I just scored a schwinn crossfit at a yard sale today for $20 I am consider swapping my motor over to it from my Gary Fisher mt bike, but I had a few questions, The schwinn does not seem as solid as my Mamaba, but it is a hybrid, as opposed to full blown mountain bike, one of my concerns is motorizing a bike that won't hold up. Has anyone done a Crossfit, and how do the skinny tires compare to the knobby mountain tires as far as ride and performance with a motor?