Favero Assioma DUO-Shi Q-Factor
Favero Assioma's are considered to be one of the most accurate and reliable power meters on the market but with the release of the Favero Assioma DUO-Shi there has been lots of discussion on the addition of 64-65mm to the q-factor compared to the more common 53-54mm addition. That's a difference of 11mm but do you know what the q-factor is on all of the bicycles that you ride and the addition to the q-factor by the pedals on those bicycles? Keep reading to dive deeper into q-factors...
The q-factor is a term used to describe a crankset’s width, measured in millimeters at the outside edges of the assembled crankarms. This value typically ranges between 147 and 223mm, and is a function of the crank spindle length, bottom bracket width/type, and chainstay specifications to ensure proper chain-line relative to tire dimensions and rear hub spacing.
Road, touring, and gravel bikes q-factor widths range between 145-157mm, cylocross 155-157mm, MTC-XC 156-157mm, MTB-DH 183-193mm, Fat 170 202-213mm, Fat 190 203-233mm. Roughly speaking, the q-factor tends to be about 150mm for a road bike and 170mm for a mountain bikes.
Larger tires require wider chainstays; wider chainstays require increased hub spacing, bottom bracket width, and crankset q-factor.
The important point to remember is that the q-factor plus the addition of the distance to the center of the pedal bodies are mapping the center of the pedals onto a cyclists stance width and many cyclists might actually be riding bicycles where their stance width maps onto pedals with centers 195mm - 291mm apart. Ultimately our mapping is a function the q-factor plus pedals, pedal spindle length, cleat choices and how we mount cleats to shoes.
The distance that works best for each of us is actually a function of optimizing pedaling efficiency and avoiding knee adduction moments that can cause acute pain or injury. Fortunately, there's actually a stance width range that our bodies are able to comfortably operate in and believe or not our bodies adapt to the width we ride most frequently as long as that range falls within our personal min-max stance width measurement. This means that if you switch from a bike configuration that requires a narrower stance width to a bike with a very wide stance width it will take 2 to 6 weeks to train your muscles to achieve optimal performance. Put another way if you train on a fat bike for several months and then switch to a road bike you will lose some of that hard won leg fitness until you adapt to the muscle recruitment pattern of the narrower pedaling base and vice versa.
Finding the right stance width ranges for your body type and riding style not only helps improve stability and pedaling efficiency, but it can also help avoid injury.
With the above points in mind, Favero's conclusion that there is no absolute rules on relationship between q-factors and ideal stance widths makes a lot of sense. To develop an accurate understanding, the best thing to do is to consult an experienced professional bike fitter to determine a stance width range, take stock of your crankset q-factors, then add in the published q-factor additions published by pedal manufacturers. The results might be surprising.
If +64-65mm is problem there's always the standard assioma duos that have been acclaimed and loved by many for years. They add a more conventional +54mm to the q-factor and are compatible with the original LOOK Kéo cleats.