I recently had a tuneup on my car and the brake pads were at 8mm. Is this getting close to “replacement time”?
Also some of the online forums reccommended replacement pads for my (sports)car and also suggested to spend the extra $50 to change rotors with no real reason. Any sense in swaping 20k rotors for new ones?
Part of this is legally driven, part mechanical.
If you have a vehicle which is a classic, antique, or otherwise mileage restricted, then there is no good reason to replace brake components until they are worn to the limit of their useful life.
For daily transportation, safety inspection limits apply, which vary from state to state.
Brake pads wear at a rate which is a function of your driving style. Stop and go, in town drivers will wear pads more quickly than the turnpike traveler. The rotors also wear, but to a lesser degree. Just the same, they should be turned when pads are replaced to eliminate surface irregularities and ‘runout’ or lack of linear trueness. When rotors become too badly worn, they must be replaced, as they cannot properly dissipate heat and are unsafe. All rotors have a minimum thickness, and a garage technician will advise you if this limit is near.
Not knowing the details of your vehicle, I cannot confirm or deny the accuracy of the claim, but I hope you have a better understanding, now.
No. It’s probably not more than half worn.
Probably not. If they’re significantly scored or warped, they should be resurfaced or replaced. It’s very unusual for rotors to have problems at that mileage. “Official” recommendations vary, typically auto manufacturers say don’t service the rotors unless there’s a specific problem, brake pad manufacturers say to always resurface or replace them for optimal performance. Each has its own agenda, minimizing warranty costs and minimizing the likelihood of noise, respectively.
Replace the rotors? Maybe. Here’s the deal:
Use to be that rotors were designed to last much longer than the brake pads themselves, even if they were turned to restore their nice parallel surfaces. However, when manufacturers changed over to semi-metallic brake linings, they noticed that in addition to their increased lifespan and fade-resistance, they tended to be noisy in ways that irritated owners. So, to eliminate the noise, they started making rotors out of softer cast iron. Problem: the rotors wore faster. In the end, some manufacturers decided to make the rotors thinner so that the rotors now lasted as long as one set of pads. This might sound stingy, but I think it saves trouble and labor costs in the end.
Art
I’ll “ditto” what Art said and add this: Let’s say your rotors are just fine. You add brake pads and drive away. Here’s the problem: even rotors that are fine have grooves in them. When you change brake pads, for the first dozen or so stops, you don’t have a good seat for the brakes to bite. This will work itself out and the braking power will be normal once the pads set up with the rotors. The real downside: expect lots of squealing/squeaking for the life of the new pads - enough to make alot of drivers head right back to the shop. Not just at break-in, but for a long time.
Let’s say you want to have the rotors machined tom smooth them out. Ok - pretty good idea. It is a good idea, but there is a very good chance the rotors are not thick enough to machine. Even with 20k they might be too thin. I believe VW is one car where the rotors can never be machined, even after just 20 thousand measely miles. It’s not just VW, but they are an example.
There are many premium quality brake pads designed to be noise free. In the last couple years, I’ve done quite a few pad-only brake jobs in cases where the rotors were in good shape, using such pads. No noise.
Even new or resurfaced rotors require some break-in. It’s not just a matter of surface flatness and smoothness. Some of the pad material imbeds into the rotor surfaces, and until this occurs braking performance is not yet 100%. In this regard, used, non-resurfaced rotors are already broken in.