JT - yes, the Karma wheels are a better design and sturdier imo.

Scott - Old habits die hard. I still use mntn bike tires on 26" wheels. I'm probably off-road in my chair 2-3 days a week. Haven't bent any wheels but the torque of the push still shows pretty good side flex on every set of rims I've tried. Maybe given that my x-core's were 26" as well may have something to do with my experience.

To each his own. Whatever works.