Types of Curb Bits

There are many types of curb bits for dressage, with different lengths, shapes and parts. They all have a solid mouthbar without joint, and for competition the length of the shanks is regulated in the rules. I''''ll try to describe some of the curbs for dressage, why they are designed in the way they are, and their different effects.

Length of Shanks

The biggest differences in effect comes from the length of the shanks and the form of the mouth piece. Most people say that the longer the shanks, the sharper the bit. I would have to disagree. I would say that the longer the shanks the stronger the bit, and the shorter the shanks the sharper the bit. Now, this sounds like semantics, but it is really not.
Imagine you had 2 feet long lower shanks. To make them turn the bit around the axis (mouth piece) let''''s say 22,5 degrees one would have to shorten the reins maybe 9 inches! If the lower shank is instead 4 inches, one would have to shorten the reins 1 inch to have the same effect on the angle of the shank. So moving the hands around on the former reins would not have such a direct effect on the bit in the mouth as the latter. Thus one can say that the shorter shank is "sharp" in that small movements of the hand give direct effect. But the long shanks give much more force once they have been hauled in 9 inches. It would be more than possible to break the jaw on the pore animal, much like a long spit used for unearthening big boulders of rock. So longer shanks are stronger in the actual force they can deliver. But you also have to take into consideration the length of the upper shank. A nonexistent upper shank will render the bit virtually effecless. The chin chain will need to be pulled forwards by something, for the mouth piece to have an effect on the tongue and bars. If there for an example were no chin chain, the upper shank would mover forward until horizontal (which has the lower shank pointing horizontally towards the hand and the lever effect can go no further) the only pressure on the bar is the same pressure as with which the rider pulls - like a snaffle. Only that the upper shank would pull the side piece forward and down. And since the side piece doesn''''t yield, the mouth piece will be pulled up. A really bizarre and useless effect on the dressage horse.

So, a really short upper shank lessens the effect of the lower shank. The ideal proportions between the two seem to be that the lower shank be twice as long as the upper. Or thereabout.

Shape of the Mouth Piece

The effect of the shanks is always dependent on the rein aids. No aids - no effect. But the shape of the mouth piece has a direct effect on the horse in that is lies against the tongue and bars, and more or less in contact with the palate. So only lying there, the horse feels it and its shape with his sensitive mouth. Some horses seem to think it OK to have something lying across their tongue, but strongly dislike any contact with the bars, and some are sensitive to tongue pressure but find bar pressure OK. Some like a thick mouthpiece that is smooth in contact but bulky in mass, and some like thin mouthpieces, and tolerate their inherent sharpness. But those are not the only differences there is. Some, like my favourite curb bit, that seems to be preferred by most horses I have met, has a wide, shallow bend to the mouth piece so that it arches around the contour of the tongue. This is not unusual, but what is unusual with this bit is that it has been adjusted to a tongue that is flat and wide, and not like most ports - fairly high but narrow.

Those ports, popular in the 80''''s and 90''''s, that are high and narrow hardly fit the tongue into it, but stand up above the tongue, and poke into or towards the palate. This does not put even pressure on the tongue, does not lower the rest of the mouth piece to come closer to the bars on the sides to the tongue, and makes the whole bit take up unnecessary space in the mouth. And just like any space in the mouth, this space fills up with drool which slowly drips out at the sides, and looks like a moist chewy mouth when in fact it is the same drool as you would produce if forced to hold a large pebble in your mouth.

A horse with nothing in his mouth hardly ever opens the mouth to let air in, unless he eats or whinnies. When the horse has his mouth closed the tongue fills the space between the rows of teeth and the palate, and there''''s nothing to support the idea that when a bit comes into the mouth this changes. The tongue will press the bit up against the palate, although not very hard. So the bit will be in contact with the palate, or your horse will be gaping. So minimum air space in the mouth, and as mouth-contoured a bit as possible, is probably high on the wish list of many horses.

I read somewhere on the internet that the port must not be too wide, or it will lose its effect on the bars and instead hurt the poor tongue. Well...

A narrow port will hurt the tongue - that is the real truth. To think that a tongue will somehow fit into a narrow port so that the bit can act on the bars is absurd. The tongue is thick and wide and for a port not to compress the tongue somewhat and still touch the bars, it needs to have an almost circular port. There are such bits, the Segundos, but I wouldn''''t put such a bit into the mouth of my horse for obvious reasons.

I think this idea originated in some horseman''''s wish for the curb to have some mechanical explanation, that it actually takes leverage against bone. In the absolute majority of cases, it never touches bone, except for the palate. The curb works on the tongue.

Spanish and Western bitting include even higher and narrower ports, sometimes pointed, tassled, with rolls etc, which would pressure up against the palate quite far back and possibly cause tissue damage if used in the modern dressage riding style in which the rider pulls the reins backwards. They use these bits just because spanish and western riders supposedly do not pull on the reins.

This is a self regulating bit. It is made to work in the way that it will apply pressure to the palate by the weight of the shanks. I have superimposed a photo with a catherdral-port bit, both at the vertical, and showing the action when the horse goes above the vertical.

This is serious stuff. Do NOT try this at home, folks! Sure, they do it, and sure it works. But think of the risks. Imagine that your horse is not as well educated as you think. Something scares him and he comes above the bit. Naturally you''''re holding the reins in some fashion, although slack, but when he raises his head like that they snap taut and jab the port into the palate. Or even imagine the rein gets caught in something, and your horse panics. Imagine explaining to your vet why the horse has to be put down because he has a bit pushed into his nasal cavity and it''''s stuck!

This is also why I use a weaker link on my chin chain, when I ride with a curb. Not that I ride with a cathedral port, or anything. I just like safety. I have simply put an old ring from a key chain, you know the kind that you bend open one end of the spring, push the key in, and run it along the crack until it''''s inside the ring. This contruction is weak, but strong enough to be used as a link. Only when an accident happens, it will break before your horse''''s jaw does.

Bit designers have tried to solve this "mouth contour" thing for some time now, and come up with different answers. Such luck for horses! For no two horses are alike. You simply have to try out what fits your horse. Some more expensive curbs come as an assembly kit, where you have different ports to choose from. If you can afford it, this might be the way to go. The only downside is that they have a bolt and nut visible from the outside, and that doesn''''t look so nice, in my opinion.

Around for a long time, has been the Mullen Mouth contour with no actual port, just a slight arch across the whole mouth piece. This is very common in older pelhams and carriage bits, as well as french curbs for the double bridle. The design is simple, but it does not take into consideration the shape of the tongue or anything like that.

Even more common when you look at older bits (and you can guess I have a few) is a sort of port that has no name of its own. It is simply a shallow arch for the tongue, and the mouth piece is thinner above the arch. It''''s like the arch hollows out the bulk of the mouth piece. This neccesitates that the mouth bar is fairly thick to begin with, and that can be a "downer".

A newer invention is the sprenger "lower parts" port, that is, there''''s a marked port which is tongue-shaped and slanted forward. It has been developed to increase champing and submission, and at the same time be softer and adapted for curb introduction in young horses.

I don''''t know. I haven''''t tried it, but it sure looks like the tilted forward port might cause submission by pushing on the palate, or possibly by gripping the tongue. But as I said, I haven''''t tried it. It is more pronounced than it looks from these pictures.