[leroy17]

I have Goodyear GSD3, 285 40 17 on 10 3/4 rims and I feel that it is a good fit. I confirm that the GSD3's do measure larger than other 285 40's.
There are also a number of topics on the mustang and Corvette forums about Sumitomos measuring smaller and GSD3's measuring larger. These forums have side by side photos and also fitment photos which clearly show the GSD3 is a larger tyre in width and diameter whilst still being the same 'size'.
I have some links and photos which I can post up later.... hope that this helps.

I went for the 285 40 17 for the increased side wall height to 'fill' the guards a little better. This is purly a visual aspect which was noticable as I then had a clearance issue with my exhaust which runs down the side then in the rear wheel arch.