The Bridle Wars Part 3: Understanding Mouthpieces

The other important part to understanding bit action is understanding how the mouthpiece of a bit will function. There is one relatively reliable rule: with the possible exception of horses with low palates, the thinner the mouthpiece the more severe the bit's action. This is because the pressure will be concentrated over a smaller area.

Please note that this post is restricted to solid smooth metal bits with no twists or coatings. Twists or chains make for a severe bit, one that I feel is more likely to be abusive than to prove helpful. Rubber bits and rubber coatings have the opposite effect and make a bit softer and more forgiving. I am not a fan of these, (see Part 1: Not A Happy Mouth) though they do potentially have their uses.

There are many different mouthpieces even given our restrictions, but as a general rule we'll break it into four types: solid (aka mullen mouthed), ported, single jointed, and double jointed.

A solid mouthed bit will apply the most pressure to the horse's tongue. As a general rule a solid mouthed bit is a mild bit. It is a good option for horses that have a low pallet as there is no way this bit can poke the horse in the roof of the mouth, an action that can cause the horse to throw his head in the air. There are however horses that dislike tongue pressure and will fight a bits of this style.

A ported mouthpiece is less common on snaffle bits, and more common on leverage bits. A ported mouthpiece will apply less pressure to the horse's tongue and more to the bars of the mouth. This can be helpful for a horse that resents tongue pressure. This also makes the bit more severe because the pressure is being concentrated in a smaller area. The higher the port the more pressure is transfered, and the more severe the bit. A bit with a very high port can also create pressure to the palate (roof of the mouth) as the bit rotates. As mentioned above, this may not be desirable. There is an additional issue with the curb chain leverage action of many ported bits that rather than manifesting palate pressure as head tossing, the horse will learn to break unnaturally at the poll to minimize pressure from both the port and the curb chain. This can result in a horse that carries himself behind the bit, or false carriage in which the horse's head set gives the illusion that the horse is on the bit and carrying himself, when in reality his body may be all over the place. Prolonged work in such a frame can create poor muscle development, and undesirable balance.

A single jointed mouthpiece relieves some of the tongue pressure of a solid mouth, and can apply more pressure to the bars of the mouth. It is generally a mild bit and is widely available in all snaffle varieties. The one caveat with this style of bit is that it can create a severe pressure point on the palate. In horses with a low palate, this may result in head tossing.

A double jointed mouthpiece is generally considered the mildest bit as it most evenly distributes the pressure of the bit across the horse's jaw. It also minimizes the likelihood of pressure points on the palate. However, this type of mouthpiece also adds an additional variable. The center link is highly variable. As a general rule, the larger and smoother the center link, the milder the bit. The sharper or smaller the middle link, the more severe the bit. For example, a bit with a big round oval style center (as pictured at left) is likely to be very mild, a french link with a small center link less so, and a dr. bristol with a center plate set on edge (so that in use the narrow edge of the center link puts severe pressure on the tongue) is much more severe. So think carefully about how the center link will function before you make any judgments about the way the bit will function.