I was at local riding spot (redwood rd, castro valley, ca) and met a dude who modded his excel rims to be tubless, after popping a couple tubes due to temp and general aggressive riding. This dude mobs the hell out of his motarded xr650r. He says, first strip the rim and seal each spoke from the inside with some sort of adhesive ( forget the exact glue... gorilla of some type?). Then you adhere tape(?) along the inner spine of the rim, over the spoke nipples. I saw him ride without tubes. It works. I dont know how safe or reliable it is. Has anyone heard of such sorcery or have first hand experience? Could shed a few pounds off the pig maybe.