Any issue's with moving up to 225/40-18's on the stock 18X7 rims? I'd like to take advantage of lower pricing and selection compared to the stock 215X40-18's. I assume the 2.2% increase in overall tire diameter is within the acceptable range for computer functions. Warranty concern at all?

theres not much of a difference between a 215 and a 225. i dont think its enough for you to rub. thats considering if your car is at stock height.

i use to put 225s on my 16x7. no problems at all.

I think someone here posted this for me when I had questions about fitments. I found it very helpful. Hope it'll do the same for you. I think 225 should be just fine.

http://www.rimsntires.com/rt_specs.jsp

Actually my next set would be the 225/40 too because of pricing and availability. I don't think you'll have any warranty issues.

Let's just put it this way... I can fit 255s under my car and only have an issue when I'm in full wheel lock. You have to find the "sweet tire" size that will work best for your car. From a 215 to a 225 though, there should be very few, if any issues.

I'm running 225/45/18 on the OEM MS3 wheels without any problems at all. 225/40 on a larger wheel will for sure be fine.

I don't think anyone posted this yet, so here goes.

225/40/18 and 215/45/18 are the same height on the sidewall, and difference of 10mm in width, you'll never know the difference. On my old GTI for 4 weeks I ran 3 225/40/18 and 1 215/40/18 while i was waiting for a tire to get shipped. Not only did I never feel a difference on the road, I never felt the difference on cornering either.