As usual Caster wheel tread can be divide into soft caster wheel, and hard tread caster wheels. Most of soft caster wheel are make from soft rubber, Elastic rubber,TPR...which can reduce caster noise and shock absorbing. Which is named as shock absorbing caster. For some high quality equipment such as electronic devices,high precision equipment, and also hospital furniture like hospital bed casters, medical devices casters need use soft tread caster wheels. To keep the equipment safety or reduce noise.
But the weakness of the soft caster is they can not load heavy duty. For heavy duty casters, some times in order to loading heavy duty equipment, we need use hard tread caster wheels. They can bearing heavy duty loading. Such as nylon casters and iron cast wheels, the only defect is they can not provide shock absorbing and may also cause loud noise.