Road Cycling - Quick frame size question...

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jfk32
06-09-03, 03:13 PM
I have a question about different frame sizes. I know on older bikes frames were measured in inches right? For instance...

Early 1980s Lotus Challenger SX Male 12 speed. 20 inch frame, measured along the seat tube. Tange 900 CR-MO double butted frame tubes. Cromalite 503 fork. Shimano . Sakae SA cranks. Alloy stem, seatpost, handlebars and Araya 27 1 1/4 rims.

That bike has a 20 inch frame. Convert that to cm and thats 50.8 centimeters. Is this a direct correlation to the frame sizes today? Will this bike be similar to a modern 50cm bike?

Thanks,

roadfix
06-09-03, 03:37 PM
No..........a 50cm seat tube will be exactly that, measured from center to center, center to top, or center to top of seat collar.......depending on the manufacturer.
Now, what I don't understand is why MTB frames are still measured in inches, at least in this country. Is it because MTB's originated in the U.S.?
I wish frame measurements can be standardized.
uciflylow
06-09-03, 04:01 PM
I think you almost have to ride them. Not all 54 cm are created equil. You can't fit one model then buy another and expedt it to feel the same.

dexmax
06-09-03, 10:02 PM
Originally posted by jfk32
I have a question about different frame sizes. I know on older bikes frames were measured in inches right? For instance...

Early 1980s Lotus Challenger SX Male 12 speed. 20 inch frame, measured along the seat tube. Tange 900 CR-MO double butted frame tubes. Cromalite 503 fork. Shimano . Sakae SA cranks. Alloy stem, seatpost, handlebars and Araya 27 1 1/4 rims.

That bike has a 20 inch frame. Convert that to cm and thats 50.8 centimeters. Is this a direct correlation to the frame sizes today? Will this bike be similar to a modern 50cm bike?

Thanks,

Yes it should be.. but a 50cm frame from one manufacturer may not be exactly 50cm(seattube c-c). thus, on other brands it might be a size bigger or smaller...
FOG
06-10-03, 08:09 AM
For a given seat tube angle, the critical dimensions will be the length of the top tube, which in turn sets the relationship between saddle and handlebars, both height and reach, and whether you can straddle the frame. The length of the seat tube is not a very meaningful number, although it was the value used to size frames.