Wheel Alignment

Aligning a vehicle's front wheels is the job of balancing the steering angles with the physical forces being exerted. The steering angles are; caster, camber, toe-in, steering axis inclination, and toe-out on turns. The physical forces are gravity, momentum, friction, and centrifugal force. Since so many factors are involved in front wheel alignment, it is also called front end alignment, steering alignment, steering balance, or steering geometry. Alignment is more than just adjusting the angularity of the front wheels. With steadily increasing production of front wheel drive vehicles with independent rear suspension, four wheel alignment is often required. For ideal wheel alignment, certain conditions would have to be met. Both front tires will be the same brand, size, and type. Each will have the same degree of tread wear, and be inflated with the same pressure. Each wheel is properly and equally adjusted for angularity, each tire will maintain the same area of tread contact on a smooth road surface. Obviously, it is impossible to maintain all these requirements. The steering control rods are used to adjust toe-in and toe-out. The upper and/or lower control arms are adjusted to affect the camber angle. Caster is usually not adjustable. With all the weight balance factors to be checked out and corrected, it is obvious that wheel alignment is more than just an adjustment of the steering angles. The whole theory of wheel alignment revolves around balanced weight distribution on the wheels and proper tire tread contact with the road surface while the vehicle is in motion.

Wheel (Slave) Cylinder

The wheel cylinder, also called the brake cylinder or slave cylinder, is a cylinder in which movable piston(s) convert hydraulic fluid pressure into mechanical force. The piston(s) within the cylinder move the brake shoes or pads against the braking surface of the drum or rotor. There is one cylinder (or more in some systems) for each wheel. The cylinder is usually made up of a single-bore cylinder casting, an internal compression spring, two pistons, two rubber cups or seals, two rubber boots to prevent entry of dirt and water, and a bleeder screw (valve). In drum type brakes, the wheel cylinder is fitted with push rods that extend from the outer side of each piston through a rubber boot, where they bear against the toe end of each brake shoe. In disc brakes, the wheel cylinder is part of the caliper. As the brake pedal is depressed, it moves pistons within the master cylinder, forcing hydraulic brake fluid through the brake lines and into cylinders at each wheel. The fluid under pressure causes the wheel cylinders' pistons to move, which forces the shoes or pads against the brake drums or rotors. Two-way pressure is applied when the wheel cylinder is activated. Brake fluid enters the center of the cylinder, forcing the pistons apart. Pushrods at the piston ends then apply equal pressure to the brake shoes. A return spring pulls the pistons together when pressure is released.

Wheels

Wheels come in many different designs and usually fall into two categories: stamped sheet metal and machine castings. Some wheels are a combination of the two. Usually cast alloy wheels are higher priced, but have greater strength than stamped sheet metal wheels. Stamped sheet metal wheels are the most common, because they are less expensive to produce and are adequate for most uses. Some cars have wire wheels which consist of three basic components; inner rings, outer rings, and a series of spokes which connect the two. Cast aluminum wheels are very popular, magnesium wheels are also popular. Both are popular because they are light-weight and strong.