Bicycle Mechanics - bb q factor and knees
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06-14-06, 01:00 PM
My commuter bike is a mountain-style setup with drop bars (I also have a road bike and a fixed gear). I keep my bikes set up pretty much identical in terms of saddle height and drop/reach to the bars and I use SPD pedals with the same shoes with all three. I've noticed that my knees tend to bug me a little more when I ride the commuter. Could the difference in bb width have anything to do with it or am I just nuts?
06-14-06, 02:49 PM
Q could affect this, as could geometry (especially saddle position in relation to BB/BB height) and crank length
06-14-06, 11:04 PM
Gearing is a factor in feel as well (loading of the knees). I have not personally observed very much effect on Q factor so much as read about it, and I have somwhere in the order of 10 bikes, and periodic knee probs). If the difference is dramatic( like 6-10 mm) I could see it as a factor, otherwise I would look at saddle fore-aft position in relation to knee-over-pedal measurements.
The lax mountain bike geometry could possibly be putting your knees too far behind the pedals during the revolution. Try scooting your saddle forward, or better yet, check how your knee lines up with the pedals on your road bike and mimic that setup on your mtn bike.
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