drvai

Hi all.

We got the first heavy snow fall in Chicago. The S5 (with Dunlops 4D wintersports) drives awesome. But I noticed that when the ESP or ABS goes off while driving in 2-3 inches os snow, there is "harsh" noise coming from (at least) the front wheels. Kind of a "scartch". This does not happen when the ABS goes off in pavement (or slight snow).

Is this snow between the caliper and the disc? When I got home, I checked the brake discs and they are not damaged or scratch.

any thoughts?

bilbo47

Many years ago I broke my pick-up truck so bad I had a rental for a couple of weeks, and the rental was a Ford Taurus or something like that. It didn't have winters, and that was the first time I had experienced ABS that sounded and felt like someone put gravel in the disc brakes.

I don't normally trip my ABS in the dry or wet, and rarely in the snow, but earlier this year I heard the same sound. I assumed it was normal, having remembered the same type of thing in the Ford.

I expect it to happen this AM. I just dug out, and in a little bit I'm going to try my commute. :P

That's all I got, hope it helps.

Nastybutler

That sound is the brakes doing their thing. Mine makes that sound, but without hearing exactly how loud your is compared to mine it's hard to know if yours is out of whack.

drvai

But doesn't make the noise when braking (and no ABS going off) or braking hard (and ABS going off) in pavement with no snow.

lyleswk

I would expect no noise in the dry...ever. Unlike early ABS systems that "cycled" a lot, newer ABSs are so good that I have never noticed the system cycling the brakes including when I put my foot to the floor at 45 mph just before totaling a Mercedes GLK on the side of a 3/4 ton Chevy truck. I also noticed there were no skid marks indicative of cycling brakes!



I have noticed ABS cycling in the wet a couple times on my A4 that may sound like the "scratch" you describe. But, this is so infrequent, that you may never have noticed it.

As far as ABS operation on the snow, I have noticed in my very limited driving in the snow (I live in Texas), that when the ABS does cycle, it is at a different frequency due to the very low coefficient of friction and that combined with the noise of the tire on the snow is much more noticeable, but always wrote it off as normal in snowy conditions.

irenesbob

I have noticed that there is only such a noise when the snow is of the dry, crystalline variety and temps are really cold. On slushy, wet snow and warmer temps, not so much. I think it is the sound of the friction of the rubber scraping along on the firm abrasive crystalline snow.

drvai

Thank you all for response. I usually really avoid taking the car to the dealership but I have my 5,000 mile service coming up anyways and will ask them. To be honest, they will likely say they checked "and everything is ok" or "is normal"... which may or may not be true.

bilbo47

Duh (forehead slap). Yup, I totally agree. The grinding sound isn't the brakes, it's the tires!