I've noticed variations too. i always think is funny but never really worried about it. I chalk it up to taking the inside line on some curves, even subtle curves like up hills etc. sometimes I go back and forth to get up them. you should try marking the ground with chalk and riding he EXACT same line each time each way and see what the computer says ... hahaha. oh I just the read the post before mine .... hahahaha duh ... what he said