Help! Brake Job: New Rotors or not

[401KVet]

;help I bought this, my 1st Vette last October. The previous owner said that new brake pads, front and rear, along with calibers were put on the car just before I bought it. It had 42,800 original miles on it at the time.
It didn't take long after I got it that I noticed a vibration in the steering wheel along with a slight shaking in the car when braking. Normal braking you feel it just a little, but if you have to hit it slightly hard like at a red light that you are trying not to run the worst it is. Not being the greatest mechanic I knew enough to suspect the rotors. After getting the front and rear end aligned, they at the shop also told me I had a problem with the rotors, probably warped.
Not knowing about a C3 brake job, I took it in for one. They found all of the rivets still in place, and the shop decided they did not want to mess with it. Apparently new pads had been put on the car because they still had plenty left, but the rotors were not turned. Anyhow my belief at this time is that they may be warped. I have been told do not mess with C3 rotors unless you absolutely have to. They were make to last.
Anyhow I drove my Vette home not doing anything yet about the brakes.
I would appreciate some advice from SOMEBODY WHO KNOWS SOMETHING, because I clearly don't. :W

 

[Copdogcorvettes]

I'd advise you find a shop that actually knows what they are doing. Drilling the rivits is no big deal; just a pain in the ***. Yes, the stock rotors do last a long time but, when it's time, it's time.

Gary

 

[geekinavette]

I don't know much about C3s...but on other cars on three different occasions I have had those exact symptoms. One instance was just warped, the other two times were cracked rotors.

 

[Vettehead Mikey]

It's almost unheard on C2/C3s to have warped rotors, I doubt that's your problem. If the previous owner used cheap jobber pads, this may have left a deposit of material on the rotor surface which provides an uneven friction surface. This can easily be fixed by a competent garage. I think 3M makes a kit especially for this purpose.

In any case, yes you heard correctly, don't remove or change the rotors unless there is no alternative.

 

[geekinavette]

Really...that's quite interesting!

Are they just thicker than the rotor on a "normal" car?

Maybe its the quality of the metal (which we know has gone down the crapper since then).

 

[6880 Mike]

Take the car to a reputable brake shop and have them check the run out on all four corners. They can also measure rotor thickness while they're at it. This will either eliminate the rotors are your problem, or give you a place to start brake work.

Otherwise -- you're guessing.

 

[LT4man]

You need to find a competent Corvette shop. The rear wheel bearings on a C3 can wear and cause a run-out problem which seems like a brake rotor problem. As mentioned above, a competent Corvette technician needs to measure the run-out with a dial gauge.

Rear wheel bearings are difficult to replace on a C3. It is a labor intensive job.

AFTER MEASURING YOUR RUN-OUT, PLEASE SAVE THE !

 

[GTR1999]

I would type it again but I'm getting tired of it, check this thread it should help you understand what you have to work with.

brakes - Corvette Forum

 

[Vettehead Mikey]

Here's the 3M kit I mentioned.

3M Automotive 1410 Roloc2 Brake Rotor Surface Conditioning Discs

As others have mentioned, have the rotors inspected for runout/parralellism before doing anything drastic.

 

[401KVet]

Well, I'm seeing more and more than this is not like just doing a brake job on my 77 Cutlass.
Thanks for all of the input. I can see a lot more clearly now, and it's looking a lot more complicated. :W

 

[Hib Halverson]

"Vettehead Mikey" is right...under normal circumstances--ie: no racing or other severe duty and as long as the rotors are above the discard thickness--65-82 brake rotors almost never "warp". That said, if you think you have a problem with rotor runout or thickness variation, the right thing to do is measure runout and thickness variation.

Unfortunately, this requires some "special" tools, namely a dial indicator and a micrometer and, even with them, is not easily done if the wheel bearings (front or rear) are worn or loose.

At the factory, to limit runout (and probably, also, to reduce cost by cutting the number of manufacturing steps), the rotors were machined with the hubs (front) or axles (rear) in place and the machine work indexed off the axis of the hub or axle. To maintain that index, the rotors were riveted to the hubs and axles.

When people drill out the rivets, then either machine (or "turn") the existing rotors or install new ones, that sometimes doesn't solve the problem and runout remains. This is why "shims" have been available from some aftermarket sources.

Often, since the rotor/hub or rotor/axle assemblies were machined as units, when considered separately, the rotor mounting flange on the hub or axle may not be perpindicular to the axis of the hub or axle. If that is the case, even if the rotor is machined properly, there will be runout. The only ways to solve that problem is either 1) shims or 2) machining the hub or axle flanges to make them perpindicular to their axis.

Sadly, with runout being critical with fixed-caliper brakes, 65-82 brake service can be an expensive nightmare if rotor machining or replacement is required and an axle flange problem exists.

Bottom line...I'd carefully asses the existence of any run-out or thickness variation before I'd drill out those rivets to machine or replace rotors.

Lastly, you may need to address problems with worn wheel bearings, front and/or rear, before you can properly solve rotor runout.

 

[Vettehead Mikey]

Well, I'm seeing more and more than this is not like just doing a brake job on my 77 Cutlass.
[

Yup, C2/C3 brakes are unique and in general cannot be treated like 'other' cars even of the same vintage and manufacturer. Having said that, simply following the instructions laid out will keep you out of trouble and will guide you to the most economical and effective fix.

 

[401KVet]

Well, not I really can't stop my head from spinning! :W

 

[73shark]

Be sure you check that the front wheel bearings are tightened to spec before checking runout.

 

[Rebelrob]

I had a brake job on mine. My back rotors were hardly worn, so we left them alone. They still had the rivets in place. I did replace all 4 calipers with new ones and pads, bleeded, etc. Also replaced the front rotors and repacked the bearings on the front. The front rotors were worn down enough that they could not be turned and be within spec. Brakes are a job you do not want to cut corners on.

 

[Koop]

The rear rotors just got drilled of my '69. The car has a ton of hard miles on it, more than 500,000. They just needed to be turned.

Get a better tech.