I had all four wheels aligned and not just the front.
Quote:I had all four wheels aligned and not just the front.
to the best of my knowledge there is no adjustment on the rear wheels of cars.
There are two main types of 4-wheel alignments. In each case, the technician will place an instrument on all four wheels. In the first type the rear toe and tracking is checked, but all adjustments are made at the front wheels. This is done on vehicles that do not have adjustments on the rear. The second type is a full 4-wheel alignment where the adjustments are first made to true up the rear alignment, then the front is adjusted. A full 4-wheel alignment will cost more than the other type because there is more work involved.
The type of alignment performed usually is conditional upon the amount of adjustment that's feasible on a particular vehicle, as well as the shop's equipment capability. On solid-axle, rear-wheel-drive (RWD) vehicles, for example, a thrust alignment is usually performed so the front wheels are aligned to the rear axle. The drive direction of the rear axle is referred to as the thrust line, which should in theory be the same as the geometric center of the vehicle.
A four-wheel alignment involves adjusting the rear wheels to achieve proper camber and toe and a thrust angle as close to zero as possible, then adjusting the front wheels to the same vehicle centerline. Four-wheel alignments are recommended for most front-wheel-drive cars, mini-vans, some sport utility vehicles and RWD vehicles with independent suspension.
Many alignment shops today offer a standard thrust alignment and charge extra for time and materials if rear-wheel adjustments are required. This approach eliminates different vehicle owners paying the same price, when only one of them requires rear-wheel alignment.
To perform a four-wheel alignment, a four-sensor machine is required. Turnplates or rear slip plates at all four corners are needed during both four-wheel and thrust alignments. The rear wheels must be allowed to relax to their normal position to achieve proper readings whether they are to be adjusted or not.
Today's computerized alignment equipment can identify and graphically display the alignment capabilities of a vehicle by make and model. In addition, the machine will do all the mental gymnastics of shim selection and orientation, which leaves the technician free to do what he or she does best - diagnose and correct the alignment problem.
Some newer model alignment machines feature cordless sensors that use high-frequency transmitters instead of cables to send data to the console. Other new features include a ride height option that shortens measurement time to just a few seconds per wheel and provides on-screen videos to illustrate the adjustment method on the vehicle being serviced. Some machines use a laser, similar to a pointer, for toe measurement.
In addition to providing caster, camber and toe readings, alignment machines can be used as a diagnostic tool. Diagnostic angles such as steering axis inclination (SAI), included angle (IA), setback and turning radius can help the technician to identify problems that otherwise might be overlooked.