Replacing only one rotor--good idea or bad idea?

Brentmc · Aug 1, 2007

I am fixing the 4-piston front disc brakes on the 67. The driver's side rotor was turned and is ready to be installed. The passenger side rotor can't be resurfaced again (not thick enough) and was covered with brake fluid/minor surface rust that I have cleaned off. I would like to be able to reinstall it and use it with the resurfaced driver's side rotor.

That said, I've read that it is recommended that rotors be replaced in pairs so that the surfaces are identical and the pads grab evenly. If this is accurate, then I have no option but to buy two new matched rotors.

Otherwise, I've read, one side may grab more than the other and cause a pull to one side. That would even rule out using the resurfaced rotor with a brand new rotor on the other side. I don't know if all of this is just marketing from the manufacturers of the rotors or the truth.

What do you all advise? Any reason you can see why I can't install both of these rotors "as is" and just use them? I'd think that unless one had a lot more friction than the other, there wouldn't be that much of a difference in the two...ultimately won't the pads grab evenly...especially once they grind on the rotor a few hundred revolutions?

JimM · Aug 1, 2007

While I have heard that too (replace rotors in pairs) I don't buy into it, and would replace only the bad one.

My reasoning is that the caliper pistons are able and expected to "adjust" their position in repsonse to both rotor and pad wear. The thickness difference between "new pads & new rotors" and "near worn out pads and rotors that have been cut to the limit" is a good 1/2 INCH!

I don't think it would be an issue, and have personally replaced only 1 rotor more than once without a problem.

BPOS · Aug 1, 2007

I agree with Jim. Just make sure that the rotor you can't resurface still meets the min thickness that is stamped on it. When you use a rotor that is not thick enough you run the risk of the piston in the caliper coming too far out and losing its sealing ability. That would be a train wreck.

67FamilyFun · Aug 1, 2007

Is the stamped number the min thickness that it would get machined too, or a minimum thickness to be used safely?

67FamilyFun · Aug 1, 2007

Seems you have nothing to lose trying except time. So if the bad rotor is worn past the minimum "machining" specification, but if it isn't past the "discard" specification...wouldn't hurt to try. (I have no idea what those dimensions are or that is what they are really called, but if I designed brake rotors, that is how I would do it...)
My only concern would be how many miles of wear are left on the bad rotor until where you would have to be concerned about a catastrophic failure of the rotor if it is too thin.
I've read about people just scuffing up the surface with a scotchbrite so the new pads will bed in properly...
Scott

davidpozzi · Aug 1, 2007

The rotors say "Min Thk XXX" I take it to mean that whenever the thickness drops below that number, the rotor should not be used. I don't take it as a minimum that the rotor should be machined to.

If the passenger side rotor is not below min thickness now, I'd try it and see how the brakes work. You can always replace later it if the brakes are unbalanced.
David

wiskeesour · Aug 1, 2007

davidpozzi said:
The rotors say "Min Thk XXX" I take it to mean that whenever the thickness drops below that number, the rotor should not be used. I don't take it as a minimum that the rotor should be machined to.

If the passenger side rotor is not below min thickness now, I'd try it and see how the brakes work. You can always replace later it if the brakes are unbalanced.
David

Ditto

Brentmc · Aug 1, 2007

Thanks again guys. I will have the rotor mic'd and put it on.

Chuck · Aug 2, 2007

One other thing to consider. A rotor that is at or near min. thickness has a much greater chance of warping. Not necessarily dangerous, but quite annoying to have that brake 'n shake feeling.

BonzoHansen · Aug 2, 2007

Didn't we just have this conversation? I've got this weird deja vu thing going. LOL

Hydrulics in pairs. I don't ever remember having an issue with replacing one rotor when the other one was w/i tolerance after machining. Change the one and go from there.

davidpozzi · Aug 2, 2007

I would expect the new rotor to have different friction than a used rotor, but hopefully when broken in, it would even out with the other side.

Replacing only one rotor--good idea or bad idea?

Top Contributors this Month

Recommended Communities