Well then this gets a bit more complicated as it becomes more about owners feeling/looks requirement and availability of different sizes.

So far what I found out is that 2006 A4 org tire size was 235/45 R17.

Alternative was 235/40 R18.

If org is 235/45 R17 and speedo is calibrated for it, then...

By X driveshaft speed:
Tire size - tire revolutions per mile - speedo mph.

235/45 R17 - 796.32 rpmi - 65.00 mph.
235/40 R18 - 793.97 rpmi - 65.19 mph.
245/40 R18 - 784.25 rpmi - 66.00 mph.

Owner probably prefers to stick with rim size he haves and so he haves two feasible options, 235/40 R18 and 245/40 R18.

I went through Nokian / Michelin / Conti and it looks like 235 haves more options than 245.

Now he needs to pick one...

 

245/40-18 is not right for that car, why change the tire size? It'll be a little off and the extra width won't help anything. b6/b7 should stick to 235/45-17 and 235/40-18. Perhaps 215/55-16 for snow on dedicated wheels.

I lived in NNJ/NYC in a condo with no possibility for tire storage and my audi was completely fine locally and on new england drives ok on fresh all-seasons driven carefully. Softer "real" snow tires would be overkill, but nokian "all-weather" H or V-rated may be the best choice (as long as they don't wear down quickly in the warm).

 

Given the same thread pattern and compound, narrower tries are better in snow slush, mud and rain than wider tires... and will have less hydroplaning.

In my opinion anything beyond 235 is too wide for that car and with 235 it is already low profile. Not good for NJ/NYC pot holes and bad roads.

There are several good ultra/ high performance all season that you can consider... My recommendation for 235/45/R17 would be
1. Michelin Pilot Exalto A/S ( expensive, 170 a piece .. but you get what you pay for)
2. Continental ExtremeContact DWS (biggest bang for your money with 117 a piece)
3. Overview | Specs | Warranty | Reviews | Test Results | Survey Results
Kumho Ecsta ASX ( good.. but looks some what narrow)

The above tires are more than adequate for the amount of winter NJ/NYC roads see every year giving you good tracking all year round for spirited driving. Again sensible winter driving is needed and mandatory.

If you were up north, had room for storage my recommendation would be different. I speak from my experience of more than 16 years of Canadian winter driving condition through the narrow mountains and highways of Quebec.

Please note that your car is pig heavy... so my strong recommendation would be to get dedicated winter tires if possible and I 2nd nokian. Drive safe.

 

I will also add that the 17" Michelin's are quieter than anything else listed on dry roads. I got the all weather, and not the extreme winter only Michelin's, because I do intend to drive them all year.

The 18" Pirelli M&S's were fairly loud on dry roads.
However you end up going, it's a fair amount of cash, so just take your time and talk to folks unless you have to have them on yesterday.

Good luck!

 

We got an inch or so of snow over the weekend and traveled to visit family who got a bit more. My parents live on a dirt road which was covered with packed snow and when we got to their house the driveway had a few inches of untouched snow. The DWS were great, no problems getting in to their house of up their driveway. I DO NOT think the DWS suck!!

Rob

 

I always appreciate it when people close the loop, and I now see that I didn't do that. For whatever it's worth, 4-5 years later, I bought the Continental DWS that many of you recommended. They've been pretty great in all kinds of slush and rain. I've since moved to the west coast and found that they slip just a little in heavy/wet snow, but overall much better in the gunk than the standard all-season ContiPro Contacts they came with. Seem to be able to take a pothole better, too. I haven't seen any sidewall bubbles. Thanks everyone for the thoughtful suggestions.

 

I'll 2nd this. We've got the DWS tire on one of our cars and it's kind of a disaster in the snow. Is it better than a dedicated summer tire? Maybe.

I've ended up buying snow tires/wheels for this past fall. Problem solved.

The Nokian WR would be a strong consideration assuming it's offered in the size you need.

 

If you're looking for a good, all-around snow tire, this is it. I've fitted these to two cars so far and they've been great. Very quiet, good traction and great wear:

 

Great looking set of winter wheels with the Rial Como.

 

Now in clean (but very cold) roads, dedicated tires have any benefit?
In some places can be pretty cold, but doesn't snow as much.