Often cited as a vital measurement for correctly tuned bicycles is the Q-factor. What precisely is it, though? How does it influence your ride, and how can you change it?
A bicycle is a somewhat flexible mechanism. Nearly every component, including the saddle height and handlebar width, can be changed. You can even select several chains and cassettes to identify a gearing arrangement fit for your taste. The bike's Q-factor, or more precisely its stance width, is one of the most difficult measures to adjust appropriately nonetheless.
We shall define the Q-factor, its significance, the results of a wrong Q-factor, and how to fix it in the following parts.
What is Q-factor on a bike and why is it important?
The lateral distance across the two crank arms between their outer edges is the Q-factor. This is a feature of the crankset on your bike; several companies have Q-factor listed on their websites. Technically, thus, you cannot alter the Q-factor without altering the crankset.
Often, when talking about Q-factor, people refer to the stance width. This is your pedaling lateral distance between your feet. It considers your foot placement on the pedals, the pedals' form and dimensions, and the length of the pedal spindles.
Your stance width can be changed; this will be covered below. Getting the ideal stance width for your physique will improve pedaling efficiency, lower injury risk, and stop your heels from rubbing on the crank arms or chainstays.
Q-factor influences not simply your pedaling technique. A larger Q-factor lets you lean the bike into a corner farther without running the danger of the pedal contacting the ground.
Stance width is the result of the crank arm Q-factor mixed with the pedal spindle length
How does Q-factor affect your pedaling?
Imagine walking with your feet widely apart; a bike's wide Q-factor provides a similar effect. Your muscles may perform in odd ways, and your feet may become less mechanically efficient when they are too far apart, hence maybe resulting in muscle or joint problems.
Your natural off-bike stance width offers direction on the breadth of your bike pedal arrangement
About ten years ago, Dr. Xavier Disley of the University of Birmingham conducted studies demonstrating that pedaling is more efficient using smaller Q-fact values than larger ones. A smaller Q-factor may potentially have a little aerodynamic benefit.
The stance angle is another similar idea; it is the angle formed by your lower limbs pedaling. This should ideally reflect your natural walkable orientation. Usually, a bike fitting is figuring your natural stance width off the bike and then modifying your bike's configuration to meet it.
In the knees particularly, but also occasionally in the feet or hips, an improper Q-factor might cause pain.
Leg pain and misplaced leg joints can follow from a wrong stance width
Q-factors on Different Types of Bikes
A splay to the crank will lead to an increased Q-factor
Generally with smaller bottom brackets and straightener crank arms, road bikes and gravel bikes have a Q-factor of about 148mm. By contrast, most mountain bikes have a larger Q-factor—about 170mm. This results from longer crank arms and a longer crank axle that permits clearance with the larger mountain bike tires.
To fit their big tires, fat bikes have an even more broad Q-factor—often about 235mm—which can greatly impact pedaling efficiency.
A larger Q-factor results from many electric bikes with mid-mounted motors being wider than conventional cranksets. Companies like Rotor provide reduced Q-factor cranks that more closely match non-electric mountain bikes in order to combat this. Their eKapic cranks for Bosch motors, for instance, have a 171mm Q-factor.
While Bosch's Performance Line SX lowers it further to 160mm, newer electric bike motors like Shimano's EP6 and EP8 series are made to be thinner, allowing a Q-factor closer to a conventional mountain bike at 177mm.
A bike's Q-factor does not change with frame size; the same crank model fits all frame sizes, so preserving a constant Q-factor even if the crank arms are longer. Like those from Frog, high-quality children's bikes can feature cranks with a reduced Q-factor to fit tiny riders more precisely. To increase aerodynamics, track bikes also have reduced Q-fact than road cycles.
What Should My Q-factor Be?
Your anatomy—especially the width of your pelvis—probably determines your perfect Q-factor. Although most riders can adjust to a Q-factor not exactly fit for them, during the pedal stroke this may misalign the knees with the hips and ankles.
Your Q-factor may be excessively wide if your knees migrate inward. On the other hand, if they move outward, it could be too thin. But this could also come from a wrong saddle height; hence, it's important to verify it first before changing your Q-factor.
Taller persons may have to change their Q-factor since their natural stance width is generally greater than that of shorter ones. Including the Q-factor, a professional bike fitting should consider all elements influencing your pedaling comfort and efficiency.
Your anatomy—especially the width of your pelvis—probably determines your perfect Q-factor. Although most riders can adjust to a Q-factor not exactly fit for them, during the pedal stroke this may misalign the knees with the hips and ankles.
Your Q-factor may be excessively wide if your knees migrate inward. On the other hand, if they move outward, it could be too thin. But this could also come from a wrong saddle height; hence, it's important to verify it first before changing your Q-factor.
Taller persons may have to change their Q-factor since their natural stance width is generally greater than that of shorter ones. Including the Q-factor, a professional bike fitting should consider all elements influencing your pedaling comfort and efficiency.
Your Q-factor should inform a bike fit
How Do I Change My Q-factor?
There are several methods to adjust your Q-factor if you feel your current setup isn't quite right:
- Most bicycle cleats and their matching pedal systems let you make some inboard/outboard adjustments, therefore altering the distance between your feet. For instance, Shimano SPD-SL road cleats let 6mm of lateral mobility per cleat, which lets you change your feet either further apart or closer together
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Adding spacer washers to the pedal spindles will increase your Q-factor by one to three mm. Be careful though; this lowers the crankarm's pedal thread count, which can cause stripping—a possibly expensive error.
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Some pedals feature longer axles if your cleats do not offer adequate adjustment. For instance, 4mm longer axles are found on Shimano Dura-Ace and Ultegra road pedals.
- Threads inside for the pedals and screw spanks into your cranks. Usually adding around 20mm to each pedal axle, they greatly expand your stance. This could, however, increase the angular leverage on the crank arms and run the danger of stripping the crank threads.
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Purchase a Wider Q-factor Cranket** here Although most cranksets feature a standard Q-factor, some—like Rotor's Aldhu crankset—offer several Q-factor choices—147mm and 152mm. Although this approach is more costly, for people with serious issues like knee discomfort, it could offer the most important change.
By understanding and adjusting your Q-factor, you can significantly improve your comfort, efficiency, and overall cycling experience.
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