Road Cycling - Identifying frame size with eyeball

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PDA
watch
02-27-01, 09:13 PM
I thought I could tell frame sizes by just
eyeballing the distance between the top tube
and the downtube where they meet the fork crown
or steering stem. But I've been looking at
photos of bikes on ebay that kind of surprise
me after reading their owner's descriptions. What
they say the frame is and what it looks like
at the fork crown don't jibe. Sometimes it
is higher, sometimes lower. Is my eyeball
method not reliable or are the sellers
confused? Thanks.

slo

John E
03-01-01, 07:46 AM
1) Camera perspective is tricky. If the bike is shot from the front, the head tube will look taller than in real life.
2) Bottom bracket heights vary. The higher the bottom bracket is off the ground, the longer the head tube will be for a given frame size.
3) Europeans specify center-to-center frame size, whereas Americans tend to use center-to-top. With standard tubes, this is about a 1.5cm difference. With oversize tubes, the disparity can be 2 or 2.5cm.