Bit Structure & Function
The bit can be an intimidating piece of equipment to understand. However, if you break down the five structure points of a bit and examine how they affect the four pressure points of a horse’s mouth, bit function becomes something easier to comprehend.
A bit applies pressure to a horse’s palate, tongue, bars and curb. A bit’s design affects how it applies pressure to these four points. When a horseman understands the individual physical characteristics of a horse and the goal of riding, the better that rider can communicate though the bit to meet his needs. The more comfortable the horse is with the rider’s communication, the better the horse and rider will get along.
By applying pressure to one or more of these four pressure points, the horse will react in certain ways. The challenge: the way in which a signal is applied will be unique to each rider, and the reaction to that signal will be unique to each horse. This is why there has never been a menu or checklist created for bitting a horse. However, if you understand those four pressure points, and how you affect these points by changing the structure of the bit, you can come as close a possible to creating your own menu. And it will be your menu, because each of us is unique, including the way in which each of us handles a horse.
A Bit’s 5 Structure Points
Starting at the top, the distance from the bit’s top ring to the butt of the mouthpiece is referred to as the purchase. This distance affects the placement of the curb strap on the horse’s chin. As the purchase length is increased, multiple things happen. First, as the curb moves up the horses jaw, the jaw becomes less sensitive and the ability to control the face (vertical) position of the horse’s head increases. Second, as the distance increases, the speed at which the bit produces a signal (reaction time) decreases. This gives the rider the ability to move his hand more without creating signals to the horse. This can be positive or negative depending on the task at hand.
The next point to discuss is the shank length, which is the distance from the butt of the mouthpiece to the bottom of the shank. This measurement is taken along an imaginary vertical line that carries straight down from the center at the top of the bridle ring through the butt of the mouthpiece; if the shank swoops back, the angle is not measured, simply the vertical distance. Shank length affects a rider’s leverage. As the distance increases in relation to the purchase length, the leverage and speed of the bit is increased. A bit ratio of 2:1, for example, means the shank length is twice as long as the purchase. Most spade bits are around this ratio because of the speed of the bit.; it creates a maximum amount of signal with a minimum amount of hand movement, which is the purpose of the spade.
Shank design and point of pull are the next two structure points. Shank design is the path the shank takes to get from the butt of the mouthpiece to the bottom ring. Point of pull is defined as the distance from the vertical center line to the back of the bottom ring, where the reins are attached. If the shank travels straight to the point of pull with minimal amounts of material, less weight is created in the bit, which affects the signal of the bit. As weight is added to the bit, it becomes easier for the horse to feel the movement in his mouth.
Shank design can also affect the leverage of the bit by changing the point of pull. If a shank’s design puts the point of pull straight down from the mouthpiece on the vertical line, leverage is at a maximum. An example of this is the Las Cruces shank. The Santa Barbara is an example of how a bit can maximize leverage and signal. A lot of material is needed to create the design, which adds more weight and increases the signal.
The next and final point to discuss is the placement, angle and height of the mouthpiece. As the mouthpiece is moved further in front of the vertical line, the bit’s speed is slowed. Height can be added to the port of the mouthpiece to affect palate pressure. A spade, for example, applies palate pressure where a straight bar with no post does not.
The angle of the mouthpiece affects two things:
First, a mouthpiece angled forward takes pressure off the tongue — pressure applied by the port as it sits in a neutral state with no rein pressure — and applies it closer to the palate. If the mouthpiece is capable of applying palate pressure, the closer the mouthpiece is to the palate and the quicker the palate pressure will be applied as the reins are pulled.
Second, the mouthpiece angle affects the balance of the bit. Again, with the vertical line in mind, as the mouthpiece angle is moved behind this line, the balance of the bit becomes flatter — the bit becomes overbalanced. As the mouthpiece is kept vertical and the shank design has little to no weight behind the vertical line, the shank is underbalanced, hanging vertically. This produces a bit that continues to apply pressure if the horse doesn’t pack his head in a vertical position.
One last element to consider is the difference between a loose-jawed bit and a solid-jawed bit. This is how the shanks attach to the mouthpiece. A loose-jawed bit has shanks that swivel independently of the mouthpiece. This accomplishes several things:
First, signal is increased because there are more moving parts to cue the horse that a command is being asked as the rider pulls on the reins. The shanks move, signaling to the horse through lateral movements without necessarily engaging the mouthpiece.
A loose-jawed bit also makes it easier for the horse to differentiate between signals given from one side versus the other. Since the shanks move independently of one another, a rider can cue using single rein pulls to help a horse with lateral signals and movement. This can be a great advantage in young horses that are not yet neck-reining.
A solid-jawed bit moves in its entirety as one or both reins are pulled, requiring the horse to know what the rider is asking based on other signals being given simultaneously. However, with the bit being solid, there isn’t much movement, which might keep your horse quieter in the mouth, given that there’s little signal being inadvertently produced by the horse’s own physical action.
Equipped with knowledge of the four pressure points, a bit’s structure, and how these elements work together, you can now take your favorite bit and break down how it affects your horse and why the horse gets along with that bit (or why he might not).
The Santa Barbara shank for example, offers a straight shank, more leverage, with weight behind the vertical line, adding overbalance, which helps the bit rest in a more comfortable position for the horse to carry during a day’s work. Each Santa Barbara is unique, though, so the rider must check the balance and leverage of the bit. A 2:1 ratio, for example, gives a rider leverage and signal speed.
The amount of weight behind the shank’s vertical line, and the angle of the mouthpiece, will determine your bit’s balance. Comparing the bit’s balance to the natural carriage angle of your horse’s head could determine if you two are on speaking terms at the end of a long day.
This analysis can be done with each shank design and each mouthpiece. The better you understand yourself, your horse, and how a bit reacts, the better you will be able to accomplish your riding goals.