Wheel Alignment is the Measurement of complex suspension angles and the adjustment of a variety of suspension components. It is a suspension-tuning tool which greatly influences the vehicle’s handling and tire wear. Wheel Alignment should be checked whenever new tires are installed, suspension components installed, when the vehicle has encountered a major road hazard or curb and any time unusual tire wear patterns appear.
Wheel alignment consists of adjusting the angles of the wheels so that they are parallel to each other and perpendicular to the ground, thus maximizing tire life and ensures straight and true tracking along a straight and level road. The primary static suspension angles that need to be measured and adjusted are caster, camber, toe and thrust angle.
Camber is the angle of the wheel, measured in degrees, if the top of the wheel is tilted out then the camber is positive, if it’s tilted in, then the camber is negative. If the camber is out of adjustment, it will cause premature tire wear on one side of the tire’s thread and can cause a pulling problem to the side.
On most front-wheel-drive vehicles, camber is not adjustable, however there are aftermarket kits that allow sufficient adjustment to compensate for accident damage or the change in alignment due to the installation of lowering springs.
Caster is the angle of the steering pivot, measured in degrees. Viewed from the side, the caster is the tilt of the steering axis. If the caster is out of adjustment, it can cause problems in straight-line tracking, causing the vehicle to pull to the side or to ’wander’ and be difficult to keep in a straight line, or make the steering ’heavy’.
The vehicle’s toe is the most critical alignment setting. A small variation in tow setting of 1/32 inch will result in uneven tire wear and reduce tire life. The toe angle identifies the direction of the tires compared to the centreline of the vehicle. Rear-wheel drive vehicles ’push’ the front tires and resistance causes some drag resulting in rearward movement of the suspension arms against their bushings. Most rear-wheel drive vehicles use positive toe to compensate for suspension movement. Front-wheel drive vehicles ’pull’ the vehicle, resulting in forward movement of the suspension arms against their bushings. Most front-wheel drive vehicles use negative toe to compensate. Toe can also be used to manipulate handling of the vehicle under certain conditions, however excessive toe settings can cause driveability problems, especially in wet road conditions.
Thrust angle is the direction that the rear wheels are pointing in relation to the centerline of the vehicle. The vehicle will ’dog track’ if the thrust angle is not zero and the steering wheel will not be centered. It can also cause the vehicle to handle differently when turning left vs. right. The best solution is to first adjust the rear toe to the centerline and then adjust the front toe. This is done during a 4-wheel alignment if the rear toe is adjustable. If the rear is not adjustable, then the front toe must be set to compensate for the thrust angle, allowing the steering to be centered.
SAI is the measurement in degrees of the steering pivot line when viewed from the front of the vehicle. When added to the camber, the SAI forms the included angle and causes the vehicle to lift slightly when the wheel is turned from a straight position. The vehicles weight pushes down and causes the steering wheel to return to the center when you let go of it after making a turn. Like caster, it provides directional stability and also reduces steering effort. If the Steering Axis Inclination (SAI) is different from side to side, it will cause a pull at very slow speeds.
SAI is a non-adjustable angle. The most likely cause for Steering Axis Inclination (SAI) being out of specification is bent parts, which have to be replaced to correct the condition.
Pro Car Care 4U has the latest in Imaging Wheel Alignment technology, providing accurate and real-time measurements and easy-to-understand printouts of before and after readings. Our staff have over 10 years’ experience in performing wheel alignments and have been trained by the equipment manufacturer in order to maximize customer satisfaction. For a limited time we are offering a FREE alignment check with any oil change package. So call to book your alignment check or oil change today!