When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
You can keep the total diameter the same between the 18/17 & 19/18 by choosing different tire aspect ratios. The computer traction control just needs the rear diameter to be taller than the front diameter (I believe it's 1" difference in stock wheels/tires)