Originally Posted by Geezer
The stock class guys are pretty much stuck with wheels the same size as stockers (14x6 and 15X6 for 1st or 2nd gen Miata). Fortunately the stock wheels on a Miata are pretty light compared to other cars. Seems like the most popular tire size is 205/55-14 but some will squeeze a 225/50-14 (Hoosier A6) on them (and yes, both have very stiff sidewalls). More and more people are using the 15's because of the much larger tire selection (and sometimes lower tire prices) and accepting the increased weight. But yep, once in street prepared the guys are cramming huge tires (aka wide) on equally wide but smaller diameter rims. I like to call them cartoon tires as they look like something you'd see drawn in a caricature or the comics.
Ive got a question for you. What is the contact area for a 16" vs a 15" of the same width and aspect ratio? Do you think its actually the same?