teamking

I was hearing a sound from my right rear (only when the car was warmed up) and happened to be taking the car in to mount new tires and a get new alignment so I asked the guys at the shop to check the wheel bearing.

They said the brake rotor has a hot spot, and not to have it turned but replaced.

I've just gotten the rotor off, and there certainly is a discolored spot.

My question is this: I've heard it said that if you replace one rotor, you should replace the other side as well. Is this true? If so, why?

My theory would be that you might not want your rotors to be a significantly different thickness.

Thoughts?

ahrmike

are you gonna go crazy on the car? cuz if youre not, it shouldnt make a GREAT difference - the hydraulic pressure should pretty much take the path of least resistance - which means it theoretically SHOULD distribute evenly, however there probably will be a bit more 'bite' on the thicker side...

if it were me, i'd change both...whats a 100 bucks for 'knowing' its good. but if youre tight on cash or dont care, it shouldnt be a big deal? (someone correct me if im giving wrong info..)

LostMotion

Measure you other one to see how worn it is. If it's under 0.5mm or more worn I would replace it since you are getting close anyway.

Also you can get the cheapest centric rotors for less than $50 each and they are just as good as the OEM.

savesday04

as ikeyballz said you will probably have more bite on the new rotor and you might pull to that side during hard braking.

mikegarrison

It's OK to just replace the one rotor. Your braking will be a little uneven for a short time, but after that it will be fine.

iam7head

you could, but why?

it's not that much more for one, having 2 different spining masses at each end of the axle doesn't sounds like a perfect fix to me

GRAF-FITI

agree with my long lost HT homie

Greg W

teamking, I agree with mikegarrison. The short-term slight uneven braking is only until the pads bed with the new disc. The difference in unsprung/rotating mass between an old and new disc relative to total unsprung/rotating mass (disc/hub/wheel/tire) is so little that it wouldn't have any effect, even on a track. And doing just one side saves $100, worth a couple dozen decaf mocha frappalotomusses :-)

INTJ

Non-issue. I bet your tires (and balancing weights) weight different amounts as well.

mikegarrison

BTW, it's not just theory. I routinely replace just one rotor when I'm at the track.

It's a little different from your situation, because the failure mode on the track is cracking. But unless the other rotor is obviously also about to need replacing, I'll just do the one.

So basically, the decision comes down to whether you think the other rotor is still good, or whether you think it is just about to fail. If it's still good, might as well keep using it. If it's just about to fail, might as well swap it while you have the car up on jack stands and the tools out anyway.