The steering system on your car is an important and part and due to the UK road conditions need checking every 6 months or if you notice problems. Out-of-alignment conditions occur when the suspension and steering systems are not operating at their desired angles The steering rack on all motor vehicles is easily knocked out of alignment by all the speed humps and potholes or even by changing the suspension on the vehicle. When the wheel alignment becomes out of tolerance the tyres will wear unevenly on either edge of the side walls.
If you notice any of these faults on your vehicle we recommend you have your wheel alignment / tracking checked and adjusted if necessary. Our highly trained technicians can be of assistance to advise you of the best solution for any steering geometry problems.
At R-Tec we offer complete wheel alignment not just simple tracking which most garages offer you.
Types of alignment - Types of alignments offered today are front-end, thrust angle, and four-wheel. During a front-end alignment, only the front axle's angles are measured and adjusted. Front-end alignments are fine for some vehicles featuring a solid rear axle, but confirming that the front tyres are positioned directly in front of the rear tyres is also important.
On a solid rear axle vehicle, this requires a thrust angle alignment that allows the R-Tec technician to confirm that all four wheels are "square" with each other. Thrust angle alignments also identify vehicles that would "crab" going down the road with the rear end offset from the front.
On all vehicles with four-wheel independent suspensions, or front-wheel drive vehicles with adjustable rear suspensions, the appropriate alignment is a four-wheel alignment. This procedure "squares" the vehicle like a thrust angle alignment, and also includes measuring and adjusting the rear axle angles as well as the front.
Not all vehicles are easily adjustable or fully adjustable. Some vehicles require aftermarket kits to allow sufficient adjustment to compensate for accident damage or the change in alignment due to the installation of lowering springs.
When aligning a vehicle, it's appropriate for the vehicle to be carrying its "typical" load. This is important for drivers who continuously carry loads in their vehicles, such as sales representatives with samples or literature in the trunk.
The primary static suspension angles that need to be measured and adjusted are caster, camber, toe and thrust angle.
Here's a definition of each angle and its influence on a vehicle and its tyres.
The camber angle identifies how far the tyre slants away from vertical when viewed directly from the front or back of the vehicle. Camber is expressed in degrees, and is said to be negative when the top of the tyre tilts inward toward the center of the vehicle and positive when the top leans away from the center of the vehicle.
Since normal car suspension cannot completely compensate for the outer tyre tipping towards the outside when the vehicle leans in a corner, there isn't a magical camber setting that will allow the tyres to remain vertical when traveling straight down the road (for more even wear), and remain perpendicular to the road during hard cornering (for more generous grip).
Different driving styles can also influence the desired camber angle as well. An enthusiastic driver who corners faster than a reserved driver will receive more cornering grip and longer tyre life from a tyre aligned with more negative camber. However with the aggressive negative camber, a reserved driver's lower cornering speeds would cause the inside edges of the tyres to wear faster than the outside edges.
What's the downside to negative camber? Negative camber leans both tyres on the axle towards the center of the vehicle. Each tyre develops an equal and offsetting "camber thrust" force (the same principle that causes a motorcycle to turn when it leans) even when the vehicle is driven straight ahead. If the vehicle encounters a bump that only causes one tyre to lose some of its grip, the other tyre's negative camber will push the vehicle in the direction of the tyre that lost grip. The vehicle may feel more "nervous/ skittish " and become more susceptible to tramlining. Excessive camber will also reduce the available straight-line grip required for rapid acceleration and hard stops.
Appropriate camber settings that take into account the vehicle and driver's aggressiveness will help balance treadwear with cornering performance. For street-driven vehicles, this means that tyre wear and handling requirements must be balanced according to the driver's needs. The goal is to use enough negative camber to provide good cornering performance while not requiring the tyre to put too much of its load on the inner edge while traveling in a straight line. Less negative camber (until the tyre is perpendicular to the road at zero camber) typically will reduce the cornering ability, but results in more even wear.
Even though they have some of the most refined suspensions in the world, the next time you see a head-on photo of a Formula 1 car you will notice how much negative camber is dialed into the front wheels. While this is certainly an example of wear not being as important as grip, negative camber even helps these sophisticated racing cars corner better.
The caster angle identifies the forward or backward slope of a line drawn through the upper and lower steering pivot points when viewed directly from the side of the vehicle. Caster is expressed in degrees and is measured by comparing a line running through the steering system's upper and lower pivot points (typically the upper and lower ball joints of an A-arm or wishbone suspension design, or the lower ball joint and the strut tower mount of a McPherson strut design) to a line drawn perpendicular to the ground. Caster is said to be positive if the line slopes towards the rear of the vehicle at the top, and negative if the line slopes towards the front.
A very visual example of positive caster is a motorcycle's front steering forks. The forks point forward at the bottom and slope backward at the top. This rearward slope causes the front tyre to remain stable when riding straight ahead and tilt towards the inside of the corner when turned.Caster angle settings allow the vehicle manufacturer to balance steering effort, high speed stability and front end cornering effectiveness.
Increasing the amount of positive caster will increase steering effort and straight line tracking, as well as improve high speed stability and cornering effectiveness. Positive caster also increases tyre lean when cornering (almost like having more negative camber) as the steering angle is increased.
What's the downside to positive caster? If the vehicle doesn't have power steering, a noticeable increase in steering effort will be felt as positive caster is increased. Other than that, the effects of positive caster are pretty much "positive," especially increasing the lean of the tyre when the vehicle is cornering while returning it to a more upright position when driving straight ahead.
A rear-wheel drive vehicle "pushes" the front axle's tyres as they roll along the road. Tyre rolling resistance causes a little drag resulting in rearward movement of the suspension arms against their bushings. Because of this, most rear-wheel drive vehicles use some positive toe-in to compensate for the movement, enabling the tyres to run parallel to each other at speed.
Conversely, a front-wheel drive vehicle "pulls" the vehicle through the front axle, resulting in forward movement of the suspension arms against their bushings. Therefore most front-wheel drive vehicles use some negative toe-out to compensate for the movement, again enabling the tyres to run parallel to each other at speed.
Toe can also be used to alter a vehicle's handling traits. Increased toe-in will typically result in reduced over steer, help steady the car and enhance high-speed stability. Increased toe-out will typically result in reduced under steer, helping free up the car, especially during initial turn-in while entering a corner.
Before adjusting toe outside the vehicle manufacturer's recommended settings to manipulate handling, be aware that toe settings will influence wet weather handling and tyre wear as well.
Excessive toe settings often bring with them drivability problems, especially during heavy rain. This is because the daily pounding of lorrys on many roads which leave ruts that fill with water. Since excessive toe means that each tyre is pointed in a direction other than straight ahead, when the vehicle encounters a puddle that causes only one tyre to lose some of its grip, the other tyre's toe setting will push (excessive toe-in) or pull (excessive toe-out) the vehicle to the side. This may make the vehicle feel unsettled and very "nervous / skittish."
Additionally the vehicle's toe is one of the most critical alignment settings relative to tyre wear. A toe setting that is just a little off its appropriate setting can make a huge difference in their wear. Consider that if the toe setting is just 4mm off of its appropriate setting, each tyre on that axle will scrub almost 2 metres sideways every mile! Extend it out and you'll discover that rather than running parallel to each other, the front tyres will scrub over 1/4-mile sideways during every 100 miles of driving! Incorrect toe will reduce you of tyre life.