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Measuring the size of a bicycle?

Old 02-01-08, 09:33 AM
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foehn
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Measuring the size of a bicycle?

Your help, Please!

How do I measure a bycycle frame to state what size it is?

Do I measure from the center of the top tube to the center of the bottom bracket or do I measure OR
the bottom of the top tube to the top of the bottom bracket or. . .

How exactly do I do it?

Thanks,

foehn
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Old 02-01-08, 09:45 AM
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It depends on the manufacturer, but the more traditional way is from the center of the bottom bracket to the center of the top tube. Some manufacturers today, however, measure from the center of the bottom bracket to the top of the top tube. Others measure to the top of the seat tube, some go by the top tube length (center of head tube to center of seat tube) and some even go by effective sizes (where the tube would be if it was traditional geometry)
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Old 02-01-08, 09:51 AM
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I'd measure both center of bottom bracket to center of seat tube/top tube intersection (ST c-c) and center of BB to top of ST (ST c-t). (Both along the ST of course.) That's more likely to be the manufacturer's stated size, but a better measurement is center of seat tube to center of head tube (at the TT if it is a traditional top tube [c-c TT length] or along a line parallel to the ground beginning at the head tube/top tube intersection and ending at the seat post for a frame with a sloping top tube [c-c effective TT length]).
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Old 02-01-08, 10:24 AM
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If you want to know a size in order to include that info in a sale, then the most universally useful info for might be seat tube c-c and also the standover height. If this is very cool bike then it probably is smart to include other info, at the very least the top tube length.

If you want to know about sizing to buy a bike, then keep in mind that the numbers only get you in the ballpark for fit, it really pays to actually ride the thing and see how well it fits.

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Old 02-01-08, 11:21 AM
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Virtual top tube measurement(on compact frames) and real top tube on traditional frames is the most important measurement for me. Standover being second and seapost center of the crank to the top of the seatpost. Alos on small frames what wheel size is used. Good luck.
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Old 02-01-08, 11:59 AM
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Originally Posted by JiveTurkey View Post
I'd measure both center of bottom bracket to center of seat tube/top tube intersection (ST c-c) and center of BB to top of ST (ST c-t). (Both along the ST of course.) That's more likely to be the manufacturer's stated size, but a better measurement is center of seat tube to center of head tube (at the TT if it is a traditional top tube [c-c TT length] or along a line parallel to the ground beginning at the head tube/top tube intersection and ending at the seat post for a frame with a sloping top tube [c-c effective TT length]).
+1
Jive Turkey said it right.
The most common nominal sizing for marketing purposes is c-t, from center of bottom bracket to top of seat tube.
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Old 02-02-08, 12:50 PM
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What are you stating the size for? To sell it? Then be clear about how you measured it as well as the result.

It might also be possible to find a geometry chart for the frame and link to that in the ad.
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