If a bearing rein is too tight, the horses head must be held uncomfortably high. This can result in back pains and problems in horses. A bearing rein is not necessarily bad, but don't put it too tight.

A bearing rein is another term for a checkrein - a strap used to keep horses' heads high, which were fashionable in Victorian England but painful and damaging to a horse's neck.

This is likely the bearing rein, used in horse carriages. The bearing rein was used to force the horses head into an upright carriage to make it look more stylish. However it had bad physical side effects on the horses, including pinched nerves, muscle pain, back problems and breathing trouble. There are other devices that can be used while the horse is being ridden that work similarly to the bearing rein, these include the De Gogue among others.

Anna sewell wrote the book Black Beauty to help get ridd of the bearing rein which hurted horses

It's called a bearing rein but it causes severe pain to the horse and I strongly recommend you don't use it.