Variation in Bit Construction

Variations of Curb Bit Construction
The shape of individual parts of a curb bit, and the angle of relationship between the various parts, affects the placement and amount of rein pressure that the horse feels.

Curb bits work with leverage action by the use of shanks. The headstall is attached above the mouthpiece on openings on the end of the upper shanks, and the reins are attached below the
mouthpiece on openings or rings at the end of the lower shanks. Curbs with longer lower shanks relative to upper shank length increase pressure by increasing the leverage of pull. Upper shanks are usually 1 inch to 2 inches in length. Lower shank length varies more, with commonly observed differences of 3 inches to 7 inches. However, there are several noted exceptions for upper and lower shank lengths on curb bits.

Curb bits require use of a curb, or chin strap. These straps are made of leather or chain and are attached to the shanks of a curb bit in the area of the headstall ring on the upper shank. Curb straps are positioned to lie under the horse's chin behind the muzzle. Curb, or leverage action is created when reins are attached below the mouthpiece and curb attachment and rein pressure is applied. Curb straps provide the ending point of pressure when rein pressure is applied to curb bits. Most horse show organizations require that chinstraps be at least 1/2 inch in width and lie flat against the jaw. Usual adjustment allows for release of chin pressure when reins are loose. The longer or more loosely attached the chinstrap, the less abrupt and intense the pressure.

The mouthpiece portion that is located between the shank and port is called the bar. The bit’s headstall is adjusted so that the bars are positioned to rest on the bottom palate (the lower gum area between the front and back teeth) of the horse’s mouth. This gum area is also termed the bars of the horse’s mouth. The bar portion of a mouthpiece may extend straight from the shanks to the port, or it may elevate upward and forward. More elevation allows for more area between the mouthpiece and the horse’s tongue. This creates more tongue release, which results in a softer bit.