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BMW 3-Series and 4-Series Forum (F30 / F32) | F30POST > Technical Forums > Suspension | Chassis | Brakes > "Grabby" pad noise in wet weather
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      03-04-2016, 04:22 PM   #1
RPM90
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"Grabby" pad noise in wet weather

My 340i has recently developed an odd behavior and noise.
I have not confirmed this twice in wet weather.

When it's wet outside and I come to a complete stop, when I let go of the brake pedal there is an ever so slight delay, but more than that there is an odd type of noise from the left front caliper.
It sounds like a "grrrr" for the same delay period and then all goes quiet and normal.
It sounds and feels like the caliper is sticking for less than a second.
And, it's only on the left front, right front no noise and none in the rear either.
This just started this winter as the temps got warmer over the past few weeks and the road conditions are wet.

I know that modern BMW's have a "hill assist" function where the brakes will hold for a split second when the brake pedal is released, and it's very helpful in manual cars as it was in my 135i with MT.
It's quite pointless in cars with AT, but I think all modern BMW's have this feature regardless of trans type.
So, I think that may be the source of why there is a delay on pedal release, as it allows the pad to light rub the rotor on take off.
But I wonder why the pad makes that odd "grrp" sound as the car starts to move and only when it's wet?

Anyone else notice this in their 340i or 335i Msport?
The 340i Msport brakes are overall nicer than my 335i Msport brakes.
With my 335i Msport the pads felt a bit too "grippy" with too much initial bite. The 340i Msport pads are smoother.

When the roads are dry I get no noise at all.
When wet there is noise, and what feels like a sticky caliper.
Very odd.
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      03-05-2016, 10:05 AM   #2
Zel335
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Does this happen the entire time when it's wet out or only for a little bit until the pads heat up?

If you think it's an issue with you having that 340i I would just have the dealer replace the pads, this could be the quickest resolution to the issue.
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      03-07-2016, 01:41 AM   #3
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Solution is to take the caliper off once a year and clean/lubricate the slide points.If still the problem persists, you must visit top rated BMW mechanics.
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      03-20-2016, 12:49 AM   #4
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Might want to do a half dozen or so of intervals stopping from high speed all the way down to low speed pretty quickly (but not completely stopping). This will heat up the rotors and clean off any harmful residue that might be stuck on there. Worth a shot. Just gotta find a place where you won't get a ticket for going 70-10-70-10-70-10
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      04-14-2016, 04:06 AM   #5
RPM90
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Quote:
Originally Posted by arminvb View Post
Might want to do a half dozen or so of intervals stopping from high speed all the way down to low speed pretty quickly (but not completely stopping). This will heat up the rotors and clean off any harmful residue that might be stuck on there. Worth a shot. Just gotta find a place where you won't get a ticket for going 70-10-70-10-70-10
Yes.
I bed new brakes all the time and ever time I get a new car or replace the brake parts. Bedding was done within the first 100 miles when I picked up the 340i last September.

Even though it feels like pad material "build up", this only feels this way when it's raining and the rotors and pads are wet.
When it's dry all feels normal.
It really does feel like the calipers are slightly "sticking", or very slow to release, when it's wet.

The brakes on my 340i Msport have a nicer pedal feel and smoother bite than the brakes on my 335i Msport. The 335i Msport came with a higher friction pad that BMW included on the stock brakes for the Msport.

At this point either there is something strange with the pad material when it's wet, or, the hill assist is over active when it's wet outside.
I've also read that when it's wet outside the calipers will engage every so lightly in order to keep the rotor and pad dry for when the brakes are engaged. However, that part shouldn't affect the brakes when starting from a full stop.
I'll have to have the BMW tech take a look, but if it's not wet when they test the brakes, then it'll come back with "no problem found", and that would be a waste of time.
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      04-14-2016, 04:10 AM   #6
RPM90
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Quote:
Originally Posted by msginnie View Post
Solution is to take the caliper off once a year and clean/lubricate the slide points.If still the problem persists, you must visit top rated BMW mechanics.
That's a solution for older brakes with lots of miles on them.
New BMW's don't and shouldn't need that.

BMW is one of the only car makers that actually replace the brake fluid every 2yrs/24K miles. That's always impressed me because that's what I do with all my cars when I worked on my own cars.
Having leased/owned BMW's since 2003 I don't have to do anything because BMW takes car of all the needed maintenance.
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      04-14-2016, 04:13 AM   #7
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Quote:
Originally Posted by Zel335 View Post
Does this happen the entire time when it's wet out or only for a little bit until the pads heat up?

If you think it's an issue with you having that 340i I would just have the dealer replace the pads, this could be the quickest resolution to the issue.
Yes. When it's wet out and the brake parts are wet, this happens at every full stop, even if the brakes are hot.
As I noted in a recent post it feels like the calipers are releasing too slowly.
That's why I'm suspecting something with the hill assist.
If not that, then it could be the pad material BMW is using on stock Msports with the stock Msport brakes.
But if that were true, the others would feel it as well.
Maybe I should post this to the general forum to get more responses.
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