There are some very basic principals to follow when setting the wheel alignment, but achieving the perfect alignment is a very personal thing. Everyone is different and with those differences come different uses, driving styles and requirements. A wheel alignment can be changed to compliment a customer's needs and their expectations.
Before beginning a street alignment, here are some important aspects to consider.
- What kind of vehicle is it? ( Sedan, Ute, SUV)
- Does it have pre-existing tyre wear issues?
- Does it carry constant load or varying loads?
- What kind of road surfaces does it mostly drive on? ( Highway, City )
- What is the customer's driving style?
- Focussed on tyre conservation
- Focussed on maximum grip/handling
- What is the main use for this vehicle?
- Is the vehicle in a good alignable condition?
- What aftermarket parts are fitted to the vehicle? (Suspension, Steering)
- Does the vehicle pull to one side?
If the vehicle is used for motorsport most of the above still applies along with:
- What class of motorsport ( Circuit, Drift, Rally, Drag etc)
- What feedback can you get from the customer
- Does it oversteer?
- Does it understeer?
- Does it lack grip under brakes?
- Does it lack grip under power?
Some might say that a lot of this is irrelevant for street driven cars as manufacturers will recommend an alignment specification for each model - and most alignment technicians will use this as a good benchmark. In an ideal world this should be true however these recommended settings very rarely take into account real world conditions. something as simple a road surface being banked or sloped off to one side or another to help disperse rain water can cause a vehicle to also follow that shape in the road if the wheel alignment isn't setup correctly to counter this. At Hakon Suspension Melbourne we take all of this into consideration before proceeding with our comprehensive wheel alignments.
Now to explain Wheel alignments in a little more depth; “Wheel alignment” is an inclusive term referring to the primary and secondary wheel angles and measurements. In this post i will be talking about primary angles. The full list of angles are
- SAI (Steering Axis Inclination)
- Included angle
- Toe out on turns
- Maximum Turns
- Subframe Angle
- Track Width
- Ride Height
Also measured in degrees, Castor is measured by comparing a line drawn between the upper and lower steering pivot points ( generally a upper and lower balljoint or lower ball joint and upper strut mount ) to a line drawn through the centre line of the wheel perpendicular to the ground. If the line between the two pivot points is leaning back towards the rear of the car then it is said to be positive castor if it is leaning forward to the front of the car it is said to be negative castor.
Castor is used to balance Steering input effort, high speed stability and cornering effectiveness.
Increasing positive castor increases straight line stability, and will make the steering feel heavier and will aid with the steering naturally returning to centre. It also induces ‘dynamic camber’ during cornering, by offsetting the steering pivot points it will cause the outside wheel to lean in ( Negative Camber ) out ( Positive camber ) on the inside wheel, increasing cornering ability.
Decreasing castor or running a very low castor angle will have an opposite effect to increasing castor and is generally used to create a light steering feel in older vehicles with no power assisted steering.
Camber is measured in degrees and identifies how much the wheel and tyre leans away from vertical when viewed from directly behind or in front of the wheel, The Camber is said to be negative when the top leans inwards towards the body of the vehicle and positive when it leans outwards away from the vehicle.
Different camber settings can balance out front and rear understeer/oversteer issues through cornering however too much negative camber on your drive axle will reduce the tyre contact patch with the road and grip levels under acceleration.
Excessive negative camber also causes ‘Camber thrust’ when both wheels are set to negative camber they force against each other which is ok as long as both wheels are in contact with the road surface, if grip is lost on one wheel it will result in the vehicle being pushed or thrust towards that wheel - this can be commonly referred to as tram tracking.
Toe identifies the direction the wheels are pointing in relation to the centre line of the vehicle when viewed from above, Toe can be expressed in degrees or fractions of an inch but is more commonly referred to in millimetres.
Toe can be used to alter a vehicles handling characteristics, Toe In ( Positive ) can result in reduced oversteer and help steady the car and enhance high-speed stability. Toe Out ( Negative ) can result in reduced understeer and will help free up the car during initial turn-in on a corner.
Toe can have the biggest effect on tyre wear and stability in a normal street driven application and particular care should be taken when putting the correct toe setting into a vehicle.
Feel free to give us a call anytime on 03 9305 1448 to book your vehicle in for one of our comprehensive alignments.
15 Fleet St
- June 07, 2016
- Hakon Sales