Braking Problem In The Wet

[Scotty C]

Morning All,

Ok so...I just returned from a recent 3000 mile across Europe, of which, most of it was sadly in the rain, and the braking problem that I experienced back in January 18 has risen its ugly head again.

The problem I get is that when I use the brake pedal, it is rock hard and does not depress, then due to the car not stopping as it should, I need to press much harder still and then something gives, the pedal sharply depresses, the brakes engage and the pads violently grab the discs, jolting me forward. At times, when the brakes do start to eventually work, it even feels like the front end swings left or right momentarily too, like being hit by a side wind. I carry on for a further 5-10 minutes and then the pedal becomes hard again.

Basically, the combined conditions that causes this issue are that it needs to be raining, the wipers need to be on, I need to be doing motorway/dual carriageway driving and anything over around 50-60mph for a period of 15-20 minutes onwards. In the dry, and wet without wipers on, the car performs perfectly normal.

I eventually had to trick the car into believing it wasn't raining and use the manual wiper function, pressing down every 3 seconds or so, just so the brakes would be ok. This problem persists until the wipers are off. I decided to run the ACC in the rain with wipers on just to see how this affected the braking and surprisingly, the car braked like normal and without any problems or jolting forward.

I am confident it has something to do with the brake disc wipe function somehow as this is the only connection I think there is between the wipers being on and the braking system. I don't think the problem was dealt with properly back in January and, as the car is not my daily drive, I have not driven with the combined conditions to notice that the problem still existed.

The dealer's Master Tech seems stumped, as do the tech guys at Audi he is sending questions to for answers... I've told them it's unacceptable and I do not want the car back until they are sure they know the reason behind it and the car is fixed. It is extremely dangerous to drive in the wet and I do not want to put myself, or my family, through that ordeal again.

Any thoughts would be much appreciated and thanks in advance...

[Daveperc]

That certainly doesn't sound right!

I have the opposite problem when running in the wet - the wipe function doesn't really dry the brakes so when braking after a prolonged run in the wet they are initially (1-2 secs) not very effective at all - the result, much like you, is that you brake harder and then they suddenly catch much harder than you want. I have ceramics BTW and am told that the frequency etc of the wipe is different but in all other respects the system is the same.

My solution so far has simply been to ensure I brake early and fairly frequently to avoid the problem. I may also have to train myself to go back to cadence braking like in the old days.

Can the brake functioning (and wiping) be monitored in real time with VCDS?

[Covkiller]

You need to drop anchor

[RS6chris!]

That certainly doesn't sound right!

I have the opposite problem when running in the wet - the wipe function doesn't really dry the brakes so when braking after a prolonged run in the wet they are initially (1-2 secs) not very effective at all - the result, much like you, is that you brake harder and then they suddenly catch much harder than you want. I have ceramics BTW and am told that the frequency etc of the wipe is different but in all other respects the system is the same.

My solution so far has simply been to ensure I brake early and fairly frequently to avoid the problem. I may also have to train myself to go back to cadence braking like in the old days.

Can the brake functioning (and wiping) be monitored in real time with VCDS?

I was in really heavy rain at high speeds....hit the pedal and for a few secs(or so it seemed) absolutely <beep> all!!

I <beep> me self then they bit!!

I have ceramics also

[Scotty C]

You need to drop anchor

What I needed was a change of underclothes !!!

[PieterZ]

Damn that is not good at all.

[sasha320]

I have had this 'collapsing brake pedal in the wet' problem as well.

would be great to heat what Audi say - have they witnessed the fault?

[Foxy]

I've experienced the same, my car doesn't have ACC or ceramics but I've had two hairy moments in the wet now on motorway runs, the first time I thought the car had aquaplaned but the second time was in daylight and there was no standing water.

[Scotty C]

I have had this 'collapsing brake pedal in the wet' problem as well.

would be great to heat what Audi say - have they witnessed the fault?

Not yet... Unlikely they ever will. They are waiting for a brake servo testing tool which apparently is on order but not available for another FOUR weeks !!! We will be having words monday morning... but will keep you updated.

[Scotty C]

I've experienced the same, my car doesn't have ACC or ceramics but I've had two hairy moments in the wet now on motorway runs, the first time I thought the car had aquaplaned but the second time was in daylight and there was no standing water.

I don't have ceramics either... just standard steel discs... This is a serious fault that someone, somewhere must be able to identify...

[bn8959]

I posted another thread about odd braking behaviour I’ve experienced. Almost the opposite to the OP, significantly more braking than less. Wonder if there is a link.

[Daveperc]

OK - epic drive from SW Wales at the height of Storm Deirdre yesterday - 60MPH cross winds and rain that would have made Noah get a shift on!!

I think my problem (not saying this is everyone's) is simply that the huge ceramic discs and pads pick up so much water that the wipe function simply doesn't clear them. If I drove for more than a couple of minutes without braking then they were useless for about a second or so until the water had cleared off. The art was to brake moderately hard and be ready to lift as the bite came in, though that wasn't always easy to predict. It was made slightly more difficult by the fact that on more minor roads the nearside can be picking up a lot more water from the side of the road so that as they bite, the drivers side bites first.

I'd still like to be sure that the "wipe" function is set up correctly, but not sure if there is anything that can be monitored.

Having said that, it is still definitely the car for the conditions - so stable and planted even at speed through standing water. The Mich PS4S were stable through puddles, rivers and worse, even when the wind was doing its best to take the car straight across the road.

And for those wondering if winter tyres would be better, I monitored the tyre temp quite a bit and it ranged from about 17-23C most of the way, even in the wet, so they are well within their safe normal range at speed.

Stay safe guys!

[brab]

I do not have ceramics and have experienced this multiple times (only in wet), it has been mentioned on this forum before.

Our cars are equipped with a brake booster that sometimes reacts when it shouldn't, Chris Harris had this same issue (he even had a car towed to the dealer coz of it) and discussed it with Quattro head:
https://www.goodwood.com/grrc/road/the- ... state-car/
https://www.goodwood.com/grrc/road/the- ... is-harris/

"In reality all that happened was I had less brake fade than I’d expected, but it felt like a third-party had hit the brakes for me because the reaction to my input was so foreign.

The next time I drove the car, I wasn’t travelling so quickly, and the middle pedal remained quite normal. As it would happen, I was at the Paris motorshow the following week and bumped into Stephan Reil of Quattro Gmbh. I told him about the braking anomaly and he nodded his head: “To stop the feeling of having a long pedal when you are really working the brakes we fitted a booster which brings the pedal back up when it’s getting long – sometimes it can come back right to the top of the pedal travel.”"

[superlightr]

“To stop the feeling of having a long pedal when you are really working the brakes we fitted a booster which brings the pedal back up when it’s getting long – sometimes it can come back right to the top of the pedal travel.”

but that's not true - this happened to me on a normal slow commute in - I gently touched the brakes and full on braking came on for a second. Was not honing or driving fast in anyway whatsoever on the whole journey. There was no long pedal/fade or anything it was emergency braking from a light touch. Had only happened a few times but it did happen. I don't accept Reil explanation as its not what happened to me or what it sounds like to others here.

standard brakes. with regards to ceramics - I don't belive they can pick up so much water steel or cermics that you get that emergency brake - never had it on any other car either with ceramics or steels - DB9 M5 E63 AMG, 911tt's just the RS6

[zappy-chops]

Geez, this sounds like a worrying issue. Don't know if I am reading too much into the scenarios described but it sounds dangerous and should be the subject of a recall. I have only just bought my RS6 and I love it, but if this happens once to me, and I feel that safety is compromised, then the car is straight into Audi and if they can't fix it, claim they know nothing of the issue, or give the classic dealer response of "it worked fine when we tested the car so if we can't see it we can't fix it", then it's goodbye RS6.