Brake Advice - Do pads have to be replaced when new rotors are put on?

Tiny
PHILLIL60
  • MEMBER
  • 2012 AUDI Q5
  • 3.2L
  • 6 CYL
  • AWD
  • AUTOMATIC
  • 46,000 MILES
I bought this used Audi from a Subaru dealer. It was clear the rotors were shot, so they agreed to "Fix the Brakes". They determined the rotors were all warped and beyond repair and then replaced all four rotors.

After I picked up the car, I took it to get new tires and they said "did you realize they put new rotors on without replacing the brake pad. That is simply not done. If you have warped rotors, that means your brake pads are bad, regardless of the wear remaining." The front brakes have 4mil and the back have 5mil.

I took it to an Audi dealer on an unrelated issue, and they pointed out the same thing and told me the old brake pads have now done damage to the new rotors. Not irreparable, but they've started creating grooves.

My question to you is, did they do the right thing by not replacing the brake pads along with the rotors, regardless of the wear left on them. They say "everyone I've talked to is just trying to sell me something" and won't take me seriously and they did nothing wrong since there was still life left in the pad (which I understand isn't really the point anyway). I'm hoping a non-invested third party expert may convince them. Thanks for your time and attention.
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Friday, July 11th, 2014 AT 1:46 PM

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Tiny
CARADIODOC
  • EXPERT
You've been given some misinformation, but not necessarily in an attempt to defraud or deceive. First of all, " If you have warped rotors, that means your brake pads are bad" is absolutely not true. What I suspect they were referring to is the microscopic grooves worn into the old rotors, and the matching grooves in the linings. The exact same thing happens to a lesser degree when any new pad is installed with any new or machined rotor. In both cases it is customary to drive carefully during the first hundred miles or so until the parts wear to match each other. The same thing will take place with your old pads. They'll wear to match the rotors very quickly. On the test drive after a brake job, we will perform a few fairly hard stops, with brief cooling periods in between, to "seat" the pads. There was one instance where I didn't do that, and with new pads AND new rotors, the customer experienced severe brake fade within the first few minutes of hard city driving. Because the pads weren't worn to match the rotors yet, there was less material making contact so what was built up much more heat. The fix was to let the car sit for a couple of hours, then go and drive it. By that time the brake fade never occurred again. The owner's hard driving did what I was supposed to have done on the test drive.

Second, there have been plenty of instances where brand new cars develop warped brake rotors within the first few months. It has nothing to do with their quality, and definitely not worn or defective pads, as the second mechanic said. Chinese rotors in particular have this problem, but more so with replacement rotors, not original equipment rotors. When they make a rotor, they cast it, machine it, then ship it. When we make cast iron parts, we let them "age" for 90 days before they get the final machining. Chinese rotors age on your car, and they often warp in a few months. Your new ones could too. All that is needed is a light machining and they'll be fine after that. Demanding the auto parts store replace them under their warranty isn't the right solution because the next ones will do the same thing. Here again, that has nothing to do with the pads. In fact, it could be what happened to your old rotors.

The argument can be made that my last assertion is wrong too. There's two legitimate reasons to replace rotors rather than machine them regardless if you're paying for a normal brake job or the dealer is doing it under their warranty. The first is when they're worn beyond the published legal limit or will be after they're machined. Professionals know doing that can make them a defendant in a lawsuit after a crash when the OTHER guy was at fault. The second reason is simply a matter of dollars. Maintenance of the brake lathe and the high cost of the cutting bits that wear out quickly means they have to include those costs in the cost of the brake work. Then there's the labor time they have to charge you for. It is actually less expensive for you to install new rotors rather than machine what you have and end up with old ones that may need to be replaced at the next brake job anyway. This could also be why your dealer put new rotors on instead of machining the old ones. Less cost and less time for them, and you get better parts. You both win. This also suggests you're involved with a dealer that puts their customers' best interest first, which most do. Short-sighted service managers tend to push the machining when it's warranty work they're paying for because they can show that they fixed your car for a lower cost to the dealership. The cost of maintaining the brake lathe falls under "shop maintenance" and reflects less on their ability to control costs to the dealership.

The case can be made for the second mechanic's comments too. I suspect he didn't know why the rotors were replaced, just that they were. You didn't say what the symptom was, but when you mentioned "warped" I assume there was a pulsation in the brake pedal or a shimmy in the steering wheel when braking. Those symptoms have nothing to with the pads. In fact, brand new pads would do nothing to change those symptoms. Without knowing the symptom, most mechanics would assume the rotors were ground down from metal-on-metal contact when a pad wore out completely. That's when you come in with grinding noises, and by that time it's too late and there's way too much wear to the rotor to save it. It is already under the published minimum legal thickness. The appropriate repair then is to install new pads and new rotors.

Also beware of "the other guy is wrong, and only I can be right" syndrome. Some mechanics try to improve their image by cutting their competitors down. That rarely works. Mechanics typically DO have very poor communication skills, but they should be able to explain to you in terms you can understand, the reason WHY a part is causing a problem or why it needs to be replaced.

As for "They say "everyone I've talked to is just trying to sell me something", there are some shops that go overboard in that respect because their mechanics work on commission for the extra parts they sell you. I don't know if that happens at new and used car dealerships, but it is real common at the national franchise brake and exhaust shops. When I worked for a real nice family-owned Chrysler dealership, we were often asked to provide second opinions after the owner went to the chain shop across the road. We commonly turned their $600.00 estimate into a $250.00 repair.

In this case, when neither the pads nor the rotors caused damage to the other one, to determine which parts need to be replaced, each one should be inspected and evaluated on its own merits. While it is customary to replace both during a regular brake job, this wasn't a regular brake job.
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Friday, July 11th, 2014 AT 6:59 PM

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