gauge again. Once trued on the lathe measure it again with your micrometer
and make sure that the amount removed didn't put you below the minimum
thickness.
Mount it back on the car again with the wheel nuts and re-check the run-out.
Run-out and thickness variation are more critical on Corvette brakes than
most other cars because they use a floating piston design as opposed to a
floating caliper. The piston seals are lip type seals instead of square
cut, which means they seal in one direction only. The pistons constantly
being batted back and forth in their bore by excessive runout/thickness
variation will pun air into the system. You will bleed your brakes and
they'll be fine for a while and gradually get spongy and soft.
Hope this helps.
Steve
BTW where are you. I have relatives by the name of Bannish in Selkirk, Mb.
Canada.


"GBannish" <com> wrote in message
news:aol.com... 
into 3 
after 
ft/lbs 
the 
couldn't 
turn the 
caliper 
leak. I 
left 
fluid 

BTW, contrary to what was mentioned earlier, you do not have to remove or
replace or thread the rivet holes. The rivets that originally held the rotor
to the flange were done that way from the factory for original machining and
ease of assembly. Obviously with the wheel bolted to the flange and the
rotor sandwiched between it's going to be held tight to the flange. The
absence of the rivets is why you need to put the nuts back on when checking
the runout.
"Steve G" <com> wrote in message
news:WB6sb.368696$.. 
bleed 
is 
be 
Remove 
start 
mates 
sure 
take 
micrometer 
run-out. 
Mb. 
turn 
rear 
longer 

Well thanks for the additional information. I hadn't considered possible
consequences that rotor shimming would have on runout at the wheels.
Apparently others haven't either, as this has been posted in several places as
a standard practice. I think I'll try to disconnect the half-shaft and
carefully measure the runout as detailed in your post. If my rotors aren't
true I'll just buy some new ones (they aren't all that expensive). I was
avoiding that because someone warned that even new rotors may have too much
runout in them (perhaps if they were dropped).

Amazingly I did follow your description of floating calipers, as I recently
finished overhauling all of mine. That was a pain, and although I'm not
confident that the recommended RTV sealant will work to seal those outer seals,
who am I to question the GM shop manual??!!


Greg