On Mon, Nov 3, 2008 at 6:51 PM, Harvey Sachs <hmsachs@verizon.net> wrote:
> Recently the dreaded "Q-factor" reared its ugly head, in a discussion of
> aluminum cotterless cranks. For those few fortunate enough to have been
> shielded from this stuff, "Q" is the width between the pedals. Less is
> supposed to be better. Nah, I don't remember if it is measured from the
> center of the pedal or the inner edge or the outer edge of the crank arm.
> And I don't care.
>
> This issue sort of saddens and amuses me at the same time, because it seems
> to be one of the many areas of bicycle "engineering" that was driven by
> folklore instead of measurement, for decades. along the lines of the
> "importance" of chain tension is friction losses, and the "critical" need to
> minimize chain deflection. It just seems that the field must have been
> really starved for any kind of empirical engineering of the product (as
> opposed to the factory production methods) for a long time.
>
> Now, I'm not the brightest bulb in the chandelier, but I did a little
> experiment one cold day, and it is one you can try if you have snow and
> cross-country skis. Just go ski, and measure the separation of your tracks.
> After all, X-country uses muscles pretty much like riding, and works with
> the same skeleton. My track is at least as wide as the Q on any of my bikes,
> so I quit worrying and enjoyed the ride.
>
> your mileage may vary, but I'm not gonna worry about the Q factor of my
> vintage bikes. As long as the cranks clear the chainstays, of course.
>
> harvey "show me the data" sachs
That last point--"your milage may vary"--is the one to focus on, because the only data you need in order to understand Q is that some people seem to prefer a narrower one, some a wider one, and some are fine with either. I know people who really are more comfortable and ride better with a narrow Q (or tread), as measured between the crank outer surface at pedal hole. I know other people who are uncomfortable and hampered with narrow Q and say "Ahhh" when they get on a wider crank. Me, I seem to be fine either way, but I don't discount the experience of others who've tried it both ways.
Mitch Harris
Little Rock Canyon, Utah, USA