Are your pedaling like a Merckx or paddling like a Mallard ? Are you sitting on a bike or a barrel ?
If the Q Factor really matters, how come nobody talks about it ?
Good questions.

 Recently we`ve noticed that some cranks are too wide between the pedal holes, placing your feet to far apart. We didnt come up with this idea out of thin air, but from riding assorted cranks, and feeling right on some, wrong on others.
 So we measured the distance between the outside of the cranks at the pedal hole, and called it "Q".
 There are exceptions, but the rule is this: Single chainwheel cranks have narrower Qs than
 If your frame is too wide     fig.1
 at either point, many good
 cranks wont fit !
doubles, which are narrower than triples; and cold-forged cranks have thinner arms, and consequently tend to have narrower Qs than hot forged cranks. Melt-forged, or pressure-cast cranks generally have the thickest arms and the widest Qs.
 To measure Q, mark a line (with tape or pen) on the front middle of the seat tube, or the the back middle of the down tube, then measure from that point to the outside of each crankarm.
 The narrowest track cranks measure 128mm or so, the widest mountain bike triples are up around 178mm. Campy Super Record cranks (the old ones), as a reference, are 135mm-137mm.
 "Low profile" cranks tend to have wider Qs than traditional, box-style cranks. (fig 2) Traditional European box-style cranks, consistenly win the low-Q awards.
 Does Q matter ? Well, we think it does. Your foot-to-foot distance matters when you run or jump, your feet fall into place naturally, but when you pedal a bike, you take whatever the cranks provide. Shortlegged riders ride the same Qs as long-legged riders, so, for any given Q, they pedal more bow-legged.
 You can change your bikes Q by changing the BB spindle, the cranks, or both. But its possible
that when you put on a shorter spindle, the inner chainring will hit the chainstay. (see A, fig. 1) This frame dimension isnt standardized, and some frames are just plain wide here.
 Another potential hangup is the crankarms hitting the chainstays. (B, fig. 1) Frame dimensions arent standardized here, either.
 Bridgestone frames are narrower than most at points A and B, so they accommodate cranks with narrow Qs. Since Q affects how your muscles and joints work, we dont sacrifice it for the dubious benefit of maximum mud clearance. (If you have to ride in sticky mud, skinny tires, not fatter frames, are the way to go).
 In the past 5 years Qs have been getting wider and wider to accommodate frames which are increasingly wide at A and B. This widening does not correspond to any change in human physiology, and we offer these 91 Bridgestones as a well-thought out alternative.

For more information on Q factor, read Bicycle Guide, Aug. 90. And for specific Q factor information on Bridgestone bikes, refer to the spec sheets on the back pages.

A typical "low profile" stands higher than a NON "low-pro" cranc !                                              fig.2
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