Pelham bit

A pelham bit is a type of bit used when riding a horse. It has elements of both a curb bit and a snaffle bit. In this respect a pelham bit functions similar to a double bridle, and like a double bridle it normally has "double" reins: a set of curb reins and a set of snaffle reins. Because it has a bit shank and can exert curb-style pressure on the horse, it is considered a curb bit. Like all curb bits, a pelham bit has a mouthpiece, shanks with both purchase and lever arms, a ring for rein attachment at the bottom of the shank, and a curb chain. But like a snaffle bit, a pelham bit also has a bit ring on either side of the mouthpiece. Like some curb bits, a pelham bit usually has "loose" shanks - hinged at the mouthpiece in the same way that the rings of a snaffle bit are hinged. When two sets of reins are used, the snaffle rein generally is wider, to help distinguish it from the curb. A "cowboy pelham" is a western style of loose-jawed curb bit with additional rings at the mouthpiece allowing a second set of reins to be added.

A pelham works on several parts of a horse's head, depending on which rein is applied. The mouthpiece acts when either the snaffle or curb rein is applied and puts pressure on the bars, tongue, and lips of the horse. The curb chain and design of the mouthpiece can alter the degree of pressure placed on the horse's mouth. The roof of the mouth is affected if the bit mouthpiece of the pelham has a high port or if it is jointed. Pressure on the poll occurs when the curb rein is engaged, and pressure is directly related to the length of the upper shank (purchase arm) in relation to the lower shank (lever arm). All pelhams apply some pressure on the poll. Pressure is applied to the chin groove by the curb chain when the curb rein is used. Direct rein pressure from the snaffle rein may put some pressure on the sides of the horse's mouth, depending on the specific bit design.

A pelham is a leverage bit, meaning that is increases the force but reduces the extent of movement applied by the rider. Unlike a snaffle bit, the curb rein can amplify the rein pressure several times over, depending on the geometry and length of the shank. Shank lengths are 2 inches (5.1 cm) ("Tom Thumb") and longer, although most are less than 4 inches (10 cm).

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