Bicycle pedal

Animation of a bicycle pedal

A bicycle pedal is the part of a bicycle that the rider pushes with his or her foot to propel the bicycle. It provides the connection between the cyclist's foot or shoe and the crank allowing the leg to turn the bottom bracket axle. Pedals usually consist of a spindle that threads into the end of the crank and a body, on which the foot rests or is attached, that is free to rotate on bearings with respect to the spindle.

The Velocipede, a predecessor to the bicycle, lacked pedals but allowed the crank to be operated by means of a treadle. Pedals were initially attached to cranks connecting directly to the driven (usually front) wheel. The safety bicycle as it is known today came into being when the pedals were attached to a crank driving a sprocket that transmitted power to the driven wheel by means of a roller chain.

Flat and platform

File:Platform.JPG

Wellgo BMX Pedal

Traditionally, platform pedals were pedals with a relatively large flat area for the foot to rest on, in contrast to the quill pedal which had very little surface area.

One form of the platform pedal had a large flat top area and flat bottom for use with toe clips and toe straps, and were designed for greater comfort when using shoes with less than rigid soles. They typically had a smaller cutaway underside giving greater cornering clearance, which was often needed on the track. They were often marketed as being more aerodynamic than conventional quill pedals.

Attaching the shoes to the pedals can increase power on the downstroke and harness additional power on the upstroke. This can be done with toe clips and straps, or with shoes having a cleat, which easily attaches and detaches to a compatibly designed (clipless) pedal. Both methods are common on road bikes, but neither on utility bikes.

In mountain biking and BMX, platform pedals typically refer to any flat pedal without a cage. MTB and BMX riders prefer platforms to cage pedals because they offer more grip using short metal studs, are rounder and do less damage to a rider's shins and ankles during an accident. Cage pedals often scrape skin and flesh off the shin if the rider stops short and loses footing of the pedal.

Platform pedals are available in a wide variety of types and prices, ranging from disposable plastic units used for test rides on new bicycles to high-end downhill models. Budget models may be made of steel or aluminium and incorporate reflectors for safer riding on streets at night. Less expensive platform pedals are generally considered disposable and cannot be rebuilt when worn out.

More expensive platform pedals for the mountain bike market are available with replaceable metal traction pins and cartridge bearings. In recent years lightweight pedals intended for Freeride and downhill cycling have been made from exotic metals such as magnesium.

Toe clips typically are not installed on this type of pedal because they are considered unsafe by some MTB and BMX riders. However, fixed gear riders have started using fabric straps instead.

Quill

Mikashima Track Pedal

Very early pedals were simply platforms (with a rotating axis) on which the cyclist could press downward with the foot. Then cages called toe clips were added to help keep the foot in place.

Cages now refers to pedals that can accommodate toe clips and not necessarily the clips themselves, and are more specifically called quill pedals. The actual cage is the outer part of a conventional pedal, the part that comes in contact with the rider's shoe and has holes where toe clips can be secured by screws. Toe straps used with clips further secure the foot to the pedal and to allow the cyclist to apply power on the upstroke by pulling against the pedal. Traditionally toe straps could be used with toe clips in conjunction with cycling shoes fitted with a slotted shoeplate. The clip is generally made of metal or high impact plastic. The strap is generally made of leather or nylon.

The main difference between track, road, and touring quill pedals is width. Track pedals are narrow and the front and back plates of the cage are separate, road being a little wider with a one piece cage in a shape of a sideways "U", and touring being the widest to allow for comfort when used with wider, non-racing shoes during longer rides.

Bicycle pedal (left), quill road type, with toe clip and toe strap. 1970s.

While quill pedals can be used for mountain biking, the use of clips here is dangerous as they do not grip well. Cage pedals built for mountain biking are typically serrated so that even when muddied, the pedals can be gripped well by any flat shoe.

Cycling shoe with a slotted shoeplate attached to its sole

Although quill pedals can be used with smoothed-soled cycling shoes or ordinary shoes, they were designed to be used with cycling shoes which had a slotted shoeplate attached to its sole. The slot in the shoeplate fits into the rear plate of the pedal, and together with the toe strap and to a lesser extent the toeclip, the shoe is held firmly to the pedal. The disadvantage with this system is that to remove the shoe from the pedal a rider had to reach down and loosen the toestrap by hand—or, more commonly with casual riders, leave the toe strap loose and thus give up some efficiency. This type of pedal and shoe were used by all racing cyclists until the mid to late 1980s.

Generally pedals that could be used with toe clips had a "pick up" tab on the rear of the pedal. The weight of the toe clip and strap would make the pedal hang upside down, and the rider would tap the tab with their shoe to flip the pedal over so the shoe could be inserted into the pedal.

Clipless pedals

SPD Dual Choice with shoe

Road LOOK pedals

Clipless pedals (also clip-in or step-in) require a special cycling shoe with a cleat fitted to the sole, which locks into a mechanism in the pedal, holding the shoe firmly to the pedal. Most of today's clipless pedals lock to the cleats when stepped together firmly, and unlock with when the foot is twisted outward. Clipless refers to the lack of an external toe clip (cage), but not to be confused with platform pedals without toe clips.

The clipless pedal was invented by Charles Hanson in 1895. It allowed the rider to twist the shoe to lock and unlock, and had rotational float (the freedom to rotate the shoe slightly to prevent foot strain).

The M71 was a clipless pedal designed by Cino Cinelli and produced by his company in 1971. It used a plastic shoe cleat which slid into grooves in the pedal and locked in place with a small lever located on the back side of the pedal body. To release the shoe a rider had to reach down and operate the lever, similar to the way a racing cyclist had to reach down and loosen the toestrap. The lever was placed on the outside edge of the pedal so that in the event of a fall the lever hitting the ground would release the foot. The pedal was designed for racing, in particular track racing, Because of the need to reach them to unclip they have been referred to as "death cleats".

In 1984, the French company LOOK applied downhill snow skiing binding or cleat technology to pedals producing the first widely used clipless pedals. Initially used by triathletes in order to facilitate faster "transitions", Bernard Hinault's victory in Tour de France in 1985 then helped secure the acceptance of quick-release clipless pedal systems by cyclists. Those pedals, and compatible models by other manufacturers, remain in widespread use today. The cleat is engaged by simply pushing down and forward on the pedal, or, with some designs, by twisting the cleat in sideways. Then, instead of loosening a toestrap or pulling a lever, the cyclist releases a foot from the pedal by twisting the heel outward. First time clipless users may not be proficient in unclipping quickly when coming to a stop, sometimes resulting in a low speed fall.

The next major development in clipless pedals was Shimano's SPD (Shimano Pedaling Dynamics) pedal system. Whereas Look cleats are large and protrude from the sole of the shoe, SPD cleats are small and could be fitted in a recess in the sole, making it possible for walking (although comfort will vary, as the soles of different cycling shoes vary in their rigidity depending on design).

Cycling shoes have rigid soles to maximize power transfer and efficiency. They may be specific to road or mountain biking, or usable for both. Shoes designed for mountain biking typically have recessed cleats that do not protrude beyond the sole of the shoe, and have treads for walking on trails, as walking or carrying the bike is often required. Road cycling shoes are typically lighter than their mountain bike counterparts, and feature a protruding cleat and less weather proofing. The protruding cleat makes these shoes impractical for walking, as doing so can damage the cleat.

Mountain bike cleats can generally be mounted without difficulty to road shoes although sometimes an adapter is required. Such attachment is not usually possible for road pedals, as the cleats are normally too large to be mounted on mountain shoes. The smaller mountain bike cleats are attached to the sole of the shoe by two bolts; larger road-specific cleats are attached by three.

Various other manufacturers have produced their own designs of clipless pedal systems over the years, most notably Crank Brothers, BeBop, Coombe, LOOK, Shimano, Speedplay, and Time.

Magnet pedals

Davtus magnet pedal

Magnetic pedals were introduced as early as 1897, and the Exus Mag Flux Road was available in 1996. More recently, Norbert Sadler and Wolfgang Duerr filed for a patent in 2005. Their pedal uses neodymium iron boron (NdFeB) magnets. The magnetic pedal system allows for a free choice of foot position, which can also be changed while riding and therefore rests the joints and obviates knee problems. The magnetic pedal system allows for immediate release in all directions. A slight movement of the knee outward or tilting the shoe sole off the pedal results in an easy release. In critical situations a fitful pull will also result in the immediate release. Falls will cause an automatic release from the pedal as the magnet strength is limited by nature.

Attachment

The pedal spindle is threaded to match a threaded hole at the outboard end of the cranks. Adult or multi-piece cranks have a 9/16 inch hole with 20 TPI (a diameter/pitch combination fairly unique to this application). One-piece or kids cranks use a 1/2 inch hole. Obsolete French pedal spindles use M14 x 1.25 (14 mm metric with 1.25 mm pitch) threads, and thread loosely into a 9/16 pedal hole. The threading size is often stamped into the crank, near the pedal hole.

The right-side (usually the drive-side) pedal spindle is right-hand threaded, and the left-side (usually the non-drive-side) pedal spindle is left-hand (reverse) threaded to help prevent it from becoming loose by an effect called precession.

Although the left pedal turns clockwise on its bearing relative to the crank (and so would seem to tighten a right-hand thread), the force from the rider's foot presses the spindle against the crank thread at a point which rolls around clockwise with respect to the crank, thus slowly pulling the outside of the pedal spindle anticlockwise (counterclockwise) because of friction and thus would loosen a right-hand thread.

For a short time in the early 1980s, Shimano made pedals and matching cranks that had a 1 inch by 24 TPI interface. This was to allow a larger single bearing, as these pedals were designed to work with just one bearing on the crank side rather than the conventional design of one smaller bearing on each side.

Manufacturers of pedals

Notable manufacturers include:

• Campagnolo
• LOOK
• Shimano
• Speedplay
• Time

See also

• Crankset
• Cycling shoe

External links

• How to remove and install bicycle pedals (video)