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M2 Technical Topics > Suspension | Brakes | Chassis > Has anyone with an M2C had their brake pads seize to the rotors from road salt?

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      02-21-2020, 12:36 PM   #1
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Has anyone with an M2C had their brake pads seize to the rotors from road salt?

I live in the Pacific Northwest, so the winters are pretty mild, but wet. I have winter tires on my car and drive it daily. I don't have a garage to store her in though unfortunately.

A couple of weeks ago, we got some snow and they had salted the roads. After driving, I parked the car, and ended up not driving it for like 5 days. When I went to drive off, the car would not budge! The front brake pads had seized onto the rotors!

It was like having a line lock kit - I actually sat there spinning my rear tires a bit and the car would not budge. After trying that a few times, it broke loose finally, but upon braking, it was vibrating like crazy (you could feel it in the car, even as a passenger).

I took it in to the dealer, and was surprised to hear that is not considered a defect of any kind, and pretty much nothing with the M2 brakes is covered under warranty. My car only has 10,000 miles on it. I can understand if they think you have been taking the car to the track, or it is a wear and tear issue, that it would not be warrantied. But how can they claim it's normal what had happened?

I wonder how anyone else who parks their car outside in the rest of Canada which sees salt all winter or in the Northern parts of the US deals with this issue? I've not found any others who have experienced this.


So I decided to try to bed them in again, and did 10 hard stops from 60 to 10 MPH, cooled down, then repeated, and fortunately most of the vibration is gone, but it is still there a little bit on the highway.

Here's pictures of the front rotors now. Is the leftover rust going to eventually go away do you think? Will it cause issues down the road? Should I try to maybe sand it off myself, and if so, using which grit?

.
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      02-21-2020, 12:45 PM   #2
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This is very common, the number one cause of brake vibration with BMWs.
Often requires rotor machining or replacement to eliminate vibration.
I've had it happen just from washing and parking without drying, road salt is a catalyst too and high temperatures ie tracking can do as well.
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      02-21-2020, 12:54 PM   #3
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Quote:
Originally Posted by Acetech View Post
high temperatures ie tracking can do as well.
Can confirm.
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      02-21-2020, 01:11 PM   #4
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Mine stick slightly the morning after a wash, but never had it this bad.
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      02-21-2020, 01:39 PM   #5
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I usually wash on Saturday and don't move the car until Monday morning so it typically sticks a tiny bit. I started using P&S Brake Buster as a wheel cleaner; people have said it has corrosion inhibitors that help keep the brake rotors from rusting after rinsing. Visually I think it works a little bit. I can't say if it helps keep the pads from seizing.
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      02-22-2020, 03:10 AM   #6
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I've had the parking brake pads stick, but that took a couple of days of being stationary after driving on salted roads.

Last edited by M Fifty; 02-22-2020 at 04:09 PM.. Reason: Speelunk
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      02-22-2020, 11:47 AM   #7
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Confirm this can happen occasionally on The smaller brakes for the OG as well. I just rev it up until it releases with a loud pop. I park indoors so everything dries out and I assume rust sticks the pads. It hasn’t happened with my ferodo pads just with the stock M pads.
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      02-24-2020, 09:37 AM   #8
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As others have noted, this type of pad deposit can happen in several ways. In your case, the pads got wet, and essentially rusted to your discs. We see something similar when people track their cars and park with the parking brake. The pad material melts onto the searing hot disc face. In either case, the fused pad material creates a high spot on the disc. Every time that high spot comes around to the caliper while you're squeezing the brakes, the pads register that high spot as a little hump...giving you a pedal pulse.

When you did the ten 60-0mph stops, you probably start to peel off the high spots. If you got the pads hot enough though, you may have started to lay pad material down on top of those high spots, which could exacerbate the problem.

You need to scrape the discs cold. You don't want to heat them up and lay more material down on them until those high spots are removed.

There are a couple potential solutions.

Do you have a set of race/track pads? The compound in a track pad is more aggressive/abrasive. It will do a better job of scraping the discs vs. a road pad. If you install your race pads and drive them around a bit cold, they will act as a brake lathe and scrap off some of that pad material that fused to the disc. That is one option.

Another option is to take a red Scotch-brite pad and scrub those high spots. Scrub them side-to-side. You may find that you can remove much of the pad material in this manner.

A long time ago we did a video on swapping between street and track pads that is relevant to this topic. Once you understand what is going on with the pad material and how it interacts with the discs, then it becomes easier to find a solution. In this video I was 'scrubbing' the discs in my old C5Z06. You can watch the pad material peel right off the disc in real-time:

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      02-24-2020, 11:40 AM   #9
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Thanks. Great reply. I'll reply within yours in bold.

Quote:
Originally Posted by jritt@essex View Post
As others have noted, this type of pad deposit can happen in several ways. In your case, the pads got wet, and essentially rusted to your discs. We see something similar when people track their cars and park with the parking brake. The pad material melts onto the searing hot disc face. In either case, the fused pad material creates a high spot on the disc. Every time that high spot comes around to the caliper while you're squeezing the brakes, the pads register that high spot as a little hump...giving you a pedal pulse.

When you did the ten 60-0 mph stops, you probably start to peel off the high spots. If you got the pads hot enough though, you may have started to lay pad material down on top of those high spots, which could exacerbate the problem. I didn't do a 60 to 0 because I'd read you shouldn't do a full stop as otherwise the pads might leave more residue on. So I did 60-10.

Don't think that's happened luckily, as the vibrations almost all went away after my bedding in process.


You need to scrape the discs cold. You don't want to heat them up and lay more material down on them until those high spots are removed. Hadn't thought of this. Will try it next.

You mean a few hard stops without heating up the brakes by back to back stops? Or to scrape them via one of the two solutions below?


There are a couple potential solutions.

Do you have a set of race/track pads? The compound in a track pad is more aggressive/abrasive. It will do a better job of scraping the discs vs. a road pad. If you install your race pads and drive them around a bit cold, they will act as a brake lathe and scrap off some of that pad material that fused to the disc. That is one option. Unfortunately, no.

Another option is to take a red Scotch-brite pad and scrub those high spots. Scrub them side-to-side. You may find that you can remove much of the pad material in this manner. How do you find out where the high spots are to just scrub those? Would it be where there's still rust? Or are those low spots?

A long time ago we did a video on swapping between street and track pads that is relevant to this topic. Once you understand what is going on with the pad material and how it interacts with the discs, then it becomes easier to find a solution. In this video I was 'scrubbing' the discs in my old C5Z06. You can watch the pad material peel right off the disc in real-time:

The rotor in the upper picture has improved over the last few days, but the bottom one still has that 1/2 inch strip of heavy rust... Just like in your video at the 2 minute mark. Which is odd, because it's where the brake pad touches yet it's not improved at all. I see that went away in your case, I wonder if it will just take more time.

Was just concerned that if it remains, it will cause uneven brake rotor wear and become a high spot...


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      02-24-2020, 12:02 PM   #10
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Quote:
Originally Posted by jritt@essex View Post

Another option is to take a red Scotch-brite pad and scrub those high spots. Scrub them side-to-side. You may find that you can remove much of the pad material in this manner.
PS. Instead of that pad, can I use sandpaper? What grit?
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      02-25-2020, 06:56 AM   #11
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You mean a few hard stops without heating up the brakes by back to back stops? Or to scrape them via one of the two solutions below?

I would focus on the solution below to clean the discs since you don't have any race pads on hand.

How do you find out where the high spots are to just scrub those? Would it be where there's still rust? Or are those low spots?

From everything you've written it sounds like the high spots are where the rusty pad imprints are, assuming you can still see them. If there are rusty spots, then yes, that is likely the pad material.

The rotor in the upper picture has improved over the last few days, but the bottom one still has that 1/2 inch strip of heavy rust... Just like in your video at the 2 minute mark. Which is odd, because it's where the brake pad touches yet it's not improved at all. I see that went away in your case, I wonder if it will just take more time.

It could just take a bit more time. In my case it took a second attempt the next day to get the whole disc clean. One other possible solution would be to flip the inner and outer pad on the side with the stubborn rust mark (or take a pad from the other side of the car and put it on the disc face with the mark). When you run a pad on a disc like you have, the two surfaces conform to each other. The disc wears a little, and the pad does as well. That's the point of bedding...mating those two surfaces together evenly and laying down a pad layer. A different pad will have a different shape to its face that will likely not match the face of that disc. That imperfect mating will potentially have a better chance at scrubbing the disc face vs. the ones that are already mated together.

Was just concerned that if it remains, it will cause uneven brake rotor wear and become a high spot...

Yes, you want to try and get it cleaned off now rather than later. Eventually it could become more permanent if not addressed.

PS. Instead of that pad, can I use sandpaper? What grit?

You don't want anything too abrasive..something like a 220 fine would be reasonable.
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      02-25-2020, 09:43 AM   #12
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Quote:
Originally Posted by jritt@essex View Post
You mean a few hard stops without heating up the brakes by back to back stops? Or to scrape them via one of the two solutions below?

I would focus on the solution below to clean the discs since you don't have any race pads on hand.

How do you find out where the high spots are to just scrub those? Would it be where there's still rust? Or are those low spots?

From everything you've written it sounds like the high spots are where the rusty pad imprints are, assuming you can still see them. If there are rusty spots, then yes, that is likely the pad material.

The rotor in the upper picture has improved over the last few days, but the bottom one still has that 1/2 inch strip of heavy rust... Just like in your video at the 2 minute mark. Which is odd, because it's where the brake pad touches yet it's not improved at all. I see that went away in your case, I wonder if it will just take more time.

It could just take a bit more time. In my case it took a second attempt the next day to get the whole disc clean. One other possible solution would be to flip the inner and outer pad on the side with the stubborn rust mark (or take a pad from the other side of the car and put it on the disc face with the mark). When you run a pad on a disc like you have, the two surfaces conform to each other. The disc wears a little, and the pad does as well. That's the point of bedding...mating those two surfaces together evenly and laying down a pad layer. A different pad will have a different shape to its face that will likely not match the face of that disc. That imperfect mating will potentially have a better chance at scrubbing the disc face vs. the ones that are already mated together.

Was just concerned that if it remains, it will cause uneven brake rotor wear and become a high spot...

Yes, you want to try and get it cleaned off now rather than later. Eventually it could become more permanent if not addressed.

PS. Instead of that pad, can I use sandpaper? What grit?

You don't want anything too abrasive..something like a 220 fine would be reasonable.
Much appreciated answering all my questions.
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