Tapered roller bearings are the most basic and widely used tapered bearing .And they have tapered inner and outer ring raceways between which tapered rollers are arranged. This type of bearings is particularly suitable for carrying of combined (radial and axial) loads. The axial load carrying capacity of the bearings is largely determined by the contact angle the larger contact angle， the higher the axial load carrying capacity. It is usually fitted as one of an opposing pair. When assembled， single-row tapered roller bearings can be set to the required clearance or preload condition to optimize performance