gcusmano74

Years ago, Stainless Steel Brakes Co, Clarence, NY, made a shim kit specifically for the rear rotors of C2 and C3 Corvettes. I believe they were the first ones to put stainless sleeves in the Corvette calipers, as well. Are they still around?

oldchev

[QUOTE=noonie;1579299665]
(The rears were not an issue with most cars back then, they had drums)

Your memory is going back a little further than mine. We're talking about cars that have disc brakes on all four.

(Same holds true for the C3 front rotor and spindle, riveted or bolted together )

I could maybe agree that there is some measurable rotor run-out involved with two piece spindle and hub flanges and rotors. But just as another note of experience, I have repacked my front bearings about every 3 years for the last 27 years. Each time making no attention to where the rotor is reassembled to my front hubs. Each time have never used shims and never needed to bleed the brakes after removing the calipers and suspending them temporarily on a hook without disconnecting the brake lines. My front calipers and rotors are about 15 years old and my rear calipers and rotors are over 25 years old. I put new rear wheel bearings in about 20 years ago. The one spindle is original to the car and the one I did replace. So there is quite a variety of parts there, from different eras and vintage. I drive the car as a daily driver every summer. So if your bearings are loose, or your rotor has too much run-out, fix them. If your spindle flange is bent, as one of mine was, replace it.

Can you tell me where to buy the shims to shim the rotors?

Thanks, Dave.

Peterbuilt

NAPA sells these:
http://www.brakealign.com/

gbarmore

These look great, has anyone tried these? I did a quick search at NAPA.com and did not find them.....

Peterbuilt

http://www.napaonline.com/Catalog/Re...&Dk=1&Dp=3&N=0

Or you can use a soda can.

chucks

Rock Auto has the shims.
http://www.rockauto.com/catalog/raframecatalog.php

gbarmore

Perfect, thanks guys, I like the idea of the tapered shim that supports the entire rotor vs the soda can shim that only hits one spot. I did try it today and it worked, just not 100 comfortable with it and for a few bucks more I'll go the Brakealign route.

Buddy1980

Ok guys, here is my experience with rotor runout and how I managed to correct it. I had 6 front C-3 hubs, and also 6 rear C-3 axles. These were all used parts, and I wanted to pick the best ones to use on my car, as far as runout was concerned. I set up my front and rear new bearing assembly with zero clearance for measuring purposes, and one by one, checked all the front hubs and rear axles for runout. What I found was totally amazing, the runout on the hubs and axles ranged from .006 up to .015, which would put the rotor runout anywhere from .015 and up, assuming the rotor was machined to zero runout on its own. Now keep in mind these were 30 year old hubs and axles, which who knows what they have been thru as far as abuse with curbs, collisions etc. So I took the 2 hubs and 2 axles with the least runout to my trusty machine shop. They took the rear axles, chucked them into a nice looking CNC lathe, and trued the mounting face. The front hubs were another story, they could not be easily mounted to the lathe without some cones to center on the bearing races. So I took the front hubs to a car repair shop that had a nice rotor turning machine, and they used this machine to true the front hub face. I then took the machined parts and remounted them to the car, put the dial indicator on both front hubs and both rear axles, and presto, all four checked with less than .0005 runout. Now remember, this was with zero slack in the bearing assembly. I set up my rear bearings with .001" clearance, and also tried to keep the front bearings as tight also. When I installed four new rotors, which came straight out of the box, and checked them on the car with the indicator, I had all four check with less than .001 runout. After looking at these parts and what I had to do to properly fix the problem instead of shimming etc, I agree with some of you about the rotor and hub/axle assembly being machined together at the factory. This would result in the hub/axle and the rotors not being a trued part by itself. It would be interesting to take 10 new hubs and 10 new rear axles and check the runout on those to see what if any they had. Keep in mind that if the hub or axle is off .005", then the outside rotor edge is going to read approx. .015" runout. So FWIW, this is how I got rid of my rotor runout. I will add that as of lately, all of the rotors that I have bought new for any vehicle, including Corvettes, have checked with little or no runout. These include C6 Z06 rotors, C3 rotors, Jeep rotors etc. Some of these were even the $18.95 cheapo Autozone specials from China. Anyway, I hope this will help someone. Good luck.

Mike Ward

They were probably like that from new. Thanks for the info. Hopefully people will understand that simply swapping rotors and not measuring/fixing runout is just looking for problems.

noonie

It is a gross misconception that the oem axles and rotors were not machined true as separate parts and seems to be perpetuated by internet folklore.

It is virtually impossible to machine new axles with any measureable runout. Any junior machinist can verify that.
My neighbor has a 150 grand cnc turning center and spits out high production parts to 2 ten thousandths all day every day.
The flanges are not that strong compared to other vehicles and as you mentioned will get distorted thru common use or possibly even by the original factory riveting process. You can check any axles or assembly with just "v blocks" and a dial indicator.


If your bearings are within specs, easiest is to use a proper "on car lathe" for the rear and a regular brake lathe that's in good shape for the front and not worry about the axles or hubs that much.

Glad to see you did it the right way though.

Mike Ward

Then how do you explain the large number of high mileage cars that have little or no runout (as measured on the rotor friction surface), yet a high amount of runout on the flange when the 'never-disturbed-since-new rotor is removed?

tracdogg2

Next time I machine some spindles I'll take a pic and you'll be able to see how bad they actually are.
Mike

wombvette

I tend to agree with ya noonie, there will not be much on a newly machined axle, but in this case even one .001 or so run out at the hub will translate to several thousands at the rotor surface. That is why GM assembled the rotors and final machined them together as a unit. They were trying to hold it to .001 or less. They even state in their repair literature that they should not be serviced in the field, but should be replaced as a unit. They knew what the problems would be in the field if someone removed the rotor and machined it separately and they cautioned against it. Fact is that most of them taken apart and reassembled today have run out and need some adjustment. Those of you that have done it and not had to adjust them are just lucky.

Ironcross

all you need is a good brake lathe to true the rotors {and drums}.......and the hang on the car stuff is a pain in the *** and takes too long whether or not there's any benefit....and whats the back alley fix for heat warped rotors?...throw them away?

gbarmore

Guess instead of going out for a little joy ride on my favorite undulating, windy country road (where I finally can get back out of the car some of the blood, sweat and tears that I put into it), I'll just park it in the garage and rev that beautiful refreshed 350 and take a nap in the exhaust gas. Can't mess up my runout doing that.

Thanks for wrecking that drive time for me ironcross

noonie

It would be nice to check on v blocks, an old stock original oem GM spindle that had never been riveted. I assume GM bought the completed assemblies with rotor mounted from a supplier. Probably also why you couldn't get them separately and why GM recommended unit replacement. The flange design is rather weak as far as axles go.

I don't know of too many machine shop lathes that you could just stick one of these axles in the chuck and be ready to go. (I've done it). Best is to use the original centers or make your own jaws for a large enough chuck to tag both bearing surfaces at once (different diameters).

It's futile to second guess GM's strategy, but it's obvious that the original spindles were machined between centers using a type of dog drive. It's still the best method, since it requires remounting in the lathe or dedicated machine, after rotor install, with no loss of accuracy.
This type of mount can assure runout of only a few ten thousandsth (known as tenths) .0001"
The rotor pad area may well have not even been machined at this stage, just the mating surface and holes. The riveting process may well cause runout on the spindle flange in itself. It doesn't take much, I can cause a couple thou with a hammer on a flange. With that in mind removal of the rivets and rotor by the common method of drilling the heads of and punching out the stem can cause runout.
The rotor pad area may have been machined for the very first and last time after being riveted. Just a cost effective manufacturing procedure, nothing more elaborate than that.
There were many axle manufacturers in the Detroit area an surrounding states, US, Southwest, BorgWarner, Skyway, NTK, Lafere, Eaton, Dana (Spicer), American, SG, etc. Gm probably used more than one or at least had a backup.

With the rather recent popularity in separate rotors, the runout problem is more popular than ever on almost all cars, mostly from rust, and sloppy repairs, hence the simple fix, on car lathe.

Richard Daugird

I have been doing research on brakes and this is one of the most interesting threads I've come across.

mysticpete

Hi all
After just completing a body off resto, I have finally been driving for a few weeks and noticed a squeaking from the rears, now even tho I did check the run out it would appear from turning the hubs that there is considerable runout and the squeaking is indeed the pads moving back and forth across the locking pin.
So thanks to this really enlightening article I will try and address the issue, and of course will convey my results, your advice and help is appreciated.

mysticpete

Now heres a question for you all....

Where do you set the dial gauge on the rotor, edge middle or inner?

I have to take two readings, edge and inner as the rotors are slotted.

jim-81

Here is a thread I did on this (as I was learning)
https://www.corvetteforum.com/forums...out-shims.html
Jim