Horse Side Vet Guide ®

Equine Health Resource

Bit or Bridle Fit Problem

Synonyms: Bit Induced Injury

Poorly fitting tack is an under-recognized cause of equine suffering and poor performance. A bit, mouthpiece or bridle that doesn’t fit, isn’t adjusted properly, or is improperly used may cause pain and result in resistance, poor performance and/or injury.

Many riders do not know why they choose particular bits or bridles. It may be chance, custom, habit, ignorance, poor science or a combination of these that determine their choice. A minority of horsemen know and understand the mechanics of their bit choice. Currently, there is a strong bit-less bridle movement, which is an indication that there is no one right answer to this question.

Size and shape of the bit is important. Bits are roughly divided into direct and indirect pull (shanked) bits. Almost any bit should fit across the mouth so that there is about one-half inch of space on each side, between the lip, and the ring or shank of the bit. If a bit is too narrow, it can pinch the corners of the mouth, causing pain and sores. If it is too wide, it may slide across the mouth and move excessively from side to side.

The bridle should be adjusted so that the bit touches and just wrinkles the corner of the mouth.

The mechanics of shanked bits are complex and poorly understood. Many do not have the desired effect. In my opinion, if you are using a bit, you should know why you are doing it and generally understand how it works. A rider with good hands and horsemanship does not need sophisticated bits or bridles. But some sophisticated riders can make use of bits of sophisticated design.

The severity of a bit depends on many factors, including the diameter of the bit. For shanked bits, the length of the shank relates to the leverage exerted.

A safe choice for someone learning the foundations and for teaching youngsters is a properly fitting round ring snaffle.


  • Are there physical reasons why my horse resists this bit/bridle?
  • Does this tack fit correctly?
  • Is this bit & bridle design appropriate for what I do with my horse?

    Understand the basics of bit mechanics. Good horsemanship alleviates the need for complicated tack.
    Author: Doug Thal DVM Dipl. ABVP


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