Brake Pedal Fault

[Scotty C]

Evening All...

Ok so now on two occasions, both motorway journeys at about 80mph on European roads, I've used the brake pedal to naturally slow down and it has felt like nothing is happening. In both cases, usual pressure was applied but it felt like the pedal resisted my input and hardly depressed at all, then releasing itself, jolting me forward like I'd stamped on the pedal. Quite scary when the car decides to do this, usually resulting in a change of underclothes. At least one journey was heavy rain, although can't see this as being a contributing factor.

I read somewhere of others having a similar problem but unsure of the cause or outcome. Car is booked in for an urgent inspection but not very confident they will know what the intermittent fault is as almost impossible to recreate.

If anyone has any understanding of this I'd be interested to know ?

Thanks

[Markp]

I have an odd issue where the car seems to brake for me - at least initially - when I switch to the brake pedal quickly. For example, I come around a corner and see something ahead I don't like the look of, so come off the gas and touch the brake in case, and the car applies much heavier braking than I need and everyone's heads momentarily snap forward. Am I going mad or does the car have an auto assist function? And could this be related to your issue?

[Foxy]

Reading this has prompted me to post as I previously thought my experience was due to the road conditions (standing water on the M5), but now I'm not so sure. I had to brake in very wet conditions as a car had just hit the barrier and spun across the carriageway, initially the pedal was soft to the point of nothing and then bit hard, too hard, nearly sending me into a spin. It was a nasty moment but I put it down to the wet road but now having doubts as it was something I can't ever remember encountering in 30 years of driving.

[MikeFish]

I recall someone on here ages saying they got chatting to an engineer that worked for audi (and possibly on the C7) and they said that our cars had a feature that can vary the amount of brake pressure required to apply the brakes so if the car detected excessive brake pedal travel was required it could apply more braking effort for you effectively stiffening the pedal. Never seen this documented anywhere. And of course the cars have brake assist so can apply the brakes harder in an emergency and if you have the Assistance Package you also get Active Brake Guard that will brake the car if it thinks you are going to have a collision and Adaptive Cruise which regulates the speed with the brakes, so quite a few different systems that give the car the ability to brake independently of what you are doing. Any of these could be having a bad day and apply brakes for you but the issue you describe sounds like the first one that I mentioned above and sounds like the car adjusting the brake pedal effort required.
I think there was a thread about this before after Rob had similar instances (always in the wet) with his ceramics.

[zzz]

I have an odd issue where the car seems to brake for me - at least initially - when I switch to the brake pedal quickly. For example, I come around a corner and see something ahead I don't like the look of, so come off the gas and touch the brake in case, and the car applies much heavier braking than I need and everyone's heads momentarily snap forward. Am I going mad or does the car have an auto assist function? And could this be related to your issue?

I first came across this issue in a crappy Renault hire car circa 2007, I'm normally quite quick footed with changes from accelerator to brake etc. This car was making me emergency break when i quick footed to the brake pedal, I had to dial back my movements to stop the issue. That system was in its infancy at the time and has improved. I've not had it in the RS6 so they must have moved the technology on significantly. Just googled, it's BA or BAS: https://en.wikipedia.org/wiki/Emergency_brake_assist
"By interpreting the speed and force with which the brake pedal is pushed, the system detects if the driver is trying to execute an emergency stop, and if the brake pedal is not fully applied, the system overrides and fully applies the brakes until the anti-lock braking system (ABS) takes over to stop the wheels locking up.[1]"
It's a PITA but I suppose it saves the less aware from crashing into the back of us.

[bn8959]

I’ve had this issue too. Twice it has occurred in 9 months of ownership. For me both times it was just a very gentle application of the brake pedal caused significantly more braking than I expected causing a fair old jolt (followed by accusations from my wife of giving her whiplash). Both times the brake pedal went light (as if it were being depressed for me).
I’ve booked mine in too for Audi to have a look, but I doubt they will find anything.

[Scotty C]

Car is booked in Friday 2nd - be interesting to see what they come back with. They have already said it will most probably need a test drive to find the fault. I wished them good luck as I've just done a 1200 mile stretch and it never happened. Will update when I know any more.