Hey all,
I'm looking at buying some new tires from TR. My stock tire size is 205/50R17. I'd like to go lower profile, and maybe wider. How far can I go, and what would be the ramifications of these changes?

Hey all,
I'm looking at buying some new tires from TR. My stock tire size is 205/50R17. I'd like to go lower profile, and maybe wider. How far can I go, and what would be the ramifications of these changes?

OK, here you go. Popular wisdom has it that you shouldn't go over or under by more than 3 % compared to your stock tire size. To help you, I suggest you use this simple and easy tool : http://www.1010tires.com/TireSizeCalculator.asp You'll see what fits and what doesn't.

I too have a 330xi and the stock wheels/tires combo on mine (sport + winter packages) were 7.5 x 18 (front) and 8.5 x 18 (rear) with 225/45/17. I've just got 18" wheels mounted with 235/40/18. With this, I'm still in the recommended sizes/width.

That said, the wider and bigger you go, the more (unsuspended) weight you have to put in motion (for the same wheel/tire combo -- of course, you can choose lighter wheels and tires, but it will probably cost more). That means that your car will accelerate a little bit slower because of the added inertia and that you may have a more heavy feeling steering. The phenomenon is more visible when you put larger wheels. Another downside of bigger wheels is more tramlining (for an explanation, see the following link : http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=47). Finally, one of the biggest differences is that going bigger means reducing the height of your tires sidewalls (the middle number in the tires spec -- for example a 235/40 R18 means 235 mm wide, height = 40 % of the width and outer diameter is 18 inch), thus losing some comfort and making your rims more prone to bending/cracking (beware of this potholes :bigun2).

The good side is that you'll get a better handling car (especially if you choose good quality tires) and a better looking car (which is why most people choose to go bigger).

Very cool. That calculator is really helpful for this. Thanks Cool3!

If you want less tire (smaller profile), go with some 18" or 19" wheels.

Yeah, I've been debating whether to upgrade the wheels. I figure if I'm that neutral about it, I might as well go with the cheaper option, which is to just keep the stock wheels, and get new tires.
Besides, I really like these ones (although they're a pain in the @$$ to clean).