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For many years, the toe clip was the primary pedal system on racing bicycles. The toe clip was a metal or plastic cage that the cyclist slipped his foot into, enabling him to pull up on the pedals during his pedal stroke in addition to pushing down on them. While this elevated power output, toe clips were cumbersome and difficult to get in and out of. Therefore, clipless pedals were born. Clipless pedals also allow a cyclist to pull up on the pedals, but there is no cage for the cyclist’s foot to slip into. Instead, the cyclist wears a special shoe with a cleat attached to the bottom; the cleat then snaps into specially designed pedals, much like a ski binding but far more compact.
Clipless pedals are less a pedal and more a pedal system. They work in conjunction with the cyclist’s shoe, which features a very stiff sole made of plastic, carbon, or other hard substances. A specially designed cleat then attaches to the bottom of the shoe and acts as the interface between the shoe and the pedal. Clipless pedals themselves range in shape and size depending on a particular brand’s design, but most are made to shed mud effectively. Early versions of clipless pedals would get clogged and fail to function properly as mud was jammed into the spring mechanisms during riding.
On most mountain bike clipless pedals, the cleat must slide, toe-first, under a bar on the pedal. The cyclist then pushes his heel down, and a spring-loaded rear bar on the pedal clips into place on the rear of the cleat. The cyclist is then essentially locked into the bicycle. In order to release his foot from the clipless pedal, the cyclist must twist his heel outward away from the bicycle, thereby releasing the cleat from the spring-loaded bar.
Some road bicycling clipless pedals work slightly differently. For example, Speedplay’s road pedal systems work in the opposite manner as the mountain bike pedals described above. The bars usually attached to the pedal are instead attached to a cleat on the rider’s shoe – which is much bulkier than most cleats – and the pedal itself acts in the same way as the mountain bike cleat mentioned above. When the rider presses his foot against the pedal, the springs that move to connect the interface are on the shoe rather than the pedal. But releasing from the clipless pedals works in the same way: the rider kicks his heel outward from the bike.
Even though the cyclist’s shoes are locked into the clipless pedal, the foot is allowed to move side to side. This is called float and many pedals now offer a float adjustment that lets the rider decide how much movement his foot is allowed. But be careful: limiting your float too much can be damaging to your knees, and not limiting it enough could encourage accidental releases from the pedal.