After I got my AX1 I was thinking about getting decent tires. Unfortunately the AX1 has the same rare dimensions as the NX250, expensive and not available in modern rubber compounds. With my NX250 I solved the problem by adapting larger wheels (21/17 inch). Disadvantage of this approach: the seat height (especially with stronger shock/front springs) is getting strenuous.
Since the AX1 is already more street oriented why not trying some street tires with smaller diameter?
First approach: wheels from the Kawasaki 250 Ninja. The front rim fits with a El250 (260mm) disk and a XR650L break caliper. Unfortunately the hub of the Ninja wheel must be grinded off 6mm in order to get it centered in the AX1 / NX250 fork. And that would make hard if not impossible to get it past the German TüV – a pity though, I really like the design of the Ninja wheels.
Second try: a front wheel from a Kreidler DD125 “Sumo”, size 2.50-17. This wheel fits plugandplay, so I mounted it on my NX250 (the AX1 is not ready yet), that explains the large front fender. First road tests are promising – but I got stronger front springs and a shorter shock from a NTV650 (which works very nice in the NX250, by the way).
Because you have to keep in mind that the NX250 has already an extremely short wheelbase (1,35m / 53.1 in) and trail (89mm / 3.5 in). So if lowered only in front, the trail gets even shorter and it can get really unstable at higher speed, even dangerous
(believe me, no fun). To account for that, a smaller rear tire (eg 120/80 16) or a shorter shock is a must.