Brake grinding at low speed

[mixedpixel]

I picked up my Volt two weeks ago, and I have been having a lot of fun driving it. I do have one issue with the brakes that I am trying to figure out. As I step on the brake pedal and slow to very low speed, there is a 1 or 2 second grinding as the car comes to a stop. The grinding seems to be both audible and transmitted through the brake pedal. It's a very odd transition - smooth, grind, and then the last little bit to a complete stop is smooth again.
I took my Volt into the dealer this morning, and the person who drove it said it was probably the regenerative braking. I'm not buying it. Has anyone else experienced this and figured out what it is?

[Stilgar99]

Doesnt sound right. I have no 'grinding' in mine.

Stilgar

[Henry_FL]

Your hearing the transition from regenerative braking to friction braking ...

If you rarely use the full braking ( I've learned to one pedal drive with using low ), the brake can have all sorts of crud on them and get cleaned only when you come to a full stop.

Trying a couple of 30-0 stops with hard braking, if after that you still have a grind, you brakes should be checked by the dealer.

[DCFusor]

Some people are also fooled by the running of the hydraulic pump, which you can feel slightly in the pedal. But yes, this is also one of two vehicles I have that tend to have rough discs due to little use, and that first stop is grabby and rough.

[Empire]

I have experienced the same thing although not as dramatically as you describe. My brakes will squeal when the disc brakes are applied as I nearly come to a stop. Quite annoying as my $42,000 car sounds like an old clunker when I pull in my driveway. I've gotten good at using the regen braking almost exclusively so I will try, as Henry suggested, a couple of hard stops to clean up the discs and see what happens.

The feeling in pedal is just a feature of the braking system and one valid criticism of the Volt in that the transition from regen to hydraulics can result in a suddenly more aggressive stop. Just takes some getting used to, especially going into a hard corner.

That's not a knock, believe me. I love my Volt.

[dwl]

What he is describing sounds very similar to what I experienced in a loaner Volt. A definite grinding sensation for a second or two while braking at low speeds. Something that my Volt does NOT do. It persisted very consistently through my entire 2 days of driving it. I don't recall if I really slammed on the brakes at any point, though. So it could have been rust that I was just doing a bad job of knocking off. But I get the impression that this loaner sees a fair bit of use. So I'm not sure.

I think Henry's suggestion is a good one. Work the brakes pretty hard for a day or so. If it doesn't go away, it's a problem that needs to be looked at for sure.

[solar_dave]

Drive it in D for a day or 2 and be a bit more aggressive on the brakes, if it is just a break in issue it should go away.

[Codyozz]

I agree with all the suggestions above. New brakes can often have a break in period where things don't quite line up yet. Also, when there is rust and such on the brakes they don't sound very good. Yes, do some hard stops and get some actual pressure between the pads and the discs. I have one warning with this: do not overheat the brakes with continued long use such as going down a long steep hill. This will not only wear in the brakes but over heat them and warp them.
The forum suggests quick jabs at the brakes of no longer than 5 seconds, which will NOT overheat them. You do not want to overwork them in a short period with long pressure & time as to over heat them.
I think you get my point, it's a pretty simple process and I'm sure you've seen warped discs before. I just know I've seen a few uninformed who think "all cars brakes shudder when they get old". NO! You just ride the brakes and screw them up!!

Lastly, do me a favor. When your car is cold (hasn't been driven in at least an hour) reach in the wheel and rub the brake disc with your finger and see if you can feel any ridges or rust build up along the disc. If it feels really smooth, you may have a different problem.... Also, with the car in your drive way... have someone squat outside the car as your car idle creeps (2mph) and have them listen from the outside as you apply pressure to brake pedal. If they can plainly hear noises you then might do the hard brake testing suggested above.

[mixedpixel]

Thanks everyone for your suggestions. The mechanic at the dealer said there were two sounds I could be hearing, the hydraulic pump and the sound of a gear engaging. I know it's not the first and I don't understand the second, but they offered to let me compare with another Volt next time they have one available.

[saghost]

Drive it in D for a day or 2 and be a bit more aggressive on the brakes, if it is just a break in issue it should go away.

D won't make the slightest difference - it'll do just as much regening, with different pedal positions. If he's aggressive on the brakes, that'll help - or if you want to make sure the car uses the rotors every time, drive with two feet and leave the accelerator slightly depressed - that stops the car from doing any regen at all.