30.9 millimetres = 1.21653543 inches
You know, I understand the imperial/metric situation, but how on Earth did we end up with the situation where there are just so many different seat-post sizes?
Or is that just a 'metricated' version of 1.2" in this particular case?
Surely tube manufacturers like Reynolds et al, if they have been making tube-sets specifically for bicycles for years, would have benefited from using just a few standard, more rounded sizes than the plethora that exist now?
Edit: Doh. I found out, and it's pretty obvious now I think about it - it's all because the seatpost has to fit down the *inside* diameter of the seat tube, which can vary because of the different buttings etc. used over the years as tubing has evolved.
