I found an f18 site that quoted mains wheels at 30 inch. likai says the mains are 126 mm dia x 5.75 scale on c/d = 724 mm / 25.4 mm = 28.5 inch if you pump the tyres up to 128 mm x 5.75 = 736 mm / 25.4 mm = 28.97 inch pump to 130 mm and scales out to 29.4 inch. i'm gonna buy one and the tyre size wont bother me one bit likai