Thickness

Different thickness of mouthpieces.

The thickness of the mouth bar(s) is important to the horse. In general, you can say that a thicker bit is milder while a thinner bit is sharper. The thicker bit has a larger contact surface than a thinner bit and therefore spreads the pressure better. But there are other problems when it comes to bit thickness. A thicker bit takes up more space in the mouth, puts more passive pressure on the tongue and the palate and opens the lips more. It can passively be more uncomfortable.

Then, a thicker bit can also be "too mild" if there''''s ever such a thing as too much comfort. This can lead to the horse not "respecting" the bit and that he will easily take the opportunity to lean on it or go against it. That can in turn cause all the heavy handedness that the rider needs to use, to end up in the temple joint of the jaw to the skull. This might not show up in the current work session, but can slowly turn into inflamation and render the horse unable to relax the jaw and poll, before the exercise induced endorfins have generated some painkiller function, after 20 minutes or so. So the need for a long warm-up can be a sign of problems in many ways.