Way back when, I decided to check what Q factor or tread might be optimum for me. Being a fairly simple sort of empiricist, one winter day I got out the cross-country skis and when out across the field through the snow. Coming back, I measured the ski pathe widths, inside of left to inside of right, and outside of each to the other. That seemed to indicate how wide I wanted my cranks to be (just a smidgen wider than inside-to-inside.
Then, come Spring, I forgot the measurements and got back on the bike to ride. Seemed to work, though. Perhaps a necessary sacrifice to the knee gods? :-)
I suspect that Q matters a great deal to a somewhat smaller proportion of riders than the fraction that worry about it, but that's fine, too.
harvey sachs mcLean va (but did that measuring when we lived in cosmopolitan Cranbury, NJ, population about 2000, and had been for 50 years.)
This business of Q factor is a very interesting one. I have several bikes all deliberately set up with a narrow Q factor. I might add that the Q factor is narrow for me because my femurs are narrowly set in my rather narrow hip structure. When I attach a cycling shoe into the pedals of my bikes I get a measurement of about 5 inches from the center of the pedal (where the shoe and my foot would also be centered) to the center of the downtube. When you double this measurement to account for the other side, you get a total stance width of 10 inches. This 10 inch stance width corresponds to standing upright with the feet parallel and with ten inches between the center of one foot to the center of the other. Correspondingly I measure approximately 10 inches between my femurs as they exit my pelvis. In other words, a narrow Q factor is good for someone with a narrow hip structure, but not neccessarily good for someone with an average width.
I am basically saying that a narrow Q factor is overemphasized for most people who would probably be better off with a wider Q. It is normally said that we are most efficient when bone aligns over bone and strongest when the leg is thrusting directly down from its point of origin to the center of the foot or pedal. Once again we are seeing people swept up in a fashionable marketing stradegy without any regard for their own physical needs.
Some who know my recent drama with Superbe Pro cranks may know that my problem with using a Campy bottom bracket was that it spaced the cranks too far out, messing up chainline and Q factor. I recently found a Sprint spindle that has the same taper as Superbe Pro and am now using it on my Raleigh. The Q factor is reduced by less than a 1/4 of an inch on each side, making the total combined Q factor less than a half inch narrower. I not only can immediately feel the improvement in my cycling but also in my gear shifting. For me this lower Q is a good idea. Your mileage will most likely be different. One need not even say that as you gain body weight, the bone structure of your hips and therefore your Q factor does not change. Getting fatter or getting more muscular really does not change the Q. Your structure does not change much unless you are a woman after your first childbirth, in which case your femurs do exit wider from the hips.
For most of you, I bet your ideal stance is more like 10.5 inches apart and therefore your Q factor should allow for a wider measurement too. Your cycling may improve if you utilize cranks with a wider not narrower Q.
Garth Libre in Miami Fl USA