It’s been a number of years since I installed new brake pads on a car as a do-it-yourselfer, and I always just used new pads and didn’t do anything with the rotors. I just had a safety inspection, and they told me the brakes just barely passed - the pads were getting thin. They said a brake job would include new pads and new rotors. Later I took off a wheel, and the rotors looked fine to me. Since I’m kind of past my DIY days, I’m wondering if they really need to replace the rotors and could just install new pads?
They should at least be resurfaced because any rotor will wear unevenly even if you cannot see it with the naked eye. What I’ve noticed is they are often too thin to be resurfaced so in that case, yes you need new rotors.
Here’s a page on it.
If a Rotor needs resurfacing it should be replaced. If it looks fine and your pads wore out normally no reason to do anything to them. Any slight wear will quickly seat in.
The rotors have a certain thickness they must meet in order to meet specification. This is probably cast or stamped into the rotor itself.
I’ve done dozens of brake jobs. If the rotors are pitted, grooved, scored, rusty, etc., simply replace them. They’re cheap nowadays.
(And if they look O.K., you should also measure their thickness and do a runout measurement. But I suspect most shade tree mechanics don’t bother with it.)
I almost always did.
The alternative is a trip to a mechanic or parts shop with a rotor lathe. I’d rather do the job start-to-finish with all new parts than dragging partially used expendables across town to maybe buy new replacements anyway (because they can’t turn my old rotors for a variety of reasons).
I buy new rotors because the cost saving nowadays over resurfacing is negligable. Is there any scenario where you wouldn’t replace the rotors on a brake job?
Some cars have rotors that need to be replaced along with the brake pads. BMWs are one example. I’ve heard they use softer metal in the rotors for better stopping performance. This means they wear out sooner. Even if the rotor thickness is still in specs when the pads are changed, they won’t stay in specs through the 2nd pads. So in cars like these, the rotors and brake pads are almost always changed together.
Maybe every third brake job. Pads every 20k, rotors every 60k? (I’m guessing the mileage based on past experience, not as a rule.)
Back in Ye Dayes of Yore, it was common for rotors to be made with lots of extra metal on them so they could be resurfaced multiple times before being too thin and needing to be replaced.
Somebody at Corporate got a bonus for realizing that extra metal wasn’t benefitting the car company’s bottom line; rather the opposite. Rotors are now made thinner. Works for them
The point of this colorful story is that experience from working on 1970s or 1980s American cars isn’t relevant if the OP is dealing with a newer car and/or from a different manufacturer. In fact … year, make, model, and trim level of the OP’s car would go a long way to enabling us to provide an actual factual answer instead of the mostly IMHO answers we’ve been providing.
Thinner rotors aren’t cheaper, they are more expensive. But they reduce unsprung and overall weight, and new rotors are safer because warping may not be noticable. Replacing rotors generally isn’t going to benefit manufacturers because most people have their brake jobs done at independent oil and brake shops which will typically use aftermarket parts.