General Cycling Discussion - how are bikes measured?
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When people say a bike is 16" or 27", what are they talking about?
06-01-08, 02:41 PM
Sixteen and 27 inches would be extreme sizes--16 is tiny and 27 is huge. In that case, I think they're talking about the wheel diameter, which is common in cheap US-market bikes but doesn't really tell you much.
The way bikes are REALLY measured is by frame size, from the center of the bottom bracket (the spindle at the bottom that holds the crankarms) up along the seat tube to either the top of that tube or the center of the top tube, which is the one that runs forward from the seat toward the handlebars.
Most manufacturers now go center to top, I think. In the old days, road bikes were usually center-to-center, but mountain bikes were center-to-top. Road bike measurements typically are given in centimeters (2.54 per inch). Mountain bikes are often expressed in inches, but you'll see them in centimeters sometimes, too.
"Twenty-seven inch" used to be the standard for American road bikes, and referred to the wheel diameter. Those now use "700C" wheels, which are metric and close to the same size, but not interchangeable.
The main measure is the height of the seat tube, from the centre of the bottom bracket to the top of the top tube (or sometimes the centre of the top tube) eg "A".
However, the horizontal length of the frame (top tube length, "B") is also important, so using one "frame size" is not necessarily enough information. You should check both measures when you are buying a bike.
On bikes with a sloping top tube, some manufacturer's report the "effective" seat tube and top tube lengths ("C" and "D").
However, some mountain bikes with sloping top tubes are sized by actual seat tube length "E".
06-01-08, 04:08 PM
Department store/toy store bikes are generally specified by tire size. Real bikes are specified by frame size. http://www.sheldonbrown.com/frame-sizing.html
06-01-08, 08:51 PM
Department store/toy store bikes are generally specified by tire size.
Yes and those wal-mart bikes except for a few are made by and for the chinese communists,they are short and our government allows us to support communism,reagan and all his policies are definately dead.
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