I need to replace my original tires on my 2006 Mini Cooper (non-run flat). I currently have 175/65R15 Continental ContiEcoContact 3. I've read some recommendations about moving to a 205/50 15. What, exactly, will I gain from the different size tire? Which brand/model should I buy? I'm in Texas, where it's summer driving all year round.

 

wider tire with a lower profile. Go with a brand you can afford. Stay away from cheap chinese tires.

 

Generalization -> The wider the tire, the larger your contact patch on the ground, the better the grip.

A 205/50/15 isn't ideal for daily driving. That'll be about a full 1" shorter than stock, so your speedometer will be super optimistic. Check the MINI2 FAQ here for better sizing:

http://www.mini2.com/forum/faq.php?faq=faq_wheels_tyres

A 205/55/15 would be close to stock diameter, but not as popular a size as 205/50 I think. You could also try a 195/55, 185/60. These would be slightly shorter than stock (better accel) but not AS short.

As far as brand and model, you can pick up ideas on here and by perusing a site like tirerack. Figure out if you're looking for a high performance summer tire, or all-season, or what, and go from there.

You might want to think about different wheels too - those stockers are only 5.5" wide so you probably won't want to go wider than a 195 or 205 tire.

 

Wider = better dry cornering feel.

Alex