Bit mouthpiece
Commonly used metals include stainless steel and nickel alloys, which generally do not rust and have a neutral effect on salivation; sweet iron, aurigan and copper, which generally tend to encourage salivation; and aluminum, which is considered drying and is discouraged as a mouthpiece metal.
In the mullen mouth, the bar has a slight bow to it, curving gently to allow some room for the tongue.
Variants: A variant that is somewhat between the mullen and a low port, seen primarily in western riding is called a "sweetwater" bit and is a very wide, low port slightly more arched than a mullen that offers full tongue relief, puts pressure only on the bars, and is primarily used as a curb mouthpiece.
The port is different from the mullen mouth in that the curved portion does not extend the width of the mouthpiece, but is only an inch or two in the center of the bar.
Action: Ported bits act on the lips, tongue, and roof of the mouth, and may apply extra pressure to the bars.
Larger ports press on the hard palate (roof of the mouth) when the reins are pulled, act as a fulcrum, and transfer that pressure onto the bars.
Recent research has shown that the port must be 2-2.5" (5–6 cm) or more in height before it touches the hard palate.
Due to the V-shape of the bit when the mouthpiece is contracted, it causes a "nutcracker" action, which has a pinching effect on the bars.
A single-jointed bit with a curved mouthpiece has a more "U" shape which tends to decrease the pressure on the roof of the mouth.
Adding a solid "slobber bar" at the end of the shanks may reduce, but does not eliminate, this problem.
Double-jointed bits reduce the nutcracker effect because they conform better to the horse's U-shaped mouth, instead of the "V" created by a single joint.
Many of the double-jointed bits (especially the French link and Dr. Bristol) are occasionally "added to" by twisting the cannons of the mouthpiece.
A rounded link does not have this action Action: One of the mildest mouthpieces, because the two joints reduce the nutcracker effect found in single-jointed bits, and encourage relaxation—applies pressure to the lips, tongue, and bars of the mouth Materials: Usually stainless steel, also copper (either just the link or the whole bit) Use: Commonly seen on snaffles, rare in gags, pelhams, or curbs.
[1] Action: The double joint reduces the nutcracker effect found in single-jointed snaffles.
As a result, the thin edge of the center link can press into the tongue, creating a very small bearing surface.
It contains a double jointed mouthpiece similar to the French link, with the center section a flat plate.
Bristol insisted that this bit was intended to be comfortable for the horse because the central plate would lie flat onto the tongue thus lowering the pressure.
Academic research has clarified these claims, showing that harsh action occurs when the bit is placed into the mouth such that the feature angle, as defined from a left hand side view, is +45 °.
Type of Bits: snaffle, pelham, gag, curb What it is: The mouthpiece is made of 5-9 joints and is very flexible.
Usually, it is the less-skilled riders who find the need to use harsher bits, because they can't control their horses in anything else.
Nonetheless, in some cases, skilled riders can use such bits to their advantage and improve the horse's training.
Types of Bits: Snaffle, pelham, gag What it is: A mouthpiece (usually single-jointed) with a slight twist in the cannons.
Action: The twist causes edges that result as pressure points in the horse's mouth.
Note: due to the extreme severity, most equestrian organizations do not permit this bit in competition.
Types of bits: snaffle, pelham, gag What it is: A mouthpiece (usually single jointed, but not always) that is hollow in the middle, making it very light.
Action: The thick, hollow mouthpiece spreads out pressure, thought to make it less severe.
The edges of the square mouthpiece create pressure points, making the bit severe.
However, up to a point, some horses perform better with a thinner mouthpiece to a thicker one because there is less metal in their mouth and therefore more room for the tongue.
Thinner mouthpieces are also preferable when using a double bridle, as the horse has even less room for its tongue with two bits in his mouth.
Some wire bits may come in a thickness as low as 1/16 inch, making them extremely severe to the point where it is easy for any rider to cut and ruin the horse's mouth, especially the lips.
