I'm going to order a new front tire, but all I'm finding are bias plys. Currently it has a Marathon M880E, size 80/90-21, which has DOT code 4102 so it's very old. I'm running a Bridgestone Exedra G850 radial on the rear. The BD front wheel is 2.15 x 21, so I think sizing is limited to the 80/90 or a 90/90. Does anyone know if/which brands are available in a narrow 21" radial? I'll likely run the Bridgestone Exedra Maxx or the Avon if I am limited to a bias ply tire.