Debunking Bit Fitting Myths - The Thicker The Better???

Tammy Levasseur

Posted on February 26 2023

On The Bit Lorinery Solutions - Equine Bit Fitting
In our travels as Certified Bit Fitters, we hear a lot of "theories" on bit fitting that are not factually or scientifically based.   In this series, I will be debunking some common bit-fitting myths, starting with "Fatter bits are more gentle."

Most of us have been taught thicker bits are more gentle in the horse’s mouth than thinner bits.

And most of us have never really challenged that logic. The general notion has typically been that a thicker mouthpiece puts less concentrated pressure on the bars of the mouth or tongue than a narrower bit and is therefore more gentle and kind. It is a myth that putting a fatter bit in your horse’s mouth is more gentle.

It is not consistently true that a thicker bit is more kind; It depends greatly on the individual horse’s oral anatomy. While a thicker bit may apply a different pressure where it comes in contact with the structures in the mouth, it takes up more room in the oral cavity. As bit fitters, we measure several different aspects of the oral and cranial anatomy. One of the metrics of interest is the “Interdental Space Height” (the measurement between the upper bar of the mouth and the lower bar). This measurement gives us an idea what thickness of bit a horse can most comfortably accommodate.

For example, if a horse only has 28mm of Interdental Space Height and we choose a bit that is 20mm, the horse will struggle to accommodate the size of the bit. The horse will respond by pulling its tongue back in the oral cavity, causing tension in the throat latch and poll, creating resistance, and resulting in an unhappy horse. The correct approach is to find out what is going on in the horse’s oral cavity and choose a bit that is better suited, before contact issues develop.

If you have any questions about this subjecy or would like help with your bit and bridle fit, please feel free to email

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