Quick release skewers are rods which are threaded at one end, with a cam assembly on the other. This combines to make a lever operated cam system. The quick release mechanism was invented in 1927 by Tullio Campagnolo, who was an Italian bicycle racer. He was frustrated when he needed to repair a apartment tire during a race, the weather had turned cold, and his hands were numb, so he could not operate the wingnuts which retained the wheel. He had been well-placed prior to the puncture, but lost valuable time, so decided to develop a quick release skewer system which enables simple wheel removal in seconds.
Quick releases tend not to be used on certain types of bicycles, such as utility bicycles (with a single speed or hub gears) or track bicycles, partly because of tradition and partly because there is less need for quick removal of wheels without using tools.Quick releases are sometimes recommended against with the use of disk brakes because of the need for the axle attachment to withstand braking forces.
Over the years quick release mechanisms have been adopted as the primary wheel release devices by the average rider. However, as Sheldon Brown (bicycle mechanic) notes this change has come with some difficulty,Because some bicycle users are competent enough to remove their front wheels but not competent enough to secure them properly when they reinstall them, virtually all new bike purchasers have been deprived of the handy function of quick-release front wheels.This has been done by encumbering fork ends with extra hardware, ridges or lumps that keep the wheel sort-of attached even if it has been installed by someone who doesn't know what he or she is doing. Unfortunately, this means that the quick-release mechanism must be re-adjusted each time it is used, seriously slowing down the operation.
The debate over quick release use as illustrated by Brown, has become a national issue due to several lawsuits brought on by various people including a group of mothers who claim their children were injured due to innocently incorrect use of quick releases.The quick-release levers are usually on the left side of the bike, though some prefer to have them on the right if a disc brake is on the left. Mountain bikers often prefer to point the lever backwards, to reduce the risk of it it catching on undergrowth and being pulled open.