Thanks for your reply.
There are enough miles on the car that the front brakes may have been serviced once. It's a used car, with incomplete repair history. In my experience, it's unusual for cars to need brakes on both ends at the same time.
My Toyota Dealer told me I'd be needing brakes soon, and gave a quote that included both rotors and pads. I prodded a bit about the rotors, and they said they always replace both. This will almost certainly be the car's first rear brake service, so I'm skeptical that the rotors will genuinely need to be replaced. It seems factory parts are also rather expensive.
I'm a mechanic by trade - though haven't serviced cars for a living since 1980. Been mechanicking other stuff since then. At any rate, the high quote I got from them has me thinking about doing the work myself, or using an independent shop. My experience when I *did* work on cars is that there can be substantial differences in the quality of third party replacement parts. I'm left wondering whose stuff is good quality, and whose is not so good.
