Sometimes it actually has to do with the surfaces you are riding on the majority of the time. WHen it comes to hardpack riding, less is often more. The automatic response to a loss of grip is to go with bigger knobs on the tyres, but this, combined with a thin sidewall often makes things far worse, as the tyres tend to squirm under pressure (especially if you fall comfortably in the Buffalo cat like me!). On Cascades single track, I have actually found that a lower profile rounded front tyre works better than the aggressive Nobby Nics by miles!
