When it's really wet...

[Daveperc]

OK - just interested to see if others have similar experience...

Some of you have probably noticed we had a bit of rain last weekend - I drove through several TORRENTIAL showers on the motorway. Two issues surprised me:

1) After a few minutes of very wet driving I went to brake, to find that the pads/(ceramic) disks were sufficiently soaked that for a second or so I had little braking - with increased pressure they cleared and returned to normal function. After this happened for the second time I took to "drying" the brakes for a few seconds periodically so I had something when I needed it. Don't think I ever had this on the C5.

2) At "motorway speeds" I noticed the car seemed to be "dancing" as though each wheel in turn was momentarily aquaplaning before recontacting the tarmac - it created a kind of vibration at about 1/2Hz (ie each wheel was out of contact for 1/2 sec each time. Felt really weird, though equally I still had full control (AFAIK!!). Tyres are quite worn Dunlops, so hopefully a new set of Michelin boots will cure it in the next couple of months.

I have driven the same sections of road in the C5 in similar conditions and speeds and never experienced these issues!

So, how has your really wet weather experience been??

[doodlebug]

That’s entirely normal for ceramics, they need to be warm and dry.

As for the other phenomena it’s not one I ever came across.

[skirs6]

As said ceramics in wet conditions are not great you need to dab the brakes to try to dry them just in case you really need them. As for the other issue maybe down to the wider tyres and the weight as the C7 is much lighter than the C5.

[MikeFish]

... the C7 is much lighter than the C5.

You been in the pub again? C7 is heavier than a C5.

[MikeFish]

Agree with the above. There was a thread on here about 2 years ago about the ceramics performance in the wet.
Not sure what the other issue is but I had mine aqauplane a few times when my original Dunlops were worn though.

[rtd]

My Yokos were rubbish in the wet and Dunlop’s useless on my C6, the Michelin’s are a revelation so there is hope!

I had ceramics which were a retro fit on my C6 and in wet conditions I had the same problem initially when braking. I was told that if they had been fitted at factory then they are coded in such a way that in wet conditions the pad pulsates off the disc - so that it’s ready and dry when needed. I’m not sure if that was true or not as I was never able to acquire the coding.

[MikeFish]

My Yokos were rubbish in the wet and Dunlop’s useless on my C6, the Michelin’s are a revelation so there is hope!

I had ceramics which were a retro fit on my C6 and in wet conditions I had the same problem initially when braking. I was told that if they had been fitted at factory then they are coded in such a way that in wet conditions the pad pulsates off the disc - so that it’s ready and dry when needed. I’m not sure if that was true or not as I was never able to acquire the coding.

I thought all modern RSs did this. And the coding changed the rate of wipe?
I've never heard of this as being an issue in the B7 so maybe the C7 has the wipe rate set wrongly. Not sure if the frequency of wiping can be changed with VCDS? Maybe change it to steel discs (not sure if steels are wiped more often or less often).

[Daveperc]

Many thanks guys - glad to know I wasn't dreaming!

Not had ceramics before so had not appreciated the need to "wipe" them - will know in future

Any RS techs on here can answer the question about them "self-wiping", and the settings? Or do I need to ping my mate direct??

And good to know others have struggled with worn Dunlops - definitely will switch to Mich soon!!

Dave

[rtd]

Dave seeing as your car had the ceramics as OEM fit maybe go to dealer and ask them to look into it?


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[dasquade]

The ceramics do has a clean whipe feature, i would need to check my settings (s6 ceramics tough) but it surely has different settings then steel disks.
Ceramics are indeed 'useless' for a moment like when you washed the car (remember that one aswell so you don't get suprised ) and they indeed need to be warmed up.
*normally the car should have to correct settings if factory ones, but never know, but depending on how extreme wet and cold it was, you need to be aware of them.

As for the aqua....i'm guessing 90% comes down to tire tread thickness as you clearly mention they are pretty worn...add the fact it are pretty wide tires.
Carefull, even it has quattro and sportdiff .

[Daveperc]

Thanks for all the observations.

Just had a FB chat with my favourite Master Tech, and he has pretty well confirmed everything here. "The car will have brake wipe function which periodically brings pads in via abs pump to generate heat to help dry ceramic brake out . "

Also occurs to me that the "dancing" I sensed is probably this wipe function at work as the brake is applied to each pad in turn.

Looks like there is a learning curve for me to adapt my braking style in very wet conditions - you live and learn!

[RS6chris!]

Ramics can be scary when wet....sometimes when I’ve washed car and jet washed, first time away it’s like “shot” when u dab brakes!

[skirs6]

... the C7 is much lighter than the C5.

You been in the pub again? C7 is heavier than a C5.

Maybe it was me that was heavier then

[drhex]

Ceramics are wiped about twice as much as steel in the rain. This is coded in the brake control unit, took me a while to figure out how when I retrofitted my C7.
Florian

[Surrey Sam]

As mentioned, its different coding for the ABS module with Ceramics to increase the pad wipe frequency. This is to try and minimise the poorer performance when the discs are wet/soaked. The pad wipe function will only work when the wipers are in the auto or on positions; as it uses the rain sensor in the windscreen/mirror to know when it’s raining, so the pad wipe function can then be activated.