I think they just look at the potential market.......in numbers......and there just isn't a lot of call for a 15" M/C tire. These 250, 280 & 300 series tires are being built strictly for the custom market.
If you look at the wheel market, all of the billet guys are starting to cut 18" X 10.5" wheels for HD style axles now........everyone will be running them in a year.............heck look at the 200's........they've only been out about 2 1/2 years..........and they're just a joke now.........I put a 180 on Vickis' Deuce and it look s puny.......
Tim