I have a 09 GT with stock chrom wheels. I am going to get a n2nd set of rims, to use with performance tires and replace snow tires on the stock rims(18's). My question is can I get 20's and switch between the 18's in the winter and the 20's during summer without a issues/adjustments or recalibration required?

 

Should not be a problem as long as both sets of tires (18s & 20s) have the same overall diameter. By the way, where you at in Thornton?? I lived in that area for quite a few years.

 

I do that all the time, except mine are track wheels/street wheels (NASA Rocky Mountain, if you're interested). Only issue is the TPMS, will need sensors in the new wheels and have to 'train' or program them to the ECU, once. Otherwise the TPMS sensor goes off every drive, easily 'reset', but still annoying.