Wheel alignment, which includes camber and caster settings, involves the adjustment of the vehicle's suspension in relation to how the tires sit on the road's surface. Camber and caster adjustments use degrees to measure the profile of the tire in two different planes. Camber and caster can effect the wear pattern in tires, and can also determine how straight the vehicle tracks down a road. Manufacturers have different methods for adjusting vehicle alignment. The vehicle owner should know something about how camber and caster affect handling and tire wear.
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Things you need
- Vehicle repair manual (specifications)
- L-shape steel ruler
- Straight edge steel ruler
- Masking tape
Place the vehicle in "park" for an automatic transmission or "neutral" for a manual transmission. Apply the emergency brake. Point the wheels of the vehicle straight ahead; you can look out your driver's side window to see how the left front wheel rim aligns. Align the rim edges so they merge into one solid line. Center your steering wheel, according to the grips and position of the steering wheel emblem.
Stand at the front of the vehicle and look at the angle of the front tires as they point straight ahead. Visualise an imaginary line running from the top of the tire to the ground, which will be the vertical axis. Tilting the tire from the top in either direction indicates the camber angle, always measured in degrees. If the tire points outward, it has a negative camber angle.
Refer to your owner's repair manual for the camber specifications of your vehicle. Generally, a vehicle with a solid rear axle will have a zero-degree camber setting, allowing the tire to sit flat and square on the road. Most front wheel-drive vehicles and standard suspension vehicles have a camber adjustment, and specify a zero degree setting. Some vehicles have adjustments for rear wheel camber and can be adjusted, known as a four-wheel alignment.
Look at the wear patterns on both front tires. Tires that lean inward from the top, or have negative camber, typically wear tires on their inside treads. If your tires appear square with each, facing perpendicular, and you see tire wear on the inside of one or both tires, then they have too much negative camber. If the wear appears on the outside of the tires, the suspension has too much positive camber angle.
Place an L-shaped steel ruler edge-on to your front tire rim. Place another single-edge ruler flat against the top and bottom of the tire rim. Look at the inside angle between both rulers. A noticeable gap points to camber setting, whether the gap appears narrow at the bottom or the top. You can have this angle adjusted at an alignment shop.
Move to one of your front wheels and hang a weighted line from the edge of the bumper lip that runs straight down through the middle of the rim, or axle hub. Use masking tape to secure the line to the bumper. This line represents the forward or rear slant of the vertical line of the upper and lower ball joint pivot points, when used on a wishbone suspension. The ball joints sit just inside the inner part of each front tire and they support the weight of the vehicle.
Visualise that the upper and lower ball joints align with each other on the other side of the wheel in a vertical line. Now imagine that the upper ball joint sits further back toward the rear of the vehicle, offset from the lower ball joint. This condition means the suspension has positive caster, also measured in degrees. You can look up your specifications in your repair manual to find your vehicle's ideal caster setting.
Look at the wheel again and imagine that the upper ball joint sits forward of the lower ball joint. This suspension condition indicates positive caster. The caster setting effects the steering effort balance, and how well the vehicle handles during high speed and cornering. Vehicles that have too much positive caster can actually improve tracking at high speed and aid with cornering, but the effort to move the steering wheel increases when the caster becomes more positive.
Take your vehicle for a test drive. Determine if your vehicle pulls to the left or right when tracking down a straight highway. Temporarily let go of the steering wheel and watch the vehicle movement. If it pulls hard to the left or right, a problem exists with the caster adjustment on one or both wheels. If it takes a while for the vehicle to move to the left or right, this indicates a "drift," but also results from a defective caster setting.
Tips and warnings
- Cross-camber, or cross-caster as set by the manufacturer, means they have set up slight variations from wheel to wheel, which allows for better tracking on vehicles that ride on the right side of the road over a crowned street or highway. The camber is usually set a bit more negative and the caster is set a bit more positive, but only about 1/4 degree or so. This adjustment is deliberate.
- Remember that negative and positive camber -- outside of specifications -- add wear to your tires. Under or over caster settings cause your car to pull in either direction and affect the pressure it takes to move your steering wheel.
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