I just ordered the 285s all around from The Tire Rack. According to the tire specs listed there, the 285s are .5" NARROWER than the OEM 275 F1s for tread width. The section width of the 285s is slightly more when mounted on the same size rim but the tread width is not. Go figure!! :shrug:
I had trouble believing that the GS D-3 285s were narrower than the OEM F1 275s, so I checked Goodyear's site. The 285s are listed there as being about .2" WIDER than the 275s. Maybe somebody who has had both mounted on the stock 9" rim will chime in with some input.