Notes on front hubs

Notes on front hubs

There is an important feature of the design of the front hub that is applicable to most of the later pre-war Rolls-Royce built chassis. This concerns how the hub is located axially and it is important that this is understood to ensure that the hub is fitted correctly. The hubs to which this applies have an aluminum spacer sleeve between the inner races of the inboard and outboard bearings. In these hubs the inboard bearing is a roller bearing rather than a ball bearing.

The design requires the hub to be located axially on the outboard bearing. The outer track of this bearing should be positively clamped end-wise in the hub, between a shoulder formed in the hub and the grease-cap on the opposite side. The grease-cap is retained by a screwed retainer.

The inner track of the bearing is pulled up tightly by the castle nut on the end of the stub axle. When tight this should clamp the adjacent spacer washer, the aluminium spacer sleeve and inner track of the roller bearing against the inner shoulder on the stub axle. As a test these parts should be assembled on to the stub axle without the hub in place, to make sure that the end nut fully tightens all the parts.

When the hub is fitted the bearings should first be fitted to the hub. When the hub assembly is mounted on the stub axle this can be done by drifting on the outer rim of the hub. However in the case of hubs fitted to the Rolls-Royce axle (not Wraith or Bentley) this may well damage the outer edge of the hub. In addition it may damage the outboard bearing by Brinelling the bearing tracks. At the same time the outboard bearing will tend to creep out of the hub, and this will have to be pulled back in when fitting the grease-cap and retainer. Often it is not possible to generate enough force to do this satisfactorily with the screwed retainer. This results in the hub being positioned too far on to the stub axle, and the bearing not being located positively in the hub.

The best way to fit the hub is to use a short length of tube that will fit over the end of the stub axle and contact the inner race of the outboard bearing. The assembly can then be tapped on to the stub axle via the tube until the inboard bearing is in contact with the inboard location shoulder