Corvette Forum : DigitalCorvettes.com Corvette Forums banner

1 - 20 of 30 Posts

·
Registered
Joined
·
746 Posts
Discussion Starter #1
Corvette calipers can not take more then .010 flex in the lip seals or they pump air.
That is total between rotor wobble and bearing play.
Setting up bearings/front by tightening the nut then backing off to the nearest cotter pin is wrong. You are creating bearing play. Someone else post on how to set up the bearings.
YOu also have to use a dial indicator and cheek rotor run out;
To do this buy a cheap dial indicator and magnetic base. Not too expensive and you should have this anyway.
You want to remove the wheel, front for now, reinstall all the lug nuts and torque to proper specs.
Now mount the dial indicator with the magnetic base so the tip rests against the braking surface.
You might use a C clamp and a piece of angle iron to make a place to put the dial indicator.
Anyway mount the indicator, set it to zero and any number that you can remember, now start turning the wheel and watch the indicator. Take the high and low number on either side of the zero you set and add them. Also grab the rotor and wiggle.
If any time the indicator moves more them .001 or .002, that is wiggling and rototating you have a problem.
The specs move up and down but .005 is absolute maximum. My worst wheel is about .003 and most at 1 to 2.
If you have a high spot and figure what is high or low by taking the dial indicator and push and pull untill you know which direction is which and the low spot is where you want the shims. What shims?
Take a pop break, drink the pop and the can becomes a source of shims. Cut the can up into pieces with a scissors, punch a hole the rough side of the stud and put one over the low stud or studs, reinstall the rotor, install and torque the nuts and recheck.
It is time consumming but worth the effort.
Once you get a rotor to below even .005 no matter what you do I put a red dot with paint on the hub and rotor for future taking apart, I make sure the rotor goes on the same spot and the shims stay where they are.
I know this is alot of reading but if you want to learn how to do it properly and how to work on your brakes there is just no other way.
I would gladly give advice to anyone taking the time to do this.
My brakes are far superior to any of you out there but I could help you get the same brakes as mine.
It just takes a little work, not much money but the willingness to try.
I don't care if any of you listen/ care or not but if anyone does just ask away and I will certainly share the knowledge.

Guys I belong to another forum and there are guys there that are very knowledgable and if we run into problems I could call on them. They would help. Brutus, twin turbo, pro south, etc etc.
 

·
Registered
Joined
·
749 Posts
sounds like a good idea. another item on my winter list of projects to do.

what about turning them while on the car? they have machines now that do that and ensure good accuracy. provided, of course, you get someone who is willing to take the time and do it right.
 

·
Registered
Joined
·
2,409 Posts
I'm on the same "other forum" and I know the guys you speak of.

I did the shim thing with mine about 4 years ago and it does help a bunch.

High and low spots on the rotor surface can be cleaned up by spinning the rotor on a lathe and either
1- take a few thousandth's cut with a tool bit, or
2- use an oil stone, some call them sharpening stones, and stone down the surface.

Afterwards use some coarse emery paper and swirl the surface a bit.
 

·
Registered
Joined
·
746 Posts
Discussion Starter #4
Hi biltogo I turned my rotors on a lathe. I just lightly cleaned them up without removeing them from the lathe. I clean both braking surfaces plus a light cut on the mounting surface so I know everything is parallel
If you are holding a stone on emery paper to the spinning surface you are not truing the surface up , just making it look good. YOu are not removing just the high spots. Your hand is following the contours of the rotor.
As for maching on the car that is tough to do. The back rotors can not be spun with the wheels hanging down, no way. Also bearing play can not be eliminated with the rotors spinning on the car.
Put a trued rotor on the car, shim it to almost zero run out AFTER SETTING THE BEARINGS PROPERLY and you will not have problems.
 

·
Registered
Joined
·
2,409 Posts
Norval, you and I may be able to properly cut the brake surface. The two shops I visited to true mine up called themselves machinists, but weren't. The first guy was going to sqaure the rotor with tool bit touch. I asked him to indicate it, and he said that wasn't necessary.:surprised I told the second shop guy to mount the stone on the tool holder and rub away with an occasional oil spay.

That turned out well for me. I only had an average of .0025 of high spots to match down to the low areas
 

·
DC Crew
Joined
·
53,220 Posts
Has Corvetteforum.com changed their name to "the other forum"?:rolling:

You guys can say CORVETTEFORUM. And, you can link to it. Won't ruffle any feathers around here.:thumbsup:
 

·
Registered
Joined
·
1 Posts
Brake info.....

hey norval........
I was curious as to what I was reading on your post, and I have had brake problems with my other cars, not my vette, but only cause its still being rebuilt:excited:
but id like to learn more about the shimming and measuring process your talking about, and how to do it myself a little more in-depth. now I've never really messed with the brakes all to much other than your occasional replacing the pads and bleeding the system, and I've gone as far as removed and painted the calipers. but not too much experience with the hub play down there, and didn't even know that could be a possible problem of wearing brakes.
what dose this tool you use to measure this look like, and where can I get one. but id still like to hear more as to how to do it right. and if it makes that much of a difference, ill make the time, cause id prefer to do work on my cars myself, cause it just a trust factor I don't have for the person working on my car that I don't know, or if he knows anything, and getting screwed by what your getting that has to go back time and time again to fix the same problem.
if its too much to put here, then you could shoot me an email to [email protected]

thanks for your time:thumbsup:
Dave
 

·
Registered
Joined
·
746 Posts
Discussion Starter #9
I will answer this tomorrow. I just got back from a car show and a nice 90 mile run in the vet averaging about 90 mph for the entire run. It puts me in a high but I better spend some time with the wife.
I will get into this tomorrow.
Have a nice evening.
 

·
Registered
Joined
·
746 Posts
Discussion Starter #10
Guys I did not forget it is just so busy around here with the new term starting.
I also want to post on how to tighten wheel bearings and this is very important.
Do this first. I will run a new post on this proceedure.
 

·
Registered
Joined
·
10 Posts
Not to sound like a jerk but to use an aluminum soda can for shims, doesn't seem to prudent to me. :surprised:
I think I would rather spend the money to buy some decent racing application O-ring brake calipers (as opposed to leaky original lip seal calipers) some good pads and a set of powerslot rotors. That should be plenty to stop well.:D :thumbsup:

Disclaimer: I did not read the entire post thoroughly....so I may be way off base.
 

·
Registered
Joined
·
749 Posts
altho truing the rotors is a good idea, steve, it depends on your application. are you driving your car at 130mph alot that you need to have the best brakes? are you racing? one can sink alot of money into brakes alone, but what are you running for hp?

i liked the idea about truing them and, being a former toolmaker myself, using the aluminum for shims was a good idea. the theory behind it to keep the rotor true was right on. any "wobble" will cause the caliper to draw air...a major problem with most C3 vettes. i've read many posts about people having brake problems and perhaps a simple fix like truing the rotors is the best solution.

anyone who owns an older vette by now should have upgraded to a stainless steel insert caliper. if not, you're asking for problems. it was a poor design back then. i felt it should have been a "recalled" item, but that's just my opinion. the cast ones will eventually pit and draw air..period.

for the little bit of time it would take to true a rotor as norval stated the benifits would be worth the time. MHO

sinking 1000's into brakes on a stock cvorvette might be going too far. in his case he's running 900hp....hell, i'd want the best stopping power myself if i was running that. MHO :cheers:
 

·
Registered
Joined
·
746 Posts
Discussion Starter #13
Guys I don't have a ton of money in my brakes. I have the 4 stainless calipers, a $50 hydraboost out of a 94 one ton truck, all new brake lines, I do NOT run a proportioning valve and the front of the master cylinder is hooked to the front brakes and the back master directly to the rear brakes. This gives 100% braking to the rear and 100% to the front.
I run perfectly trued and shimmed rotors, wheel bearings set to no more then .001 front and back, drilled rotors that a 3 pounds lighter per rotor then stock and ORGANIC PADS, wagner replaced each winter as part of routine maintenance and my brakes will match anyone's My wife's new Bonneville SSEI supercharged feels weak in comparison.
I do not feel that if our brakes are set up the way they were meant to they a a super setup that does not need replacing.
Guys the hydraboost along with no proportioning valve really boost our braking power.
At 80 mph I paniced recently and locked all 4 wheels up, maybe not a good idea but the power is there.
I do give test rides and let others drive the car.
 

·
Registered
Joined
·
749 Posts
altho i mght agree with some of the mods, i'd be a bit hesitant to remove the proportioning valve. removing it will allow the brakes to lock up...something you don't want on a wet hi-way. matter of choice or driving conditions i would imagine.

i will do what you suggested on truing the rotors this winter when i go thru the car, it sounds plausible, so your reasoning for doing it makes sense.
 

·
Registered
Joined
·
10 Posts
I actually printed and read the whole post thoroughly (finally).
Now I see where you were going. Rotor wobble causes the caliper pistons to be pushed back, therefore causing a "long" brake pedal.
As far as calipers stand, I still say invest a couple hundred dollars and replace the out dated original lip seal designs with some good stainless steel sleeved O-ring design calipers. The chance of air getting into your system with the o-ring design is slim to none. They are a much better design. As far as soda cans for shims, I still don't like it but if it works, hey, use it!
I see where your are coming from now Norvalwilhel and I concur with your theory!:D
 

·
Registered
Joined
·
746 Posts
Discussion Starter #16
Thanks Steve. I really don't use pop cans for shims, I have a complete set of brass shims in almost all sizes but I am thinking about the average person who might not have access to brass shims. The pop cans work fine. All you are doing is trying to take up space on the low spot and pop can shims work ok.
I also believe in the stainless steeved calipers but my arguement is that set up properly they are a good caliper. The average man does a half assed job , that is one of the reasons they cause problems, that is one of the reasons the factory went to floating calipers.
Once again done properly the stock caliper is very good.
From lost of experience I have seen lots of cars that have almost no braking on the rear.
Remove/cut a front brake line and try to stop the car. Almost impossible. Take off one of my front lines and you will hardly notice the difference.
In the past I run stickly big street slicks on the back, supposidly know for their bit yet when it came to braking they did nothing. Why not put those big back tires to work.
When the brakes have the proportioning vavle removed you can feel the back biting. It feels like someone is grabbing the back bumper.
I also NEVER drive in the rain. Never.
Bleeding is also alot easier. Try jacking up the rear of the car, have someone hold the brakes and try turning the wheel. Twice I have run into problems that even with the motor running the brakes locked and the wheel still turns over.
75's don't really have proportioning vavles, they seem to be just warning/balancing between back and front but it sure made a difference removing it.
Even when you bleed the system, doing one end, one still open and the peddle feels fine.
This has been argued time and again and I seem to be the only one who has done it both ways and I am giving my experienced opion. Not my gut feeling but a experimented opion.
 

·
Registered
Joined
·
198 Posts
I passed on your info.

Norval...I had cause to pass on some of your invaluable brake info today to one of my fellow club members here in Oz. Here is the link to our short discussion where I also sent him the link to this thread.
http://www.nswcorvettes.com.au/forum/viewthread.php?tid=772
Btw, if anyoone feels like dropping in and visiting our modest little forum we'd be glad to give you all a hearty Aussie welcome.
Crikey!!
NSW Corvettes Unlimited

Bob
 

·
Banned
Joined
·
1,873 Posts
pop can shims will work fine, I always cut up old feeler gauges (I have a buddy that has a machine shop and they throw them away regularly so I can use them for cutting shims, no guessing at the thickness either :) )

As for brakes, I too have a 50$ hydrobooster off the junkyard with a C4 master cylinder on it, a KRC powersteering pump and Wilwood Integra 6 & 4 calipers. I think I'll have plenty of stopping power.
 

·
Registered
Joined
·
746 Posts
Discussion Starter #19
Brutus my information might just prove to be invaluable:laughing: :laughing: I visited the forum and book marked it for future places to drop in. It is miserable here this weekend and glad the vet is put away for the winter. I am working on my rear coil overs .


Twin Turbo you will have lots of brakes, I just have the stainless sleeved calipers with a 94 one ton truck hydraboost and I feel my brakes are STRONG. I have to warn first time test drives to watch the brakes until you are use to them.
The 6 piston front calipers would be even stronger.
Have a nice day
 

·
Banned
Joined
·
1,873 Posts
Norval, good info in this topic. The only thing, the red dot. Paint wears and once it's gone you can not see where it was. I stamp a mark (usually an x) in the rotor hub (outside) and on the brake hub and then go voer the marks with a die grinder and sanding wheel (those flapper type things) to smooth out any burrs. The stamps will never wear off :)
 
1 - 20 of 30 Posts
Top