Brakes grinding noise in wet weather.

This noise starts to happen in wet weather. It goes away again when the brakes dry out. I can’t observe any correlation with the make/model/year of the car, the age of the car, or the condition of the brakes. I have noticed it over the years on a wide variety of makes and models, domestic and foreign. Old beaters and brand new cars off the showroom floor. Once when I heard brakes making this grinding I took the car into a shop to get the brakes looked at. They told me there was nothing wrong with the brakes.

What’s the Straight Dope on this wet-weather brake noise?

Maybe you live in an area with particularly coarse rain. :slight_smile:

A lot of cars have a tendency to make brake-grinding noises for the first few stops after they’ve been parked in the rain or mist. It’s because brake discs rapidly get a very light coating of rust from the moisture. (They can rust in a few seconds under the right conditions.) Using the brakes scrapes the rotors clean again, and the noise goes away pretty fast.

All (3) of the cars I’ve had did this. If you’re talking about a sound that lasts longer than the first 3-5 stops, then it’s probably something else, I don’t know what.

Your brake rotors can rust very quickly. They can make a grinding noise when you first drive your car after the rotors get wet, but it will go away after the rust gets scraped off by the brake pads.


Is it really an unhealthy ‘grinding’ noise, or something else? Anti-lock brakes when they’re working properly can make a funny shuddering sound, and if I remember correctly they’re more likely to do that when wet. If you didn’t know what it was, it might sound alarming. (I don’t drive, but I’m trying to remember my mother’s car, which is a 2001 Pontiac Sunfire.)

The new ridiculously expensive Maybach senses moisture and automatically applies the brakes just enough to keep the rotors dry while driving.

ABS - Anti Lock Breaking System, gotta be.

My old car made a terrible grinding noise when the ABS kicked in. I asked at the garage and they said it was supposed to sound like that.

Does your car have ABS ?

If so, you will get that noise on loose gravel or snow/ice surfaces as well.

I agree with Lagged2Death and Joey G. If you read the OP, many of the cars mentioned could not have had ABS (which stands for Anti-Blockier-System, by the way). ABS operation is accompanied by vibration in the pedal, and the sound is not described as grinding by most people.

There was one winter where I got actual road grit (spread liberally on icy roads to give traction) inside my brake drums, and the horrible grinding noise, and grinding feel, was unmistakable. I had to have them replaced because the grinding grit had wrecked them. The mild grinding noise caused by moisture is small change by comparison. You guys are right; after the first 4 or 5 brake applications it goes away. Thanks for explaining the phenomenon to my satisfaction.