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Bottom Bracket Drop Spreadsheet Calculator

Grant Petersen of Rivendell Bicycle Works sent me an email:

Hi Sheldon,

Here's a neat thing. CPSC used to require (probably still does) that you be able to lean a bike 25 degrees (90 minus 25 is 65) before smacking a pedal. We're working on some bikes-in-boxes, which have to comply, so I need to know the right side Q (aka tread), the pedal width, crank length, tire things.

Andrew Drummond and Bhima Sheridan created this to help me design bikes.

The pedals in the list are the mks pedals we sell--you know them all. I think with clipless, the advantage is even greater.

• T is actual tire width
• R is wheel radius
• QR is right-side Q
• C is crank length
• P1 is crank where pedal enters it, to the part of the dustcap that'll hit first
• P2 is radius of pedal dustcap (13 is typical, no need to fret about this one)
• L is complement of minimum allowable lean angle (25 deg)
• D is bb drop.

To download, control-click, select "Save this link as..."; Select "Source" from the Format menu.

(If you're using a Windows PC, right click the link and choose "Save Target As...",)

bbdrop.xls

Feedback? Questions?

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Since March, 2002

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Updated March 13, 2002

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