Explaining the action of leverage or curb bits

LEVERAGE or Curb bits have wide variations within the group, from long-shanked western styles to the Weymouth in a double bridle, the Pelham and the misnamed Dutch Gag. Leverage bits employ pressures across the lower jaw and tongue, the poll and, if a curb chain or strap is fitted, it also applies pressure to the curb groove.

The curb chain acts on a nerve that runs under the jaw and, combined with the action of the mouthpiece, encourages relaxation and flexion of the jaw, and retraction of the nose. Any bit with long shanks – Weymouth, Pelham, Dutch Gag, Elevator bits – employ a leverage effect with pressure on the poll and across the lower jaw, with the level of force getting stronger the longer the shanks are.

Anita Marchesani from the Bit Bank Australia explains how a curb or leverage bit works: “A good way to understand how a curb/ leverage bit works is to imagine you need to change a flat tyre. You try to loosen the nuts with your fingers (direct pressure, like a snaffle), but the nuts won’t budge. So you go and grab your tyre iron – the added length of the iron increases the pressure through leverage force, and the nuts loosen. You haven’t gotten any stronger, but the length of the iron increases the pressure applied on the nut.

“This is what happens with leverage bits as well. To try it out for yourself, take a Pelham bit or a Weymouth and pop your foot in between the mouthpiece and the curb chain, as if it was the horse’s lower jaw.  Now take up the reins and see how little you need to move your hands to get a big result on your foot!”

Leverage or curb bits are generally a bit that asks for head lowering and can be useful with horses that tend to travel with the head up or strung out. The Weymouth bit in a double bridle helps refine and define the head carriage and overall collection. A Pelham can be a useful bit for a strong horse going cross-country that tends to stick his head up and not look to the fence.

Contrary to popular belief, the Dutch Gag is not a gag, but really works as a leverage bit, employing sometimes severe pressure and force across the lower jaw, thus creating a head lowering effect. Ideally, a Dutch gag of the three or four-ring variety would be ridden with two reins (one on the snaffle, and one on the leverage rings) to prevent over-bending and give relief to the horse from constant pressure.

This is how a leverage bit works, by giving the rider additional power through the rein aids. It can mean a more subtle, harmonious ride if used by the rider with thought and care, or it can lead to the horse backing off the bit completely, or rolling and tucking the nose under to evade the pressure if not.