AWD Alignment Tips What To Do, Why To Do It - Garage

Tip 2: Tune Your Toe
Toe is the direction a car's tires are pointed relative to each other when viewed from above. Toe-in means the front of the tires are closer to each other than the rears. Toe-out is the opposite. Fine-tuning toe settings allow a measure of control that's often overlooked. It also has a significant affect on how a car behaves in a corner. Front toe settings make a big difference in how a car handles during the first third of a turn, the critical turn-in phase where cornering force is initiated. Rear toe settings are critical for helping an AWD car get on the gas while exiting a corner harder and sooner. Excessive toe-in or toe-out will cause tire wear on the outside and inside edges of the tire respectively and can ruin one very quickly. Any toe setting past an 1/8-inch either way has a negative affect on tire life. Too much toe has probably ruined more tires on lowered cars than just about any other attribute, including camber.

Tip 3: Adjust Caster
Every car's front wheels steer on pivots attached to the suspension. Caster is the angle from vertical of an imaginary line drawn through the spindle's pivots, measured in degrees. The caster is positive if the top pivot point is behind the lower pivot point, meaning the caster angle slopes backward like on a bicycle (as viewed from the side). If the angle slopes forward, the caster is negative. No cars have negative caster so don't worry about it.

Increasing positive caster projects the point where the steering axis meets the ground further in front of the tire's contact patch. This distance is called caster trail. When the tire's contact patch is behind this point, the tires want to stay centered behind it, much like a shopping cart's casters naturally lining up in the direction of travel with the wheel's contact patch behind the caster's pivot point. Like the shopping cart caster, the lever arm created between this point and the tire's contact patch creates torque, which causes the steering to self-align in a forward direction. The driver perceives this self-aligning reaction as greater stability and on-center steering feel.

Lots of positive caster causes the outside wheel to gain beneficial negative camber in a turn. Think of a parked chopper with the wheel flopped to the side. That's an extreme example of negative camber gain with positive caster. But excessive positive caster can be a bad thing. Too much can increase torque steer on AWD cars, especially if there's excessive wheel offset. Too much caster can also increase understeer due to the lifting and tipping of the tire. Caster can be adjusted with camber plates, anti-lift caster kits and various tension arms.

Tip 4: Corner balance
Corner balancing is the adjusting of the weight of all four wheels so the right to left and left to right crossweight percentages are equal diagonally across the car. This is done so a car's understeer/oversteer balance is the same in both right- and left-hand turns. It's an important step in chassis setup but is often ignored by all but the savviest tuners. Corner balancing is one of the main advantages a coilover suspension offers when compared to a stock-type spring suspension kit. Corner weights are adjusted by rolling a car up onto electronic scales that weigh each wheel individually. With the driver's weight in the car, the spring perches are adjusted; raising the perch increases the weight of the adjusted wheel, lowering decreases it. The weights are fiddled until they're as close to equal from side-to-side as possible with equal crossweights.