This is a quick question about tyre width. I currently use 700 x 20 as I always thought that 'the thinner the faster'. However I entered an event in the Scottish Highlands today (Nairn Challenge) and there were a lot of quick people on some pretty expensive bikes using far wider tyres. Amittely the road surface was a bit gravelly but it was certainly suitable for road bikes. My question is, does tyre width make that much difference to speed due to rolling resistance? And in general, do people change tyres depending on conditions or just stick with the same set regardless?