Potential wet braking issue

[bberg22]

Not sure if others experience this or not but it is becoming concerning. When it is raining out it feels like i have seriously degraded braking performance for the first part of the brake pedal travel. The pedal feels like it travels further than when dry and does not bite. I ultimately end up giving it more pedal force which then ends up in ABS kicking on and the feeling of somewhat uneven brake application (slight pull to one side sometimes). This is mostly only on the highway when this is noticeable, and I am on stock brake rotors/pads, fluid is only 9months old. I have never felt this sort of behavior on other cars, it feels like the brakes are not clearing the water off the rotors or something. I read that these cars have some sort of system to clear water off the rotors by applying the brakes?

Any thoughts on this? I will ask the dealer at next service but want to get this resolved before end of Warranty (currently at 46k miles). Thanks

[will13k7]

not normal for all oem parts/pads. my s4 never did that. good to get it checked out. might also be related to tires not getting enough traction, but the increased pedal travel makes me think not, unless that part is all in your head. What tires are you running? summers, all-seasons? all-seasons suck in the rain.

[bberg22]

New set of winters, they are past their break in with over 1000 miles on them. The grip in the rain is great with the tires. It almost feels like when breaks get hot and you get reduced stopping power and then if you push hard you get ABS to kick in. Harder than normal to modulate in the wet.

[LYKUNO]

... I read that these cars have some sort of system to clear water off the rotors by applying the brakes?

Any thoughts on this? I will ask the dealer at next service but want to get this resolved before end of Warranty (currently at 46k miles). Thanks

Found the following on the net: A specifically 'tuned'[6] "sport-biased" Bosch[13] ESP 8.0[6] Electronic Stability Programme[5] is standard, and includes Anti-lock Braking System (ABS)[5][6] and Electronic Brakeforce Distribution (EBD),[5][6] and Brake Assist (BA). This ESP system has three user-selectable settings: the standard default full protection mode, increased slip mode (which turns off the ASR and EDL), and ESP fully off. A useful feature[6] of the ESP 8.0 is 'disc wiping', whereby in wet weather the ESP system applies the brakes frequently but momentarily. This removes water from the disc and pad surfaces, and helps to maintain the braking performance of dry weather. This operation is undetectable by the driver.

Pretty sure that the B8 (and likely the B8.5) series have ESP 8.1 (or later), and think I've read in the owners manual that the disc wiping feature is included on the S4. Not sure how it works or what sensor would detect presence of wet conditions and then operate the brakes momentarily to "wipe" the discs.

Here's an animation of how the feature works on a Q7 ...


https://www.youtube.com/watch?v=5n99lNA0ItA

A bit more on the feature for VW models ...


https://www.youtube.com/watch?v=guxKEOIFuts

Okay, one last comment. Just found a bit more info on the feature. It's enabled when the wipers are turned on, assuming the feature is activated with VCDS. Here's a screen shot from this VW turbodiesel forum thread (http://www.myturbodiesel.com/threads/disc-brake-wiper.18930/) that should be helpful:

http://www.myturbodiesel.com/data/photos/l/1/1332-1441194562-b37414d6f6aba88bcf752f2bdb701633.jpg

Perhaps the feature is not enabled on your car? Or maybe you use Rain-X or some other product to avoid using your wipers?

[bberg22]

That is interesting, I do use Rain-x and sometimes don't run my wipers. I will have to pay attention to that. Great info! Ill report back after I can test that!

[MrFunk]

I have aftermarket drilled and slotted rotors.
They get water locked pretty bad in the winter (slushy roads) and summer rain - especially when roads are soaked.
I don't remember how bad it was when I had all OEM components but it was not as bad.
I also minimize how much I use my wipers.

[chilort]

I have Hawk 5.0 pads and they've made me pucker a few times when cold and more so when cold and wet. Once warmed up they are fine. I run a solid rotor on a 2-piece rotor setup. I'll probably be going back to Hawk HPS after the 5.0s are done.

[bberg22]

I noticed improvement today with snow/wet conditions leaving my wipers in auto mode. Glad to have learned that this exists but too bad I have to have my wipers on for it to work.

MrFunk - I thought the slotting should help in the wet? I was considering slotted for my next rotors and this was port of the reason why.

[DannyDeez]

Not sure if others experience this or not but it is becoming concerning. When it is raining out it feels like i have seriously degraded braking performance for the first part of the brake pedal travel. The pedal feels like it travels further than when dry and does not bite. I ultimately end up giving it more pedal force which then ends up in ABS kicking on and the feeling of somewhat uneven brake application (slight pull to one side sometimes). This is mostly only on the highway when this is noticeable, and I am on stock brake rotors/pads, fluid is only 9months old. I have never felt this sort of behavior on other cars, it feels like the brakes are not clearing the water off the rotors or something. I read that these cars have some sort of system to clear water off the rotors by applying the brakes?

Any thoughts on this? I will ask the dealer at next service but want to get this resolved before end of Warranty (currently at 46k miles). Thanks

Literally every car I've ever driven in the rain on the highway does this. The S4 is the only car I've had that does not do it and thats because it applies the brakes on its own as mentioned below.


Found the following on the net: A specifically 'tuned'[6] "sport-biased" Bosch[13] ESP 8.0[6] Electronic Stability Programme[5] is standard, and includes Anti-lock Braking System (ABS)[5][6] and Electronic Brakeforce Distribution (EBD),[5][6] and Brake Assist (BA). This ESP system has three user-selectable settings: the standard default full protection mode, increased slip mode (which turns off the ASR and EDL), and ESP fully off. A useful feature[6] of the ESP 8.0 is 'disc wiping', whereby in wet weather the ESP system applies the brakes frequently but momentarily. This removes water from the disc and pad surfaces, and helps to maintain the braking performance of dry weather. This operation is undetectable by the driver.

Pretty sure that the B8 (and likely the B8.5) series have ESP 8.1 (or later), and think I've read in the owners manual that the disc wiping feature is included on the S4. Not sure how it works or what sensor would detect presence of wet conditions and then operate the brakes momentarily to "wipe" the discs.

Here's an animation of how the feature works on a Q7 ...

[video=youtube;5n99lNA0ItA]https://www.youtube.com/watch?v=5n99lNA0ItA[video]

A bit more on the feature for VW models ...

[video=youtube;guxKEOIFuts]https://www.youtube.com/watch?v=guxKEOIFuts[video]

Okay, one last comment. Just found a bit more info on the feature. It's enabled when the wipers are turned on, assuming the feature is activated with VCDS. Here's a screen shot from this VW turbodiesel forum thread (http://www.myturbodiesel.com/threads/disc-brake-wiper.18930/) that should be helpful:

[IMG]http://www.myturbodiesel.com/data/photos/l/1/1332-1441194562-b37414d6f6aba88bcf752f2bdb701633.jpg[IMG]

Perhaps the feature is not enabled on your car? Or maybe you use Rain-X or some other product to avoid using your wipers?

Great post. You are correct, it is mentioned in the owners manual.

[bberg22]

My Previous car never had the issue with wet brake feel. I did not think to check the manual. Thanks for the info

[MrFunk]

I noticed improvement today with snow/wet conditions leaving my wipers in auto mode. Glad to have learned that this exists but too bad I have to have my wipers on for it to work.

MrFunk - I thought the slotting should help in the wet? I was considering slotted for my next rotors and this was port of the reason why.

My rotors are drilled and slotted. Just more crevices for water to pool/flow though.

[OnEaNgRyBuNnY]

My ecs two piece drilled and slotted rotors and hawk hps setup does this. I do not remember it doing this stock at all. As the brake setup aged, this decreased greatly. Can't say I've noticed any change with wiper use.

Think it may have to do with the parking brake setting being calibrated improperly/not recalibrated? I would assume that issue would be noticeable dry or wet tho but?????

I've never experienced this in any condition in multiple vehicles before my B8.5.

Sent from my iPhone using Tapatalk

[MrFunk]

My ecs two piece drilled and slotted rotors and hawk hps setup does this. I do not remember it doing this stock at all. As the brake setup aged, this decreased greatly. Can't say I've noticed any change with wiper use.

Think it may have to do with the parking brake setting being calibrated improperly/not recalibrated? I would assume that issue would be noticeable dry or wet tho but?????

I've never experienced this in any condition in multiple vehicles before my B8.5.

Sent from my iPhone using Tapatalk


Every single vehicle I've owned is susceptible to water "soaked" brakes. Drilled and slotted are much more susceptible though.
The worst is when it's very cold out and snow gets packed in the slots/holes - even worst is when water freezes on the rotors (perhaps after parking the car after a drive) - very dangerous.