Are my rotors *really* damaged?

July 18, 2006 10:26 AM

Our front brakes were making a grinding noise. The shop (which was recommended by neighbors, fwiw) said our rotors were damaged by excessively hard brake pads, and replaced the rotors. They suggested we get the pads changed too. It is making the grinding sound again.

Should I take the car back to this place for pads, or go to my former trusted mechanic (30 miles away, + four hours hanging out)?

(we moved not too long ago).

I am just wondering if I am getting played or not.

posted by craniac to travel & transportation (14 comments total)

The explanation is plausible.

But if the pads were too hard for the rotors, why didn't you replace the pads at the time? If I ran the shop, I wouldn't replace only the rotors if the pads were ruining them. I'd tell you to replace both or neither.

Also, if you took the car to Midas or another chain brake shop for your last brake job, the explanation is super-plausible. I too could sell lifetime brake pads if I made the pads harder than the rotors.
posted by Kwantsar at 10:33 AM on July 18, 2006

Describe the grinding sound and when it happens. I'm assuming it only happens when you're applying the brake pedal - is that correct? Does it seem to get louder/more obvious the harder you're braking? How long ago did you have the pads/rotors replaced by the new shop? Did they have a guarantee/warranty? The parts should definitely have a warranty.
posted by sprocket87 at 10:33 AM on July 18, 2006

Did you replace the pads?

No respectable mechanic would ever replace rotors and not the pads. The rotors rotates with the wheel, and the pads grip them to slow the car down. The two rub together and will develop unique little grooves. When you change the pads, the rotors have to be turned on a lathe to be brought back to flat, or replaced completely. This makes sure that you start with smooth surfaces. If you replace one without the other, you can dramatically affect brake performance because you effectively decrease the surface area between the pads and rotors.
posted by tumble at 10:33 AM on July 18, 2006

The last time I felt a grinding sound in my wheels (driving a Hyundai), it turned out that one of the calipers got stuck.
posted by SeizeTheDay at 10:37 AM on July 18, 2006

When you change the pads, the rotors have to be turned on a lathe to be brought back to flat, or replaced completely.

Wait what? You're saying that every time you replace the pads you have to resurface or replace the rotors? Do you have a cite that supports this claim? No offense, but that claim sounds suspiciously like the "You must change your oil every 3000 miles" scam.
posted by malp at 11:08 AM on July 18, 2006

No, no, malp, you have it backwards.
[P, ~R] Pads can be replaced alone.
[R -> P] If Rotors need replacing, it's usually because the Pads wore through - that's how Rotors get damaged, so Pads need replacing, too.
[P -> (R, ~R)] Just because you replace the Pads, you may or may not have to repair or replace the Rotors.
posted by Sprout the Vulgarian at 11:18 AM on July 18, 2006

Oh, and craniac, it's bizarre that they'd fix the rotors without getting you new pads. The grinding is supposed to be a warning that you need new pads, but usually causes rotors to warp. The whole 'hardness' thing seems weird to me. Take it somewhere different; get a 2nd opinion.
posted by Sprout the Vulgarian at 11:20 AM on July 18, 2006

malp, a through brake job includes resurfacing a rotor, otherwise the brakes may not operate smoothly. i'd never get a brake job from a mechanic that told me that it wasn't necessary.

it's also standard practice to replace the pads when you have new rotors. they have to remove the old ones before they take off the rotor.
posted by lester at 11:20 AM on July 18, 2006

additional info:

• It's our only vehicle, so we needed it back
• They told us to come back in within two weeks for new pads
• It has been about two weeks
• I don't think they're scamming me, but wonder about general competency
• previous pads were put on by the trusted mechanic of yore.
• grinding feeling/sound comes during hard braking, like at the bottom of a hill or freeway offramp.

posted by craniac at 11:54 AM on July 18, 2006

I think that you're getting a lot of anectdotal evidence here. Call "Car Talk" immediately. But seriously folks...
They may have replaced only the rotors for any of the following reasons: thinking you couldn't afford pads; they didn't have the proper pads; the rotors were dangerously thin and needed to be changed immediately; they want to charge you for labor again. They should indeed have replaced the pads, but I would not consider them so disreputable as to avoid a future visit. The grinding sound is not their fault- just get those pads changed asap. Lester: when they replace the rotors, resurfacing doesn't apply.
posted by wzcx at 11:54 AM on July 18, 2006

yes, they were saving us money and suggested changing the pads. I just hadn't heard of "hard pads" causing rotor damage.
posted by craniac at 12:14 PM on July 18, 2006

Second on checking for stuck/sticking calipers. I went through a similar situation a couple times before I found a mechanic that found...and fixed...a caliper that kept sticking and ruining my brakes/rotors.
posted by MrToad at 12:28 PM on July 18, 2006

Senor Toad: thanks, I will look into the caliper problem. I'm half tempted to just learn to do the brakes myself at this point.
posted by craniac at 12:43 PM on July 18, 2006

You are going to think I am crazy:

Try taking off all four wheel covers (hub caps) and see if the noise is still there.

I only mention this because my wife had a noise for months in her wheels that a mechanic chalked up to bad brakes and when another mechanic last Friday on a whim took the wheel covers off, the sound disappeared.

Wheel covers are held on the wheels (at least with the el cheapo OEM covers) with a metal ring held in place by plastic brackets. If one bracket breaks, the ring rubs the wheel and makes a sound like a bad brake.

If I am wrong, at least you are only out of about 15 minutes. If I am right, you can get out of this problem for $30 at AutoZone.

Honestly, I never, ever would have believed this had I not seen it with my own eyes.
posted by 4ster at 9:16 PM on July 18, 2006