For the front seat it doesn't matter, as the mounting height is approx the same regardless of wheel size. Between 559 and 622, I've never experienced a noticeable difference for the rear. Either way it feels tippy and top heavy, and makes loading/unloading a nervy affair. I will say that dropping down to 406 provides a significant improvement in riding quality. Loading was way more reassuring too, but that might have been as much to do with the super duty kickstand support. Of course neither hold a candle to the stability of long john style bikes.