Hey all, I'm a newbie tuner and trying to figure out what to put in for my summer wheels.
During the winter I run 265x75x16's and in the summer I run 275x55x20's, funny thing is (according to my GPS) it's pretty accurate as-is with no adjustment, but if I do put in the diameter according to a tire size calculator it throws it off a bit more.
Just wondering if I should leave it or what's going on? The stock setting is something like 30.8 while the 20's are 31.9, so there is a noticeable difference there.
Here's the site I'm using:
http://www.miata.net/garage/tirecalc.html
Suggestions/comments?