chillyuk said:
As a rough rule of thumb I was always taught that the inside leg measurement less ten inches as a starting point for frame size. I have a 29 inside leg, and a 19 inch frame does me nicely.
Does this no longer apply with modern frame geometry.
I dont know, since Ive only recently bought bikes. But your way of doing it is probably as valid as a starting point for guessing size as any other.
I have seen a couple of formula's (recommended by someone on here forget the username though) for working out ballpark figures. They matched up pretty close, within 4cm for me, so it gave a small range of sizes to try to see which fit best.
Also the top tube length is important. You can alter seat height dramatically easily, but you have limited alteration to your reach (saddle slide and stem pretty much) and it will effect handling to put on shorter or longer stems etc. So its important to make sure your reach is good to go.
MrMonster said:
Robert, the only local bike shop I know of in my town is Halfords, will they do this?
They should size you, but its dependant on staff's skill level how well they do this, halfords dont have a good rep. I doubt they would put you on a turbo trainer and spend time setting bikes up for you perfectly to see how you feel on them.
Id travel a bit further to a better bike shop for important technical input if possible.
