Unverferth sells them but if it is price that you are shopping they will not be cheaper.
Each of the 3 tire types requires a compatible rim type; R1 tire must be mounted on R1 rim, R2 on R2, et cetera.
//greg//
True but in many cases on these smaller units they may not have the specs already to build, and depending on distance from them freight can be spendy. I have seen it both ways, rarely though have I seen their wheel components cheaper in price (before markup) than the oem but man they build a super stout and reliable product always well worth the invenstment as far as quality is concerned.
oops am having problems here was trying to respond to Rickb's post. My bad if confusing