Norm Peterson
corner barstool sitter
He threw some screwy reason out, but I really do believe that he was unwilling to do any "dealer-installed" work prior to delivery.Perhaps your dealer had to go by what options were available for an "08" GT coupe when ordering would be my guess?
9.5" is only the measuring width for this size. Nothing more should be inferred.I also noticed the slight bulge from the images and can't quite understand how a 265/40-18 tire would have any bulge at all when mounted on a 18x9.5" wheel with 45mm offset?
A Michelin PSS tire in 265/40-18 is listed as being 10.7" wide on a 9.5" wheel. A 9.5" wheel is 9.5 inches between the bad seats, which are on the insides of the wheel flanges. Add half an inch (typical) for each flange and you only have 10.5".
"Optimal" depends on what you want to optimize. Which could be either a single aspect of tire behavior or some "best overall average" of a combination of conflicting characteristics. Handling crispness and steering precision tend to get better with wheels slightly wider than "measuring width", but ride quality and launch bite tend to be better down at measuring width and narrower. Appearance is a strictly subjective aspect that doesn't even have a definition of 'optimum'.According to TireRack and Discount Tire specs, the optimal tire size for a 18x9.5" wheel with 45mm offset is 275/40-18.
Looks like you've also got a bigger straightline traction requirement to meet.
Thanks. That year GT500 wheel is one of only a few wheels that I feel that an OE mfr ever really got right. It's probably why I went with the 7 split spoke design in Forgestar when I went to the 11" wides. Both appear to have evolved away a bit from the split-spoke design Cosmic wheels of the early 1970's for sports roadsters and compact cars, and I always did like those.On a lighter note, the GT500 wheels definitely look really awesome on your "08" GT coupe
Norm