FMOB

Look at the rating plate with the tyre pressures on (by catch on the drivers side door pillar), this will tell you the wheel/tyre combos that will fit as standard and doesn't knock the speedo out, etc. If none of these work then go off-piste with calculators and the malarkey. As for wheels, part numbers, etc - you need to find the parts diagrams online for your car as these will list part numbers for the OEM wheels, obs check with Audi the part number is correct before buying so you get the right wheels.

Regarding the auto close of the tailgate on the Avant, be careful what you wish for applies. It seems (and this is a guess) that my Avant had this enabled, the end result was having the tailgate close on me on several occasions, multiple times each occasion without any logic to it whilst loading up. Being the filling in a tailgate sandwich isn't particularly nice and it does hurt. The final straw was the damn thing closing unexpectedly in the dark as I was walking towards it, result was a concussion headache for a week. There are dim downwards facing lights (when the tailgate is open) but nothing that faces away that someone who is walking towards the rear of the car can see. My old b7 Avant had the rear facing lamp but the C8 does not! So many valuable features have been binned. At the end of day, users need to know whether doors and tailgates are open or closed and be confident they in the same position they expect them to be in. Regarding pressure washing the sunroof, I would expect it to be fine but go lightly on the seals and gaps. They are designed to stay sealed when driving at high speed but everything has a design limit, my other car has a sunroof and gets jetwashed regularly with the nozzle about 3 foot away and no issues.

I found a couple threads on the issue hence the question. https://www.ttforum.co.uk/threads/bag-in-coolant-tank-reservoir-bursting.2030154/ https://www.pistonheads.com/gassing/topic.asp?h=0&f=23&t=2056688 Would not put it past Audi to keep doing something daft like this and leave owners to carry the can. If my car has this I will get it removed if it has potential to cause issues, I do not need any more hassle from the S6 POS edition.

Read about this affecting VW's, etc so is this a potential problem for the C8 A6/S6 vehicles or has someone had a bit of common sense and designed this problem out?

That message is a complete pain in the preverbial, I had the same issue and ended up doing the same thing of logging out of the account, app, etc. Modern Audis are not user friendly, they (Audi) think they are being clever but they just annoy anyone with half a brain.

I was wondering this, good to have some else shed a bit more light on the issue. Could you provide a photo of your seats as I find identifying them a bit confusing. Happy to change the drivers seat if it solves this problem.

I have the supersport seats, you cannot lower the front independently, the rear can be raised relative to the front but this also raises the overall seat height. Can't believe Audi can get this so wrong.

Exactly the position I am in, I have a wedge cushion to try and reduce the pressure the seat creates on the back of the thighs near the knee. Really just need to set the seat base flatter but the adjustments don't allow that. I suspect it is down to pedal offset which is not something that can be fixed. Car is a pile of dog doo-doo.

My 2021 S6 Avant collects water in the tailgate and then has a waterfall each side the boot is opened. I am not sure if the roof spoiler fills or if it is the small blades either side. Basically it is more !Removed! design on a car that is a big pile of !Removed!, all the journos who reviewed the car and said it is wonderful should hand their cards in.

Definitely terminal, I think the gangle pin in the giggle box hiding under the air filter is shot. Only fix is to scrap it, sorry to be the bearer of bad news. Am I doing this right?

Do check for any DTC's to see if there any dodgy sensors, if none are shown it could be the siren battery backup failing, the siren isn't intelligent and diagnosis is usually by swapping with a known good one or just replacing batteries in the old one. If the siren is as I remember, you need to cut it open to get to the batteries so not an easy DIY job. Just my 10c's worth.

45,000 miles so far this year, I am curious why the huge mileage, taxi driver or just long distance commuting? Firstly, what sort of driving are you doing? Is it all motorways or stop/start traffic as that will impact the amount servicing needed. If you are on motorways all day then use the flexible servicing where the car may well stretch the service intervals as modern oils are much better than they used to. If I commuted the 70 miles each way to the office, 5 days a week that is 33,000 miles p.a. and 3-4 services over a year on the fixed servicing schedule. And please tell us you are using an indie rather than a stealer for the servicing, the latter will think it is Xmas every 7 weeks.

The length is very noticeable so the higher trim variants i.e. black edition and vorsprung.. have rear wheel steer and probably makes the vehicle length less noticeable. Width wise, it is wide no doubt about that. Most small roundabouts aren't an issue if you are careful, never taken it in a multi-story so cannot advise on that though I expect you would need to be careful. Other thing is the slab sided design does make knowing where the lowest parts of the bumpers are relative to objects difficult hence the cameras are useful, I managed to knock down a low wall almost as soon as I got it home, 8 years at the house and never tapped anything with 2 different cars until the C8 came along...

Have you tried Dialynx nr Swindon?

Best of luck with getting the rattles fixed, this is a known issue but expect to be fobbed off. Mine has been into the dealer twice for dash rattles, the fixes lasted a week tops and I have a little pile of broken tabs collected from the footwells. If you Google Audi A6 C8 dash rattles there is a guide for a bit of diy fixing of the dash and get a decent set of trim tools if you decide to have a go.