In a double bridle arrangement, the curb or Weymouth serves to assist in achieving maximum flexion from the horse while preserving a light contact. The curb acts on several parts of the horse at once to achieve this result. In the mouth, the curb puts pressure over the tongue and bars, which can be more or less severe depending on how tight the curb chain is kept, how much of a port the mouthpiece has, and how long the shanks are (a too tight or too loose curb chain, a higher port, and longer shanks are all more severe).

The curb uses a leverage action, since it attaches to the cheek and headpieces of the bridle at a point above the mouthpiece, and the reins attach to the end of a shank (essentially a lever) a few inches below the mouthpiece. When the rein is engaged, this lever action puts some pressure on the poll of the horse through the cheek and headpiece, and on the mouth and jaw through essentially squeezing the lower jaw between the mouthpiece and the curb chain running under the jaw.

A tighter curb chain limits the amount of angle that the curb shanks can travel, thus causing less pressure to be put on the poll and jaw. However, this does mean that the action comes into play more immediately upon contacting the rein. The ideal point at which the curb chain should engage is when the cheeks are approximately at a 45 degree angle to the mouth of the horse.

In any case, it should be clear that the curb is a very sharp instrument and should be used only in the hands of those that have a very sensitive touch.

Fixed vs. Slide Cheek

Most curbs today have fixed cheeks, meaning that the shanks are molded to the mouthpiece in one solid piece. The slide cheek, though utilized more in the past, can still be found today, and features cheeks that pass through bores […]

Tom Thumb

A Tom Thumb typically refers to a short shanked curb or pelham bit with swiveling cheeks. It is a mild type of curb, since the shorter cheeks limit the amount of leverage that can be used. Most curbs today come […]

Banbury or Revolver Curb

In the category of specialty curb bits, there is a particular type of arrangement that has been referred to as a Banbury or Revolver Curb. This type of bit has slotted cheeks, which allows the mouthpiece to rotate, and thus […]

Mullen Mouth

Just like the mullen mouth snaffle, a curb with a straight mouthpiece is also referred to as a mullen mouth. While most curbs have some degree of port (an elevated curve in the middle of the mouthpiece), the mullen mouth […]

Angled Port or Conrad

In an angled port or Conrad, the port is angled forward about 60 degrees in relation to the cheeks. The theory behind this according to one manufacturer is that it allows for better palate clearance. This seems somewhat counterintuitive, since […]

S-Cheek

The s-cheek curb has elegantly curved cheek pieces that describe a backwards ā€œSā€ when viewed from the side. This is a classical-looking bit that also evokes an older military style. Functionally, it works basically the same as a straight-shanked curb, […]

Ported Curb

Most curb bits have some degree of port, which is to say an elevated curve in the middle of the mouthpiece. The port makes room for the horse’s tongue to rise up when the bit is engaged, thus putting less […]

Curb Chains and Straps

The function of any curb is dependent on a properly adjusted curb chain or strap. Fitting into the chin groove and hooked to either side of the bit, the curb chain limits the amount of angle that the curb shanks […]