Normally, the lug nuts and studs have right-hand threads (turn clockwise to tighten). When left-hand threads are used, the nut or stud will be marker with an "L." Metric threads will be identified with the letter M or the word Metric.

Figure 8-35.- Drop center wheel.

Figure 8-36.- Semidrop center wheel.

Figure 8-37.- Safety wheel.

Figure 8-38.- Split wheel.

WHEEL BEARING AND HUB ASSEMBLY
Wheel bearings allow the wheel and tire assembly to turn freely around the spindle, in the steering knuckle, or in the bearing support. Wheel bearings are lubricated with heavy, high-temperature grease. This allows the bearing to operate with very little friction and wear.

The two basic wheel-bearing configurations are tapered roller or ball bearing types. The basic parts of a wheel bearing are as follows:

OUTER RACE (cup or cone pressed into the hub, steering knuckle, or bearing support)

BALLS or ROLLERS (antifriction elements that fit between the inner and outer races)

INNER RACE (cup or cone that rests on the spindle or drive axle shaft)

There are two types of wheel bearing and hub assemblies- nondriving and driving. For example, the front wheels on a rear-wheel drive vehicle are nondriving.

Nondriving Wheel Assembly
The components of a nondriving wheel bearing and hub assembly (fig. 8-39) includes the following:

SPINDLE- a stationary shaft extending outward from the steering knuckle or suspension system to which the following components are attached.

WHEEL BEARINGS- normally tapered roller bearings mounted on the spindle and in the wheel hub.

HUB- outer housing that holds the brake disc, or drum, wheel, grease, and wheel bearing.

GREASE WHEEL- a seal that prevents loss of lubricant from the inner end of the spindle and hub.

SAFETY WASHER- a flat washer that keeps the outer wheel bearing from rubbing on and possibly turning the adjusting nut.

SPINDLE ADJUSTING NUT- a nut threaded on the end of the spindle for adjusting the wheel bearing.

NUT LOCK- a thin, slotted nut that fits over the main spindle nut.

DUST CAP- a metal cap that fits over the outer end of the hub to keep grease in and dirt out of the bearings.

Since a nondriving wheel bearing and hub assembly does NOT transfer driving power, the

Figure 8-39.- Disassembled view of a nondriving wheel bearing and hub assembly.

spindle is stationary. The spindle simply extends outward and provides a mounting surface for the wheel bearings. hub. and wheel. With the vehicle moving, the wheel and hub spin on the wheel bearings and spindle. The hub simply freewheels.