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How to measure BB drop and BB height(3 posts)

How to measure BB drop and BB heightkilimanjaro
May 6, 2002 2:22 PM
I am comparing frame geometries online and some manufacture sites list BB drop and some list BB height. I am pretty sure that BB height is from ground to center of BB shell on a built up frame. Is BB drop vertical drop from center of top tube to center of BB shell? Isn't that
cosine( seat tube angle ) * seat tube length c-c
re: How to measure BB drop and BB heightgtx
May 6, 2002 2:29 PM
bb height is a pretty useless measurement--unless everyone measured using the same tires, which they don't (same problem with standover measurements). BB drop is more accurate--it's the drop from a horizontal line between the two axles. Most road bikes have between 7 and 8 cm drop.
Right you are...Nessism
May 6, 2002 5:32 PM
...drop is a much better number to compare. I have a table on 53-55 cm frames and the most common drop figure seems to be 70 mm.

Schwin Paramount 1999 - 65 mm
Lemond, Seven, Waterford, IF, LS, Ritchey, Ibis - 70 mm
Merckx, Derosa, - 72 mm
Mondonico - 73 mm
Richard Sach - 80 mm

Bottom bracket height:
72 mm drop = 26.5 cm BB height (Michelin 700x23C tire)
72 mm drop = 26.7 cm BB height (Conti Grand Prix 700x23c tire)

Ed