A leather, plastic or metal fitting attached to the bottom of a cycling shoe to provide positive engagement with the pedal.
Classic cleats for use with toe-clip pedals had a simple slot that fitted over the rear edge of the pedal. This provided a consistent position of the foot on the pedal, both in terms of centering the ball of the foot over the pedal spindle, and maintaining the desired foot angle on the pedal.
Up until the late '70's, cleats were leather or aluminum, and were nailed onto the bottom of the shoe with many tiny nails. The usual procedure was to have the cyclist ride for a while without the cleats, until the pedal would make a mark on the sole of the shoe. This mark would then be used as a guide to locate where the cleat should be nailed on.
In the '70's, adjustable plastic cleats were introduced, and immediately rendered the nail-on system obsolete...unfortunately, they also precipitated a rash of knee injuries, because riders would adjust them by pure guesswork, and this often caused un-natural stresses on their knees. The invention of the Fit-Kit R.A.D. made it possible to adjust this type of cleat even more accurately than the old sole-impression system.
Cleats for clipless pedals are made of metal or plastic, and lock into the pedal mechanism. They are adjusted in the same manner as the adjustable cleats of the '70's. Before the invention of clipless pedals, classic cleats were the only way to provide positive, accurate shoe/pedal attachment. They were rather dangerous, however. If the straps were overtightened, it could become impossible to get your foot out in an emergency, and many embarrassing falls have resulted from this. They also were slippery and hazardous to walk on.
Modern clipless pedals have solved these problems, and, in my opinion, nobody should still be using classic cleats. Now that there is an alternative, they are just not worth the risk.
This is the normal type of tire, with a separate inner tube. The tire consists of two hoops called "beads", made of steel or Kevlar cable, which are held together by cloth, usually nylon. The whole assembly is dipped in rubber, with thicker rubber applied in the tread area.
The clincher tire's separate inner tube is basically a rubber balloon. This fits inside the tire, and the tire is mounted on the rim by lifting the beads over the edge of the rim. The middle of the rim makes a sort of valley (the "well"), and while the tire is being installed, most of the bead can fit into this valley. This gives enough slack to allow the bead to be pushed or pulled over the edge of the rim, even though the outside diameter of the rim is larger than the inside diameter of the bead.
Strictly speaking, the term "clincher" is slightly incorrect, as it applied to an obsolete style of tire which had ribs in the edges of the tire which fitted into grooves on the rim, where the tire was folded under the tube. The air pressure in the tube pressed the rib into the groove, and "clinched" the tire in place. People who are fussy about this prefer the term "wired-on."
Other types of tires include airless tires, single-tubes (both obsolete) and tubulars.