Yes, I've found the S8 astonishingly efficient at putting the power down with almost unbelievable acceleration for the conditions......

However, stopping.... these cars have to obey the same laws of physics as any other car (F = Mu x N, and all that)
Other than the clever electronics, another huge factor is the contact/ weight ratio
ie when its slippery, the larger the tyre contact area (footprint) with the road surdace will start to work against you inasmuch as it will take less force to break traction for the given area of contact. Narrower tyres could well be a distinct advantage under certain conditions, as they 'cut through' the surface rather than 'gliding' on it (on snow & ice). Bigger may well look good, but its not always better.

i use 17" in the winter i had primacy's on a 55 profile never had any traction problems, i dont really commend the extra cost of changing to a winter tyre when i use the 17's every year in the snow they are fantastic and they cover up most of the breaks so less crap get's in at the wheels and disc's just drive with more caution, i agree that the traction is great but the breaking is hairy to say the least the abs dose tend to have a slight aneurysm when on a icy surface almost a shame it cant be turned off when needed, just my 2 pence worth +++

Well I've now solved the problem for my S8!

Today I acquired (at maybe a bit over the odds) an "average" (few light scratches) full set of 5 17" * 7.5J Avus wheels that I'm told originated on a 2002 S4.

Just got to decide on tyres and how many (probably only 4) and get them ordered and fitted. Oh, and tidy up the wheels a bit first.

I'm going to TRY and see if I can get them on without SWMBO even noticing.
I suspect that the subtlety of 18" vs 17" of the same design with deeper tyres will pass her by.... :ROFL:

lol nice one +++
Thats what I call a creative solution :D

Thanks. :cheers: Just ordered some Goodyears to fit on them, now I need to get cracking on cleaning them up.

why not show us some pictures then, we all love to see creativity at work and of course before and after's, top job wish my wife was not a petrol head she notices any subtle change and then i get a grilling of where its come from and the dreaded "how much did that cost" question Haha +++

I'd be embarrased. :o
The befores are so-so and I'm not going to get them done professionally as it's just for winter tyres. Just a rub-down and rattle-can job and I'm not very good at that.

Or did you mean comparing the car with 18's and 17's? I can probably do that.
Should be fairly similar though the centre caps are different - not sure if I can swap them.

Can't quite decide on what colour to use though. Ford Moondust Silver is reckoned to be a pretty good match to most alloys and Halfords Silver (for wheels) I've read is quite grey - which actually might be a good thing as my car is Agate Grey.

Well I can't, they're the same diameter but very different depth to the central mounting.

And I've decided to try the Moondust Silver, so lets see how it works out!
(I did a test on the centre caps and it looks a very good match) +++

Mobile tyre man called in briefly this afternoon and stripped the tyres off, so I'll start rubbing down tomorrow, weather permitting. He only charges £10+VAT a wheel all in (including disposal) which isn't bad for "darn sarf".

Is it just for removal? Local garages here charge £30-45 for removal, new valve, fitting and balancing for a set of 4 tyres and disposal is additional £0.50 per tyre.

£10 per wheel (+VAT) for removal, new valve, fitting, balancing, fit to car and disposal of old tyre.

The local tyre shop told me their "standard charge" was £21 each for tyres they don't supply with disposal another £1.20 (£1 + VAT).
(Home Counties prices!)