Adjustment of the Headstall – Bit – Curb

With your headstall and bit on a horse, and with the curb loose, adjust the headstall so that the mouthpiece of the bit just makes contact with the upper curve of the lip. This will be the starting point as each horse is different.

Once the headstall and bit are adjusted, then the curb can be adjusted to make contact on the chin when the reins are picked up. To check the adjustment, stand beside your horse and pickup on both reins to check the curb makes contact, and then releases when rein contact is loosened. Make sure the horse understands curb pressure and does not overreact if they have not had contact on the chin before.

If the rein rotates the cheek to a point that it becomes an extension of the rein, then the curb needs to be tighter. 

If you ride with some outside rein, versus only inside rein, the curb needs to be adjusted. In general, the less outside rein the tighter the curb. 

For a gag bit (numerous designs) the curb should be tightened, so the mouthpiece does not slide up past the one-to-one ratio of the cheek, this will also depend on how much the outside rein is being used.

From this point on, you can adjust the headstall and curb to see where your horse is most comfortable (process of elimination).