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Crank Arm Angle

Crank Arm Angle

Crank Arm Angle

Hi, for a 3 piece crank is the angle (or taper) the same for any length of crank arm?

Ex. If you where standing on the bike and was looking down at the right hand crank arm, you will see the crank arm going out at a angle to miss the chain stay.  Would a smaller crank arm follow the same angled path or the shorter the arm would result in a different angle?  Take a crank arm length of 180mm to 150mm.


RE: Crank Arm Angle

In the bike industry that angle is call "Q-factor".  I think that name was coined by Tom Ritchey if my memory serves me.  It would be the same from one cranks size to the next providing they use the same brand and same bottom bracket length.

Why do you need to know they info?

FYI - it's not that angle that provents the crank arm from hitting the frame it's really the bottom bracket spindle length that you should be concerned with.  Also, if your bike has front chain rings make sure your chain line is correct.

Here is a link for everything bike related:


Best Regards,

Sr. Mechanical Engineer
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