crank q factor brief explanation

[wapad]

I have read up about this before but I forget exactly

 

i did try a search here but no luck

 

thanks

[Johan Bornman]

Ignore Q-factor. It is a non-issue.

 

The crank's Q-factor is the distance from the one crank to the other or, how far your feet are apart when pedaling. In the gym on a stationary bike you'll feel your feet are slightly wider apart than on your other bikes, but so what.

 

It is difficult to actually measure the Q-factor since the one crank points forward when the other one points backward and getting the measurement from the outside of the one crank to the same point on the other is neigh impossible.

[Chro Mo]

This from Grant Petersen at Rivendell - a great proponent of smaller q-factor - even as far back as the early 80s.

I feel that Q-factor is one of those things that scarcely affect us at all - so agree wiith JB there.

May impact if there are specific injuries involved.

It is a highly subjective issue.

Good explanation below, and even better ones if you read the old Bridgestone catalogues.

 

https://www.rivbike....sults.asp?ID=54

 

 

Q-Factor. Yes, Q-Factor.

It's the distance between the pedals at the outside of the cranks. In other words, it's how far apart the cranks put your feet. Are you walking a tightrope, or giving birth? Pedaling a bicycle or walking like a duck? That's Q (quack)-Factor.

At the turn of the century, this crank dimension was called "tread," a term still adhered to by some. We call it Q-Factor because when "tread" was in vogue, tires were all smooth, and "tread" couldn't possibly have referred to the rubber pattern. But these days, "tread" means rubber pattern, so the discussion can't begin until you dig out of that hole.

In any case, Q varies from about 135 to 180, with most good road double cranks hovering around 140mm, and most mountain bike cranks around 173mm.

With the exception of Ritchey, crank makers do not list Q. Most make high-Q cranks, and would prefer that you not ask. There can be no arguing that a lower Q improves aerodynamics, but a far more compelling and practical reason for attending to your crank's Q is...how it feels.

Some riders are not sensitive to it at all. Others have physiological quirks that make them better off with their feet closer together (low-Q) or farther apart (high-Q) cranks. In general, road riders accustomed to the superb, low-Q professional grade Campy, Zeus, TA, and Stronglight cranks have a harder time adapting to modern cranks with higher Qs. They often hate them, and don't even realize what it is until somebody suggests the Q. On the other hand, riders raised on higher Q cranks often think the whole issue is silly, because they can't tell any difference.

If you're used to a low Q crank and you pedal a bike with a high Q, it's possible that you'll experience pain on the inside of your knees.

Edited July 9, 2012 by Chro Mo

[wapad]

Thanks guys

 

Just that you see it mentioned plenty especially with XX cranks ???

[Stretched@Birth]

Thanks for that bit of info Chro Mo, it's something I've been wondering too, but hadn't taken the time to research. Would have thought that it would have a bigger impact on muscle dynamics than it seems from your post. I'll sleep better tonight, thanks!

[rpedro]

The effect of Q Factor on gross mechanical efficiency and muscular activation in cycling.

Disley BX, Li FX.

 

Source

 

School of Sport and Exercise Sciences, University of Birmingham, Birmingham, UK.

 

Abstract

 

 

Unexplored in scientific literature, Q Factor describes the horizontal width between bicycle pedals and determines where the foot is laterally positioned throughout the pedal stroke. The aim of the study was to determine whether changing Q Factor has a beneficial effect upon cycling efficiency and muscular activation. A total of 24 trained cyclists (11 men, 13 women; VO(2max) 57.5 ml·kg/min ± 6.1) pedaled at 60% of peak power output for 5 min at 90 rpm using Q Factors of 90, 120, 150, and 180 mm. Power output and gas were collected and muscular activity of the gastrocnemius medialis (GM), tibialis anterior (TA), vastus medialis (VM), and vastus lateralis (VL) measured using surface electromyography. There was a significant increase (P < 0.006) in gross mechanical efficiency (GME) for 90 and 120 mm (both 19.38%) compared with 150 and 180 mm (19.09% and 19.05%), representing an increase in external mechanical work performed of approximately 4-5 W (1.5-2.0%) at submaximal power outputs. There was no significant difference in the level of activity or timing of activation of the GM, TA, VM, and VL between Q Factors. Other muscles used in cycling, and possibly an improved application of force during the pedal stroke may play a role in the observed increase in GME with narrower Q Factors.

© 2012 John Wiley & Sons A/S.