Brakes - rear rotor rust - Page 2 - Kia Niro Forum
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post #11 of 14 (permalink) Old 05-09-2019, 04:37 PM
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And I also know from my own experience and talking with a rare commodity (an honest auto mechanic). Pitting and re-surfacing of your rotors is a total sham. The net effect on your braking performance is negligible and you are doing it for cosmetic purposes. The pitting that is on the rotors can slightly reduce the surface area for the brake pad to contact, but the metal rotor also wears away in use so any pitting general is removed by wear over the course of 4-5 good stops. But the removal (re-facing) of your rotors removes more material that greatly reduces the life of the rotors as well as their ability to dissipate heat also will reduce the stopping distance. along with the brake pads don't always wear totally even, so as they wear they bed to the rotor so the two surfaces are matched to each other. As you resurface the rotor, then it will have a different matched surface to that of the pad, so you will also lose far more stopping distance as the brakes re-bed. So when you add up all the pros vs cons, it turns out far better to just leave the brakes alone and just stop a bit harder to let the pad ware away the metal rotor to a more clean finish.

But these are Hybrid vehicles and if you read the other thread about one pedal driving, you'd see that we don't really use the rotors all that much so I don't know why anyone would really be all that worried about rust or how pitted they are as the stopping power of the rotor is likely multiple times more than what is ever needed to stop.

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post #12 of 14 (permalink) Old 05-09-2019, 07:59 PM
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Originally Posted by Amyga View Post
This is an old thread, but I just had my first maintenance at the dealer, ~7,500 miles after 10 months, and they found that rear rotors were pitted and would eventually need to be resurfaced.
The car typically stays put in the driveway four consecutive 4 days, then I use for 3 days. That gives ample time for any rust to form and to start digging apparently.
I am just writing in case it's useful information to someone else.
I would steer clear of anyone who suggested resurfacing rotors. Surface rust will be cleaned off as soon as you hit the brakes and any pitting is likely to be so minor as to not impact performance at all. All resurfacing does is remove material, making the rotors less able to absorb and dissipate heat, leading to more wear and premature failure. Factory rotors are $85 new, which is probably not a lot more than they would charge to turn your old ones.

The rotors will take forever to be significantly harmed by surface rust. Once the surface oxidizes the process slows down dramatically as the layer of rust actually protects the surface underneath. Even driving occasionally as you do you should see good service life from the brakes.

I come from VWs which generally treat rotors as wear items and recommend replacement with the pads. The rear pads on my Golf last several years, so an extra $100 for new rotors is cheap insurance.
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post #13 of 14 (permalink) Old 05-12-2019, 02:32 PM
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If just the rears, you can use the parking brake for a final stop from slow speeds as well. Kind of interesting to see how "well" they stop too.
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post #14 of 14 (permalink) Old 05-12-2019, 06:49 PM
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My Corvette rotors rust after sitting for a week, depending on the weather and it's gone as soon as I hit the brakes.
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