A curb rein is the lower of the two reins used when riding with a double bridle or pelham bit. It attaches to the lower ring of the bit and, when applied, engages the curb chain beneath the horse’s chin groove, creating leverage and poll pressure. The curb rein is a precise, powerful aid and is used sparingly — it is the refinement rein, used in conjunction with the snaffle (or bridoon) rein to achieve subtle communication at higher levels of training.
How a Curb Rein Works
When the rider takes contact on the curb rein, the shank of the bit rotates. This action simultaneously tightens the curb chain against the chin groove, lowers the bit in the mouth, and applies pressure to the poll via the headpiece. The combination of these three pressure points — chin groove, mouth, and poll — creates a distinctive action quite different from a plain snaffle.
The degree of leverage depends on the length of the shank below the mouthpiece. A longer shank produces more leverage with less rein movement; a shorter shank is less severe. This is why bit selection and correct fitting of the curb chain are critical — a chain that is too loose will flap ineffectively, while one that is too tight will activate too quickly and cause discomfort.
The Double Bridle and Rein Handling
In a double bridle, the rider holds four reins — two bridoon reins and two curb reins. The most common method is to hold the bridoon rein between the index and middle finger, and the curb rein between the little finger and ring finger, or to carry all four in the conventional way with the curb rein outside the bridoon. This takes practice to master and is taught progressively.
The bridoon rein maintains the primary contact and is used for most directional and pace-controlling communication. The curb rein adds subtlety — a slight squeeze communicates collection, engagement, and flexion. A rider who relies on the curb rein as their primary contact is misusing the double bridle. For more on the relationship between rider hands and bit action, see our entry on the false rein.
When Is a Curb Rein Used?
The curb rein is most commonly encountered in:
- Dressage at advanced levels — from Medium level upwards, the double bridle is introduced and becomes obligatory at Grand Prix
- Showing classes — many ridden show horse classes, particularly hacks and hunters, are ridden in a double bridle
- Western riding — western curb bits (shanked bits with a single rein) are used differently but also operate on curb chain principles
- Pelham bridles — the pelham combines snaffle and curb action in a single bit, using two reins or roundings
The FEI dressage rules specify the bits and equipment permitted at each level. See fei.org for the full equipment regulations.
Fitting the Curb Chain
The curb chain should lie flat in the chin groove, twisted so that each link lies flat against the skin. It should allow two fingers to be inserted between chain and chin groove when the shank is at 45 degrees. The lip strap, if used, passes through the fly link of the curb chain and attaches to small rings on the shank, preventing the chain from riding up.
An incorrectly fitted curb chain is a common cause of resistance, head tossing, and unwillingness to work through in horses ridden in a double bridle. Any horse showing these signs should have the entire bridle checked by an experienced instructor or horse dentist before any training adjustments are made.
Frequently Asked Questions
Can a beginner rider use a curb rein?
A curb rein should only be used by riders with an independent, quiet seat and established soft hands. The leverage action of a curb bit is powerful, and inconsistent or heavy contact can cause significant discomfort. Beginners learn on plain snaffle bridles and progress to double bridles only once they have the control and feel required.
What is the difference between a curb rein and a bridoon rein?
In a double bridle, the bridoon rein connects to the small snaffle bit (the bridoon) and provides the primary rein contact. The curb rein connects to the lower ring of the curb bit and engages the leverage and curb chain action. The two work together — the bridoon maintains rhythm and direction, the curb adds refinement and collection.
Is a pelham the same as a double bridle?
No. A pelham is a single bit that combines snaffle and curb action using two rings on the same mouthpiece. A double bridle uses two separate bits — a bridoon and a curb bit — each with their own rein. The double bridle gives the rider more independent control of each action; the pelham is a simpler alternative often used with horses that go well in combined action.