Thats because "race" cars go into a corner at a high rate of speed and need all the contact they can get to the pavement when making a turn. This helps keep it from flying off the track, but it certainly doesn't make it corner better. The best way to describe it would be to drive a B5 A4 or S4 then drive a B6 A4 or S4 with wider tires stock and you can feel the difference making a corner. I have developed the "feel" of it because i have literally driven every audi ever manufactured.
Have you ever been on roller blades, and a skate with four flat wheels? Which one do you think is easier to corner on? Easiest way i can explain it.

 

Thanks again folks.

"Thats because "race" cars go into a corner at a high rate of speed and need all the contact they can get to the pavement when making a turn. This helps keep it from flying off the track,

I always perceived that as better handling and a desired affect.

When I say I want to go wider for a better looking footprint, that does not mean "too wide". It means I want to get the most out of whats out there and available and yet stays within the boundaries of proper form, fit and function.
I'll exhaust my research, take in all the advice, make a decision and be happy with it the first time.
In any case, anything I put on it would certaintly suffice for the way I will drive the car.
Interested in knowing if anyone has gone with a 9 or 9.5 and what they think of it. It just might be too wide.
My thought is if respectable wheel manufacturers are making them for a specific vehicle and respectable tire/wheel places are putting them on, then I assume it's all approved and safe. Could be a bad assumption.

"may i show you the 225/40ZR18's on 18x8.5 wheels?"

Yes would love to see it. Sometimes the right setup gives the right or better appearance.

 

what's your budget? that's going to make the largest impact on what's available to you. my A6 has Hartmann B7 RS4 wheels, and i'd look to put them on again, but they are pricey. same goes for tires, i run kuhmo ecsta SPT's. they are not the top rated tire (though they are rated highly), but for daily driving they are the best bang for the buck. are you looking for warm weather performance, or all weather performance? runflat? smooth ride or aggressive response?

 

Hey ml...what size are those?

This is where I'm at. I am going to want new tires soon. Not so much need. More along the lines of beginning modifications to the car. While I am going to spend the money it is worth looking into wheel sizes before I go and buy tires.
From constant reading I have decided to stay with 18's. Happy medium I read with 17's being ideal, 19's being too much.
I am down south so looking for all performance, not worried about weather at all as this also is not my only vehicle.

After I'm done with wheel/tire choice I am going to look into the possibility of unaggressive lowering and upgraded sway bars.

After that I will look into horsepower upgrades.

Notes: Paper work for my car says 18 x 8. When I measure I get 8.5. Not sure where they measure from but I measured the widest point. Would hate to buy 8.5 and think I'm getting an upgrade only to find no difference. Looking into 18 x 9. I know it's not much but it's something. Couldn't find a 18 x 9 until someone posted about discount tire.
You know, if all the ponies don't fall into place I'm fine with that. I'll just keep my wheels and move on. Lowering it some tends to take some of the undersized look out of it anyway. Just want to see the options. After all, being stuck with 8.5's is not a horrible thing.
LOVE THIS CAR.

 

they are 18x8.5 with 225/40ZR18's. They are the 35mm offset hartmanns, and 235/40's will rub the steering knuckle. the 42mm offset hartmanns would cure the problem, but they were on the car when i bought it. hence the 12.5mm h&r trak+ spacers on my wishlist.

oh, and you measure inside edge to inside edge at the beadseal

 

If the rims are OEM you do not have 8.5s. The 05 A6 came with the following rim choices 16X7.5, 17X 7.5 or 18 X 8. The later year S6s with the V10 came with either a 18X8.5 or a 19X9. Because of the similarities in wheel wells between the C6 and the A6 you could probably get a 9 inch wide rim to fit on your 05 4.2.

The stock tire on the 05 with the 18X8 rim was a 245. Unfortunately the wheel well will not take a tire wider than a 265. Since you can get a 255 on the OEM 18X8 rims, the 8.5 or 9 inch rims are only going to allow you to increase the width of your "footprint" by 10 mm or approximately a 1/4 of an inch. Since you can enjoy half of the available increase in "footprint" size by sticking with the stock rims I would save your money and just mount the 255s on your current rims.

If you just want to get new rims for a better look, take a look at the Hartmann website. I recently picked up a nice set of rims for my 05 4.2. After driving the OEM rims for the last 4 years I wanted a new look and did not want to keep mounting and dismounting my summer and winter tires on the same set of rims.

 

Very good. Thank you Kevin and ml.
Got it. Doesn't seem worth it at all to change them and that's what I wanted to know.