Here is the link to one of AVON tire "ordering" threads over there on GT40s.com. Member Malcom also posted some of the diameter and width sizes. The front and rear tires size/diameter is very close which is good news for those who want to try them.
Thread:
http://www.gt40s.com/forum/showthrea...light=AVON+245
Sizes:
Front:
245/60/15 V, 7 to 8.5,
26.65, 9.88, 8.66,
Rear:
295/50/15, V rated, rim width 8.5 to 10.5 inches,
26.9 inch diametre, 12.2 inch section, 9.84 inch of tread.