215/40 on 18s is closer to stock than 225/40. 225/40 is about .2" taller than stock while 215/40 is .1" smaller than stock. also, 215/35 is popular for stretching 18s and getting low

 

how is 215/40 shorter than 225/40? only the tire width is changed not the height

 

First that's so little it really wouldn't make a difference.

Phil the number is 40% of the width and that determines tall your sidewall is.

You this calculator, it makes it easy to see the differences:
http://www.discounttire.com/dtcs/infoTireMath.dos

And then just read all of these. You'll be an expert:
http://www.discounttire.com/dtcs/infoHome.do

 

Sweet info jmgrande, those hartmann wheels are beautiful. Where'd I put my credit card

 

You're welcome. If you're serious haha, use the Achtuning link. I ordered the HRS4 DTM 18" and had continental ExtremeContact DWS mounted (235/40/18).

 

These need to be mounted on my A4 like now, lol.

 

because 215 x .40 is smaller than 225 x .40

 

When I bought my car, it had 18" chrome wheels on it. Being new to Audis, I thought they looked cool. But after getting to know Audis better, I started to hate them. After awhile, the chrome will start to flake off and the rim will no long be able to hold air. This is what happened to me, so I replaced them with a set of RS4 DTMs. Here is a pic of my car with the chrome rims before coilovers and the DTMs.

 

those are the rims i plan on getting..i believe they are the S8 rims.

 

Munzter when I first joined the forum, I saw your DTM's and thought it looked AWESOME! So now I am finally getting them. Are your Hartmanns? I'm getting the new ones they just came out with, they are 8.5 instead of 8.