Framebuilders - How to judge frame size?

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peripheral
01-05-06, 03:10 PM
I just recently purchased a used Trek bike from my local bike shop. They said it was a 58cm bike, but it feels smaller than my other road bike which is a 58cm. I think it might be a 56cm. How do you tell? How do you measure it to get those numbers? Thanks for the help!

baxtefer
01-05-06, 03:21 PM
not all frame manufacturers measure "frame size" the same way.
generally a measurement is made along the seat tube from the center of the bottom bracket to either the top of the top tube (center-to-top measurement) or to the center of the intersection of the top tube (center-to-center measurement)

Trek on the other hand (in addition to fuji and some others) measure the entire length of the seat tube from the center of the BB to the top of the seat tube collar. So a 58cm trek is more like a 55cm c-c or so.

The more important measurement though is the top tube length. measured from the center of the seat tube to the center of the head tube, parallel to the ground, along the top tube (assuming a "traditional" non-compact frame witha horizontal top tube)
EJ123
01-05-06, 06:47 PM
The more important measurement though is the top tube length.
Yeah really dude, im 6'3 on a 16.5in. Im use to the small size but I only care for the top tube length.