i've got an 18 speed mountain bike which doesn't have a high enough top gear. i can't get enough speed out of the bike before the gearing reaches its limit.
how can i change this? would a 21 speed bike be better or is it simply the size of the front cog which counts.
if i was to buy another gear set or bike what sort of measurement should i look at which tells me the gearing ratio of the any given bike?