There are four basic types of wheel systems:
- Cast spoke
- Steel disc
- Aluminum disc
- Wide-base disc
Cast spoke wheels, used almost universally through the 1970s, are much less popular today than disc wheels (both steel and aluminum). Wide-base disc wheels have been principally used on front axles of some extra-heavy-duty applications such as construction trucks. Their popularity is slowly increasing, though, and they are occasionally observed as supersingles replacing sets of duals. Wide-base-singles can offer slightly improved fuel economy so their use is predicted to increase over the next few years. Truck wheels are mounted to axles by what is known as the wheel end. Understanding wheel end procedure is critical for truck technicians because so many vehicle safety issues depend on this.