Do you know how tight your curb chain curb chain should be? The standard rule is that you want to be able to fit two fingers comfortably between the chain and your horse. However, this isn't always the magic answer for every horse. Strong horses may need a little more curb to help them rate and stay under control. A relaxed horse that responds on a loose rein may work better on a looser curb that allows the bit to move a little more before the curb engages.