2016 Prius with 46k miles - did these rotors need to be replaced?

When my 2016 Prius with 46k miles was in for service, the dealer told me the front brake rotors had heavy rust and needed to be replaced. I agreed to the work and had the dealer leave the old rotors and pads for me.

There are rings of rust around the outer edge and inner edge on the front and back of both rotors. They are not raised, they are flush with the rotor.

I’m curious what others think of the state of the rotors. Would I have been better off keeping these on my car instead of having them replaced?

Edit: 3 of 4 pads measured 6mm, 1 of 4 measured 5mm

Picture attached below:

I would of replaced them.


Yes, they need to be replaced.


Hard to tell for me, but had to do a brake job at 30k for the fronts due to rusted rotors. I got a rumbling of the brakes after a long road trip, anytime else was fine, still get a little rumbling after long road trips, so the rears are probably roast also, but if wife does not notice I will let it go. Tech showed me the outside of the front rotor was bubbled , had CPO so they picked up $180 of $360. 1 year so too late now to get half off.

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I’d replace them.

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Difficult for me to tell by looking at the pics.

However, any brake job should have the rotors either surfaced or replaced. It’s generally more cost effective to replace them than machine them.
There is nothing wrong with machining them as long as the minimum thickness spec is adhered to. It’s a matter of weighing new rotor cost against the cost of machining a used rotor. Varies by facility as to which way they prefer.

Rust is a poor reason for replacing them. The reason for replacing them should involve rotor run out, parallelism, and so on; any of which can cause squealing, vibrations, or brake shudder.
Cast iron can rust overnight.


Brake pads look worn, 3 or 4 mm remaining, how much longer were you planning to use these brake pads?

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The rotors are rusting away because the brakes are rarely used on these cars. Regenerative braking is regularly enough to slow down these cars during normal driving, with brake pads only being used sporadically. I routinely see Priuses go 150-200K miles on original brakes.

How thick are the brake pads in the picture? I see substantial brake pad material remaining there. My opinion, if the brake pads were being replaced the rotors should have been as well. But I would not have recommended brake replacement yet since the pads aren’t worn to 3mm or less.


Isn’t that grove across the pads sort of the same thing as the wear bars on a tire? If it starts to disappear it’s time for new pads. For some reason that has been my thought, but maybe I’m wrong. Again.

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A slot that is ground down into the pad
usually in the center is used to prevent cracking, reduce tangential stiffness, reduce fade, and clean corrosion off the rotor.

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I edited the original post to include the brake pad thickness: 3 of 4 pads measured 6mm, 1 of 4 measured 5mm

Here’s my take on machining versus replacing . . .

I’d rather machine a set of factory rotors . . . provided there’s plenty of meat left after the finish cut . . . versus replacing them with a set of cheap chinese rotors of possibly questionable quality


I don’t see a problem with rust. What I do see is a problem with scoring and generally irregular surfaces of the rotors. Ditto the pads.

If this car was bought new, I’m wondering what your driving/braking habits are. I had a 2007 hybrid Camry which I traded in 2015 and the dealer told me it looked like I hardly ever used the brakes. There was so little wear, I guess they looked virtually new. As I was not all that familiar with regenerative braking, he explained it as the reason why there was so little wear elsewhere.

Good point. OP mentioned minimum pad was 5mm. I’ve read 3mm is time for new pads, so maybe the brake job was premature.