Kimberewicks are modified curb bits, and a curb bit is used in a double bridle along with a bradoon. A curb bit is, in general, more severe than a basic snaffle bit, although there are several factors that are involved in determining a bit's severity. Liverpool bits are a type of curb bit commonly used for horses in harness.
The curb bit
Parts of a curb bit
The curb bit consists of a mouthpiece, curb chain, and a shank, with one ring on each side of the purchase arm of the shank, and one ring on the bottom of the lever arm of the shank. Pelham bits add a ring for a snaffle rein, next to the mouthpiece.
Action
A curb bit works on several parts of a horse's head and mouth. The bit mouthpiece acts on the bars, tongue and roof of the mouth. The shanks add leverage and place pressure on the poll via the crownpiece of the bridle, to the chin groove via the curb chain, and, especially with a "loose jaw" shank, may act on the sides of the mouth and jaw.
A decorative fixed shank on a western Salinas-style curb bit
A curb bit is a leverage bit, meaning that it multiplies the pressure applied by the rider. Unlike a snaffle bit, which applies direct rein pressure from the rider's hand to the horse's mouth, the curb can amplify rein pressure several times over, depending on the length of the curb's bit shank. Shank sizes vary from the Tom Thumb (2 inches long) to more than 5 inches. The longer the bit shank, the more powerful its potential effect on the horse. For this reason, overall shank or cheek length, from the top of the cheek ring to the bottom of the rein ring, usually cannot exceed 8+1⁄2 inches for most horse show disciplines.
Bit shanks, such as those on this spade bit, work as a lever
The relation of the upper shank (purchase)—the shank length from the mouthpiece to the cheekpiece rings—and the lower shank or lever arm—the shank length from the mouthpiece to the lowest rein ring, is important in the severity of the bit. The standard curb bit has a 1+1⁄2" purchase and a 4+1⁄2" lower shank, thus producing a 1:3 ratio of purchase to lower shank, a 1:4 ratio of purchase to full shank, thus producing 3lbs of pressure on the chin groove and 4lbs of pressure on the horse's mouth for every 1lb placed on the reins (3 and 4 newtons respectively for every newton).
Regardless of the ratio, the longer the shank, the less force is needed on the reins to provide a given amount of pressure on the mouth. So, if one were to apply 1lb of pressure on the horse's mouth, a 2" shank would need more rein pressure than an 8" shank to provide the same effect.
A long lower shank in relation to the upper shank (or purchase) increases the leverage, and thus the pressure, on the curb groove and the bars of the mouth. A long purchase in relation to the lower shank increases the pressure on the poll and chin, but does not apply as much pressure on the bars of the mouth. A longer purchase will also lift the cannons up and cause significant lip stretch, with an increased danger of dragging the cannons of the bit into the premolars.
A horse has more warning or pre-signal, in a long-shanked bit, allowing it to respond before any significant pressure is applied to its mouth, than it would in a shorter-shanked bit, but ultimately it is the straightness or curve of the shank which translates to the abruptness of response. A straight shank, following the line of leverage, will produce a faster response in the mouth and curb than a shorter curved shank. In this way, a longer shank can allow better communication between horse and rider, without increasing severity. This is also directly dependent on the tightness of the curb chain. Pre-signal is everything that happens before the curbstrap engages, so a properly adjusted curbstrap is paramount in determining the amount of rotation and the timeframe a horse has to prepare for the bit to engage. Too tight and the action is abrupt and severe, too loose and the action is slower, but the bit rotates further, causing it to lift in the mouth and hit the premolars.
Shanks come in a variety of types, which may affect the action of the bit. Some shanks are loose-jawed, meaning they swivel where the mouthpiece attaches to the shank. Others have a loose, rotating ring at the bottom of the shank for rein attachment. Both of these functions allow slight rotation before the bit engages, again providing a "warning" to the horse before the bit engages fully and allowing him to respond to the slightest pressure, thus increasing communication between horse and rider.
The cheek-shank angle also varies, with some straight up and down, others with the shanks curving backward, and some with an S-curve in the shank. The straighter the cheek-shank line is, the less signal is provided to the horse before the bit engages. Those that curve backward provide more of a signal to the horse. Therefore, the type of shank needs to be considered according to the use of the horse. Horses that maintain a more vertical head position, such as dressage horses, generally use a curb bit with straight shanks. Those that have a nose-out head position when working, such as cutting and roping horses, more commonly use a curved shank.
A medium port curb offers considerable tongue relief. The addition of loose-jaw short shanks make this a relatively mild bit.
The curb bit's mouthpiece controls the pressure on the tongue, roof of the mouth, and bars. A mullen mouth places even pressure on the bars and tongue. A port places more pressure on the bars, but provides room for the tongue. A high port may act on the roof of the mouth as it touches. Some Western style curbs, particularly the spade bit, have both a straight bar mouthpiece and a high welded port, thus acting on the bars, tongue and palate. In the wrong hands, such bits can be extremely severe, but on an exquisitely trained animal, they allow the rider to communicate with the horse with a simple touch of the fingertips to the reins.
Curb bits can also be purchased with a variety of jointed mouthpieces that are sometimes mistakenly called "snaffles", some of which (like the twisted wire) can further increase severity. Jointed mouthpieces increase the pressure on the bars due to the nutcracker action of the mouthpiece. In addition, the joint angle is altered by the shank leverage to tip the bit downward and into the tongue. These bits, sometimes called "cowboy snaffles" due to their popularity among western riders, are actually more harsh than a curb with a simple, solid, ported mouthpiece.
The curb chain or strap applies pressure to the curb groove under a horse's chin. When the shank of the bit rotates back (due to rein pressure), the cheek of the bit rotates forward since it is a lever arm. The curb chain is attached to the rings at the end of the cheek. So as the cheek moves forward, it pulls the curb chain, tightening in the curb groove. Once it comes in contact with the curb groove of the horse it acts as a fulcrum, causing the cannons of the bit mouthpiece to push down onto the horse's bars, thus amplifying the bit's pressure on the bars of the horse's mouth.
The action of the bit is therefore also dependent on the tightness of the curb chain. If the bit is used without a curb chain (very uncommon—and dangerous), it loses its leverage action. If used with a loose curb chain, it allows the shanks to rotate more before the curb chain is tight enough to act as a fulcrum and exert pressure. This extra rotation can warn the horse before pressure is exerted on the mouth, so the well-trained horse may respond faster. If used with a very tight curb chain, the bit immediately exerts leverage and increased pressure on the bars as soon as pressure is applied to the reins. Therefore, a tight curb chain is harsher, and provides less finesse in signaling the horse than a looser curb chain would.
Less often seen is the lip strap, a thin strap or light chain that helps keep the curb chain in place and also prevents the horse from grabbing, or "lipping" the bit shanks with its mouth.
Styles
A carriage team's wheeler, in a Liverpool bit set up with minimum leverage. The leaders' two pairs of reins can also be seen being joined into one balanced pair.
Curb bits have tremendous variation, from the relatively simple English Weymouth curb or the simple western medium-port curb to very elaborate designs with complex mouthpieces and shank designs. Some of the more common include:
Weymouth or Weymouth curb: commonly used in a double bridle. It is an English style with a straight shank. The mouthpiece can be one of numerous styles, but usually it is solid, with a low port.[1]
Grazing bit: A western curb with shanks turned back nearly 90 degrees, allegedly to allow the horse to graze while wearing a curb bit. Modern western bits with moderately curved or angled shanks are sometimes called grazing bits, even if the angle is less extreme than the original design.
Spade bit: A historic vaquero design with straight, highly decorated shanks and a mouthpiece that includes a straight bar, a narrow port with a cricket, and a "spoon," a flat, partly rounded plate affixed above the port, supported by braces on either side. Considered a highly technical piece of equipment to be used only on a finished horse.
Liverpool bit: A curb bit with several rein-attachment slots on the curb arms, giving a choice of leverage – the reins may alternatively be attached directly to the bit to use it as a simple snaffle. Used for horses in harness, especially when working in teams, when different horses may require different treatment – their bits can be adjusted so the same tension on the reins of each horse gives a similar result. This allows the reins of the different horses in a team to be joined together, minimising the number of reins the driver has to manage.
Fitting
Curbs are generally placed lower down in a horse's mouth than snaffle bits, touching the corners of the mouth, or creating a single slight wrinkle in the lips. The lower the bit is placed, the more severe it is as the bars of the mouth get thinner and pressure is more concentrated.
The curb chain should be adjusted correctly, lying flat against the chin groove and only coming into action against the jaw when the shank is rotated, but not so loose that the shank exceeds 45 degrees of rotation.
Tack is equipment or accessories equipped on horses and other equines in the course of their use as domesticated animals. This equipment includes such items as saddles, stirrups, bridles, halters, reins, bits, and harnesses. Equipping a horse is often referred to as tacking up, and involves putting the tack equipment on the horse. A room to store such equipment, usually near or in a stable, is a tack room.
A bridle is a piece of equipment used to direct a horse. As defined in the Oxford English Dictionary, the "bridle" includes both the headstall that holds a bit that goes in the mouth of a horse, and the reins that are attached to the bit.
A noseband is the part of a horse's bridle that encircles the nose and jaw of the horse. In English riding, where the noseband is separately attached to its own headstall or crownpiece, held independently of the bit, it is often called a cavesson or caveson noseband. In other styles of riding, a simple noseband is sometimes attached directly to the same headstall as the 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 curb chain, or curb strap, is a piece of horse tack required for proper use on any type of curb bit. It is a flat linked chain or flat strap that runs under the chin groove of the horse, between the bit shank's purchase arms. It has a buckle or hook attachment and English designs have a "fly link" in the middle to hold a lip strap. On English bridles the horse is bridled with the curb chain undone on one side, then connected once on the horse. On western bridles, the curb chain is kept buckled to both sides of the bit.
A snaffle bit is the most common type of bit used while riding horses. It consists of a bit mouthpiece with a ring on each side and acts with direct pressure. A bridle utilizing only a snaffle bit is often called a "snaffle bridle", particularly in the English riding disciplines. A bridle that carries two bits, a curb bit and a snaffle, or "bradoon", is called a double bridle.
A Kimblewick, Kimberwicke or Kimberwick is a type of bit used on a horse, and named after the English town of Kimblewick where it was first made. The bit has bit shanks, D-shaped rings, and a curb chain. Due to its shanks, it is regarded as a type of curb bit. The curb action is minimal to mild, however, because the shanks have short purchase arms and no lever arms. Some variations increase the curb action. A Kimblewick is used with one set of reins.
A double bridle, also called a full bridle or Weymouth bridle, is a bridle that has two bits and four reins. One bit is the bradoon, is a modified snaffle bit that is smaller in diameter and has smaller bit rings than a traditional snaffle, and it is adjusted so that it sits above and behind the other bit, a curb bit. Another term for this combination of curb and snaffle bit is a "bit and bradoon", where the word "bit" in this particular context refers to the curb.
The gag bit is a type of bit for a horse. Because the cheek piece and reins attach to different rings there is leverage action. Severity of leverage action depends on where the reins attach. For example, in a Dutch Gag, the further the rein attachment from the mouthpiece the greater the leverage. The gag bit is related to a Pelham bit and a double bridle but the gag bit has no curb strap.
Reins are items of horse tack, used to direct a horse or other animal used for riding. They are long straps that can be made of leather, nylon, metal, or other materials, and attach to a bridle via either its bit or its noseband.
A hackamore is a type of animal headgear which does not have a bit. Instead, it has a special type of noseband that works on pressure points on the face, nose, and chin. Hackamores are most often seen in western riding and other styles of riding derived from Spanish traditions, and are occasionally seen in some English riding disciplines such as show jumping and the stadium phase of eventing. Various hackamore designs are also popular for endurance riding. While usually used to start young horses, they are often seen on mature horses with dental issues that make bit use painful, and on horses with mouth or tongue injuries that would be aggravated by a bit. Some riders also like to use them in the winter to avoid putting a frozen metal bit into a horse's mouth. In the Mexican Charro tradition, the Jáquima and Bozal substituted for the serrated iron cavesson used in Spain for training horses.
The bit shank is the side piece or cheekpiece of a curb bit, part of the bridle, used when riding on horses. The bit shank allows leverage to be added to the pressure of the rider's hands on the bit. Shanks are usually made of metal, may be straight or curved, and may be decorated in some disciplines. The headstall and curb chain or curb strap of the bridle is attached to the top of the shank, and the reins are attached at the bottom. Shanked curb bits are used in western riding for nearly all adult horses, and are seen in English riding disciplines primarily as part of the double bridle used by advanced dressage riders, and on the hybrid pelham bit that includes a ring for a second rein attached at the bit mouthpiece.
A mechanical hackamore is a piece of horse tack that is a type of bitless headgear for horses where the reins connect to shanks placed between a noseband and a curb chain. Other names include "hackamore bit", "brockamore", "English hackamore", "nose bridle" and "German hackamore". Certain designs have been called "Blair's Pattern" and the "W. S. Bitless Pelham".
Draw reins and running reins are pieces of riding equipment used for training that use the mechanical advantage of a 'single movable pulley' to cause the horse to bring its head down and inward. While a regular rein is the strap that attaches to the bit and is held by the rider, these types of reins slide through the bit ring, adding leverage to the rider's hands and arms, allowing the rider to force the horse's head into a desired position.
The bit ring is the ring on the side of a horse's bit, particularly on a snaffle bit. It is used as a point of attachment for the cheekpieces of the bridle and for the reins. It also has an effect on the action of the bit. Therefore, the design of the ring is something to consider when choosing a bit for a horse, even though the bit mouthpiece generally has a greater effect than the ring.
The mouthpiece is the part of a horse's bit that goes into the mouth of a horse, resting on the bars of the mouth in the sensitive interdental space where there are no teeth. The mouthpiece is possibly the most important determinant in the severity and action of the bit. Some mouthpieces are not allowed in dressage competition.
The bit is an item of a horse's tack. It usually refers to the assembly of components that contacts and controls the horse's mouth, and includes the shanks, rings, cheekpads and mullen, all described here below, but it also sometimes simply refers to the mullen, the piece that fits inside the horse's mouth. The mullen extends across the horse's mouth and rests on the bars, the region between the incisors and molars where there are no teeth. The bit is located on the horse's head by the headstall, and which has itself several components to allow the most comfortable adjustment of bit location and control.
A bitless bridle is a general term describing a wide range of headgear for horses or other animals that controls the animal without using a bit. Direction control may also be via a noseband or cavesson, if one is used. The term hackamore is the most historically accurate word for most common forms of bitless headgear. However, some modern bitless designs of horse headgear lack the heavy noseband of a true hackamore and instead use straps that tighten around a horse's head to apply pressure in various ways. These are often specifically patented and marketed as "bitless bridles", usually referencing a particular type of headgear known as the cross-under, though other designs are sometimes also given similar names.
A lip strap is a piece of horse tack made of rolled leather or occasionally thin chain, used sometimes on some types of English-style curb and pelham bits. The lip strap runs between the bit shanks and passes through a special center ring on a curb chain sometimes called the "fly link". The lip strap attaches to rings at midpoint of the shanks and buckles on the near side.
The spade bit is a historic vaquero design for a type of curb bit with straight, highly decorated shanks and a mouthpiece that includes a straight bar, a narrow port with a cricket, and a "spoon," a flat, partly rounded plate affixed above the port, supported by braces on either side. Considered a highly technical piece of equipment to be used only on a finished horse, the spade bit is a refined tool that experts compare to driving a sports car in its ability to convey precise commands to the horse. Not all horses have the conformation or temperament to become a finished spade bit horse, a process that takes a number of years and is seldom complete until a horse has at least five years of training under saddle.
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