used curb bits—they're a standard piece of tack for any Western rider—but do
you know how and why they function the way they do? Here are the parts and
their purpose, broken down.
Illustration by McKibillo
The curb bit is a leverage bit, which works by amplifying the amount of pressure applied by the rider; 5 pounds of pressure might feel like 10, 15, or 20 pounds to the horse. This allows the rider to rate speed and encourage collection with only minimal hand movement. Unlike snaffle bits, which operate by directly applying pressure on the corners of a horse’s mouth, curb bits affect the lower jaw, tongue, poll, and chin groove. They should only be used on horses that have already been started and respond to neck reining.
The length of a shank determines how much leverage the bit has. The longer the shank, the greater the leverage, so long-shanked curbs should be used with light contact and by more experienced riders and more advanced horses. The angle of the shank determines the immediacy of the rein cue. Straight shanks provide a nearly instant cue when the reins are raised, while swept-back shanks allow for more pre-signaling before the bit is engaged. Swivel shanks—good for horses transitioning from the snaffle to the curb—allow the rider to use both hands, improving communication with the sides of the horse’s mouth.
The port of a curb bit provides tongue relief to the horse, and they come in a variety of shapes to suit various mouth conformations. The higher the port, the greater the tongue relief. However, once a port reaches a certain height (approximately 2 inches), it has the additional function of applying pressure to the roof of the horse’s mouth. This encourages the horse to lower its head and flex at the poll. Cathedral, spade, and correction bits generally feature high ports. Some curb bits come with rollers, which promote salivating. They are also a good mental diversion for fussy or nervous horses and those with busy mouths.
The curb strap is engaged when the reins are lifted, simultaneously applying pressure to the chin groove and pulling the bit down against the bars of the horse’s mouth. A looser curb strap allows for a more gradual cue while a tight curb strap applies greater, more immediate pressure. Curb straps can be made from leather (shown), chain, or synthetic material, and some associations have rules about which materials are allowed at their shows.