frame size

dominicg

Just out of interest can anyone tell me why size 58 Trek actually measures 55.5 C-T? When I went to buy a Ribble and said what I was on they looked surprised and said I should be on a 55. And they were right- I'm very comfy on my Sportive, except that when I went home and, out of interest, measured my Trek, I found I'd been riding one all the time! It doesn't matter in a way because I was always going to get the Ribble anyway but why would Trek label a bike bigger than it actually is? I did ask Trek the same question but they seem highly selective in the questions they answer. Cheers, Dominic

smidsy

Manufacturers use different methods to measure their bikes - that is why you will often need a different size between makes. Then there is the different frame styles which measure differently too.

It is also why noone can ever say you need a 56 - bike sizes are not labelled like a suit - a 40r suit is a 40r suit wherever you get it from - a 56 bike can be many different things depending on where you get it from.

dominicg

Yes I take your point, and before you go near a frame you need to look at all that geometry as you want to have a good idea of how relaxed or otherwise you might be on it, but I just thought it a bit odd as I expect most people would regard the quoted frame size to be based on C-T (or C-C I suppose). I've certainly not seen any suggestion that Trek sizes don't follow that "rule".