Sheldon Brown's Bicycle Glossary Q

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Q-factor In Fit-Kit © terminology, this is a factor based on the relative length of the femur compared to the rest of the leg. A large Q-factor is interpreted as an indication that the rider in question needs a frame with a shallower seat tube angle. Also, another name for the tread of a crank set. Grant Petersen originated this usage in 1991

Quadrant Shifter

An obsolete Sturmey-Archer shift lever that mounted on the top tube of the frame. Surplanted by the handlebar-mounted trigger shifter sometime before WWII.

Quadruple Butted

Buttedto four different thicknesses, including the thin section.

Quadruplet, Quad

A tandem for four riders.

Quick-release Wheels

Quick Release wheels use a cam mechanism to allow the wheels to be removed quickly, and without any tools. This was invented in the 1920's by Tullio Campagnolo, when he suffered a flat while racing over the Croce d'Aune pass in the Italian Alps. His frozen fingers were unable to loosen the wing nuts used to hold his wheels in place.

When quick-release wheels started being supplied on bicycles intended for the general consumer market, ignorant users caused a rash of accidents due to front wheels falling off. The resulting lawsuits led to the addition of "lawyer lips" to most front forks, greatly reducing the convenience of quick release wheels.

It is important to realize that there are good and bad quick-release mechanisms, and the bad ones outnumber the good ones!

See my Article on Quick Release Skewers for details on this.

Recently there have been concerns about the safety of front disc brakes, in conjunction with lightweight quick-release skewers. See James Annan's article on this topic.

Quick-release Brakes

To facilitate wheel changes, most high-performance road bicycles have a quick release mechanism that allows the brakes to be temporarily opened a bit wider than usual, so that the tire can fit through the brake pads.

Some brake quick releases are located in the brake levers, which is the best place for them. This type of quick release allows the brakes to work normally even if the user forgets to reset them after use.

Other quick-releases are located at the caliper or on the cable hanger. These must be manually reset after use, or the brakes may run out of travel. The better caliper-mounted QR's feature a cam which allows a variable setting. This is of use to racers who may knock a wheel out of true, because they can temporarily loosen the QR as much as it takes to get the bent wheel to clear the brake shoes.

Quick-release Seatpost Binders

In the early days of the mountain bike, West coast riders often liked to ride up their mountains with the saddle set at a normal height for efficient pedaling, then drop it down low for the descent. Going down the mountain, they didn't need to pedal, and the lower saddle made it easier to move their weight around for maximum control and shock absorbency.

This feature was carried over when mountain bikes made it into the mass market. Naive bicycle buyers think that a quick-release seatpost is a nifty feature, but it is actually much more trouble than it is worth for most cyclists. In particular, it is very undesirable for urban cyclists, because it has made it necessary to worry about having your saddle and seatpost stolen, a crime that was virtually unknown before the advent of quick-release seatposts.

In the mid 1980's there were also seatposts with quick-release saddle clamps, which allowed the saddle to be moved back and forth over a considerable range. This turned out to be a solution in search of a problem, and was not embraced by the marketplace. Part of the reason for this may be the fact that these seatposts were marketed for mountain-bike use, but were much too short for normally fitted mountain bikes.

Quill

The vertical part of a comventional handlebar stem.
A traditional-style pedal for use with toe clips and straps is sometimes called a "quill" pedal, but I have been unable to discover why.

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