Brake grinding noise. Why do my rotors look like this?

Your picture didn’t come through but your discription leaves little doubt that the brake pads have worn down to the metal backing.

 

Hard to say without a picture. Can you try again.

Just guessing, though, without knowing more about the sound, every Prius I've had has made a grinding noise when first applying the brakes after sitting overnight. It's humid here in FL and they flash rust while just sitting.

They could also be worn out, but at only 130,000 miles that implies lots of late, hard braking. I just checked my wife's brakes on her 129k mile '07 and there's still 6-7 mm left on those front pads. They should go at least another 130k.

 

An entirely different take than I had from his post.
Sounds like pitted rotors to me.

Often caused by only a little use and exposure to water and winter road chemicals.
It really isn't a problem.......except the pads will wear considerably faster.......and your grinding noise might indeed be worn out pads.

 

take them apart, clean and lube, measure the pad and rotor thickness and replace anything that is below factory spec.
rotors may just be rusty which isn't a problem, and typical for prius

 

Waiting for pics. Also, how often have you had a full service on the brakes? Ever? Toyota USA recommends tri-yearly or 30K miles, whichever comes first.

Meanwhile, some light reading:

 

Found the image, just rust, good time to lube the pins, check the pads.
The rotors can be turned, but just using the brakes will shine them right up.

 

How/where did you find the image, sure it's the OP's? I'm not sure that's rust, looks almost like some sort of glazing, with bare patches??

Yes. I had seriously knackered rear brakes. About 6 months prior I did the rears, and completely neglected the caliper piston orientation requirement. As a result, the caliper piston was pressing on only a raised pin on the back of the inner pad, and the pad pressure against the rotor was completely skewed.

The inner face of the rotor was about 50% rusted up, due to lack of contact. I removed the rotors, scoured them with steel wool, reinstalled everything (properly this time), and thought I was out-of-the-woods.

But the first time I drove, it sounded horrible. An hour later, not so bad. A day or two later, had to listen hard. a week or two, completely back to normal: rotors looked uniform shiny.

 

Those pitted areas look at least a couple thousandths deep. I've rarely seen anything like it.

I would take a micrometer to it across the thinnest spots (deepest pitted patches) and figure out how close it would be to minimum thickness after turning.

Is it like that on both sides? If there's a place with deep pits on both sides lined up with each other, that's an easy measurement ... otherwise it's a bit of a math exercise: measure the "unpitted" thickness at some spot where there's no pit on either side; measure at some spot where one side's pitted and the other side's good; subtract to get the depth of that pit; same for a spot where the other side's pitted and the first side's good; subtract both pit depths from the unpitted width to get an idea where you'll be after turning.

 

That picture looks like corrosion. Salt perhaps. When I wash my car and let it set you can almost sit there and watch the rotors turn red with surface rust. They sound like metal to metal after the first brake application. I can just imagine what the rotors look like after sitting a week or so after they’ve been subjected to road salt. The Toyota rotors are basically low grade pig iron and are very susceptible to the elements.

 

if that is the o/p's pic, replace the rotors

 

my daughter and i have put almost 300,000 cumulative miles on three different pri, from vermont to mass, and i've never seen rotors that looked like that. the area under the pads is always smooth and shiny.
those look defective or something

 

I suspect it'll take more than some hard stops or brake cleaner to fix those. A brake lathe ... now that might just do it. If the micrometer shows the minimum thickness is still enough to get away with it.

 

Those look like voids in the casting, but I know they almost certainly would not have made it onto your car in the factory like that or past your eyes when you lubed the pins.

 

That's easy for you to SAY. Would you actually do that yourself on your own car ??
Somehow I think not.

 

why do you say that? i would take it to a mechanic and have it done.

 

I've got the dial indicator (with magnetic base), and micrometer, and the Repair Manual specs. I try to check out the rotors at least one time. They're rarely anywhere significantly lower than new thickness, but the runout can get a bit iffy. I just carry on. It takes me longer to fold the magnetic base so it fits back in it's case than to do the measurement, lol. But I always insist on doing that, my cross to bear, har har.

 

You mean, look in the manual for the specs, measure things, and replace them if they need replacing, as directed by the manual?

It's what I do. You didn't explain why you "think not."

 

But that is NOT what you said.