While some people automatically reach for a 5″ bit for their horse, assuming it’s the “standard” size, most of the horses I’ve need a wider bit.
In a horse’s mouth the bit sit over the bars of the mouth, the soft tissue area located behind the front teeth. The mouthpiece should be long enough that the side pieces to not rub the corners of the mouth. If the bit is too small it will pinch and/or rub. If it’s too long, it can change the way the mouthpiece sits in the horse’s mouth making it less stable or allowing the horse’s tongue to go over the bit.
You also need to keep in mind the types of mouthpiece and cheek pieces.
- Loose ring bits, where the mouthpiece rotates on the ring, should be fitted with enough room to prevent pinching when the bit rotates; fixed ring bits, such as eggbutt snaffles, D’s and Full Cheeks, can be fitted more closely.
- Single jointed bits shorten in the horse’s mouth when you take up contact, so it’s a good idea to start with a slightly wider bit.
- Double jointed bits can be fitted more closely as the way the bit drapes in the mouth will cause the bit to move away from the rings when you take up contact.
- Mullen mouth (straight, unbroken mouthpieces) won’t change at all with contact so should be fitted so the horse’s lips are just touching the cheekpieces of the bit.
To measure the width of your horse’s mouth, you can buy a bit measuring device like the Bitfit or you can improvise with materials you have around the barn.
Step #1: To measure the width of your horse’s mouth, find a soft, safe material to put in his mouth. you could use a piece of rubber tubing, like a garden hose, or a piece of string. You can also use a wooden dowel but make sure it’s smooth.
Step #2: Put the measuring material into your horse’s mouth so that it rests over the bars, just like you would place a bit.
Step #3: Once it’s in the correct position, mark the edges of the material where it meets the edge of the horse’s lips.
Step #4: Remove the strand from his mouth and use your measuring tape to determine the length between markings in inches.
Measuring the width of a horse’s mouth using the Bitfit tool:
Measuring the width of a horse’s mouth using a piece of wood.