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What is the conversion of a (XL) frame to it's measurement in inches?

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Whatever they want it to be. Bike sizes are not particularly well standardized. – Daniel R Hicks Jun 21 '14 at 3:37

It depends on the particular frame - XL doesn't mean a specific size. Also, even for frames labeled as the same size number (say 23" or something), thats only one measurement to summarize the size of the bike - there are many more which can make a bike fit or not - top tube length, stand over height, etc.


(Look at all of the quantities labeled on the figure, courtesy of Trek).

The two most important though are top tube length (E) and standover height (B?).

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I hope standover height is actually B, it's hard to be sure. – Móż Jun 21 '14 at 7:19
I think L is standover height in that diagram. – jbuk Jun 21 '14 at 10:53
Yeah, B is "frame size", more or less. From the top of the seat tube to the centerline of the BB is one way to measure it, though others measure from the top tube junction to the bottom of the BB, along the seat tube. – Daniel R Hicks Jun 21 '14 at 13:57
(It should be noted that the conventional "frame size" measure has become a poor one as slanted top tubes have become more common.) – Daniel R Hicks Jun 21 '14 at 13:59
Looks like A is BB to top of seat clamp and B is BB to top tube, but that's not a great diagram. – Nuі Jun 22 '14 at 2:20

It depends on the manufacturer so you'll need to check the frame geometry specs. Even frames sized in inches or centimeters are not all the same, since different manufacturers measure between different points to describe frame size. There's usually a diagram on the frame spec page defining the different measurements.

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