One of the front rotors on my '67 Chevelle has a number of hairline cracks running across the face. They aren't raised, but this seems unsafe to me. Replacement time, I assume??

The other front rotor looks fine. But the rotors have a number stamped into them -- somthing like .9?? inch (I forget the exact number). I assume this is the minimum size to which these can be turned, after which replacement is necessary? Is this correct?

Thanks in advance for your help!!

Those might not be cracks-- they could be heat checks which look like cracks. The checks are not usually a problem because they are only on the surface.

Do you have a buddy that could turn them for you to check them out? Otherwise, I wouldn't bother having it turned since new rotors are cheap (very cheap!). Sometimes those hairline cracks are just from heat and can be taken out, but without seeing it, I'd advise replacement. You really shouldn't mess around with brake parts. You are correct about the number stamped on the rotor. There is a minimum thickness for each rotor to prevent them from overheating/breaking and they should absolutely not be used if they come out thinner than that number.

Good luck!
Ryan

Heat checks or stress cracks, either sounds bad. If the brakes are in good condition and working properly they shouldn't ever get cracks unless highly abused. I'd strongly recommend replacing both rotors.

I ordered two new rotors. A former owner must have liked living dangerously. The stamped minimum is .980 or so. One was down to about .840 and the other (the one with cracks or checks) to about .740.

Another question. Both spindles have some scoring at the spot where the outer bearing sits on the spindle. One has fairly light circular scoring around the spindle, while the other spindle looks like something dug in one spot, which caused deeper scoring or a small chip. (I'm speculating that the former owner lost a wheel or had a bearing come apart at some point - a lot of things can happen in 38 years).

Anyway, the bearings that came with the car were in good condition and the wheels turned smoothlly. I'm replacing the wheel bearings anyway, but am wondering about the spindles. I expect that spindles are hard to find, so I'm thinking or reusing them. What do you think?

Thanks again.

You should be able to reuse them. Clean them up a little with emery cloth and grease them up good. It wouldn't hurt to check them again in a few hundred miles, just to be safe.

Rotors aren't cheap.... I went to murrys today, and they wanted $50 each. But Murry's sells 2 calipers w/o cores for $10

A new rotor for my s10 was 10 bucks

One thing that needs to be cleared up about the thickness spec that is cast into the rotor. Many people-including shops that should know better-get this wrong.

The number (thickness) cast into the rotor is the THROWAWAY specification. At or below that thickness, the rotor is SCRAP METAL.

When turning a rotor, you need to stop AT LEAST .030 THICKER than that minimum spec, because the rotor can be expected to wear during the life of the pads you're installing.

In short, you MUST NOT turn a rotor all the way to the minimum spec.

Bri2203: $50 a rotor IS cheap. So cheap that I bet they're imported from China--the land of "perfect quality". You can expect minor issues like not enough cooling fins cast into the rotor, or substandard iron. You're much better off with a Canadian or American made rotor, and even then you need to be careful.

Does your S-10 rotor also include the hub and bearing races? I'm thinking they're just a hat that slips over the hub, while on our Chevelles the rotor and hub are integral.

Originally posted by caru68:
You should be able to reuse them. Clean them up a little with emery cloth and grease them up good. It wouldn't hurt to check them again in a few hundred miles, just to be safe. Please don't do any brake work until you have done some schooling on braking systems.....it has already been stated that the rotors are heat checked AND that 1 is .140 under spec and the other is .240 under spec..... :eek:

It would be very foolish as well as unsafe to you and fellow motorists to clean those and run them. There is a reason the limit is called the "discard spec". Throw them away.

Originally posted by Schurkey:
One thing that needs to be cleared up about the thickness spec that is cast into the rotor. Many people-including shops that should know better-get this wrong.

The number (thickness) cast into the rotor is the THROWAWAY specification. At or below that thickness, the rotor is SCRAP METAL.

When turning a rotor, you need to stop AT LEAST .030 THICKER than that minimum spec, because the rotor can be expected to wear during the life of the pads you're installing.

In short, you MUST NOT turn a rotor all the way to the minimum spec.
Just to be completely factual......a lot of manufaters include that .030" "wear factor" into their spec, we always look in the service as it states whether or not that has been factored in or not.

Dennis68, I'm not a moron. I was talking about the end of the spindle where the bearing runs. He stated that there was some slight scoring on the spindle in his second post. Quote:
"Another question. Both spindles have some scoring at the spot where the outer bearing sits on the spindle. One has fairly light circular scoring around the spindle, while the other spindle looks like something dug in one spot, which caused deeper scoring or a small chip. (I'm speculating that the former owner lost a wheel or had a bearing come apart at some point - a lot of things can happen in 38 years). Anyway, the bearings that came with the car were in good condition and the wheels turned smoothlly. I'm replacing the wheel bearings anyway, but am wondering about the spindles. I expect that spindles are hard to find, so I'm thinking or reusing them. What do you think?"

I should have been more direct with my answer. I would throw the rotors away. They are pretty cheap, even at $50.00 each, compared to a major accident if a rotor were to let go.

Yes, there is no doubt that the rotors will be replaced - new ones on order.

But regarding the scoring, chipping on the spindles. Please see the new thread started on that issue - I'm worried about metal fatigue and a wheel falling off, etc.

I bought 2 rotors from Autozone - 59.99 each. Made in USA. Put a couple of hundred miles on 'em and no problem. Also bought 2 loaded calipers from NAPA for like 42.00 each - also no problems.

Nice thing about buying local is that if you have a problem, you can take them back w/no problems (shipping, return #'s, attitude, etc). For this very reason I'm willing to spend extra dollars at times just to get them from around here.

Sorry, bad ASSumption on my part. Maybe could have answered with part of the question to be clear.

No problem. I should have put a part of the quote in my original reply. graemlins/clonk.gif