Mark Alexander wrote:
what is would the difference be between a 49x18 on a fixed/free than the same cogs on a 'normal' bike?
Horizontal (the rear or forward facing drop outs) and vertical (the ones which point down): you can only run a fixed if you have horizontal drop outs, since you need to set the chain tension. The programme mentioned above can also be used to calculate the chainstay length for a given gear combination, so theoretically you MIGHT be able to find a chain length that would fit a gearing with vertical drop outs. However, you would have no choice about the gearing, and i find my chain stretches real fast, so it wouldnt fit for long, unless you changed the chain real often. You can run vertical drop outs with fixed if you have an EBB (eccentric bottom bracket) but their arent many of those about, and its primary there so that people can run singlespeed with discs.