Have put a lot of miles on a bunch of different SM bikes over the last few years, and my favorite setup so far is a stock 18" rear wheel and a 19" front wheel (19 x 2.15 rear rim laced-up to the front hub). Just a little bit more versatile than dedicated SM wheels. Like having an extra 18" rear wheel and there's a a pretty wide selection of tires available in those sizes, from street to full-on knobbies. Think I might lace-up an 18" front wheel next time though, just so I can run the same tires/tubes front and rear. Have a few extra sets of factory KTM SM wheels and have noticed that there's not much of a market for them. Really don't understand why. Personally, would much rather ride a dirtbike on the street than just about anything else, especially dicing through traffic and riding aggressively/defensively.