Well I hate for my first post here to be on such a controversial topic. I have noticed a couple of threads on here about tire size during my lurking and hope to clear things up a bit or muddy the water depending on you view. Their are two separate issues here regarding tires. One, is changing the rim size, the other is changing overall diameter. To the extend that a new rim does not hit the brake caliper, there would be no adverse effect to changing a rim size if overall tire diameter remains the same. The result of which could mean losing some unsprung weight, losing unsprung weight could improve 0-60, however it should be noted the same effect could be had going with a lighter stock size rim.