Understanding wheel alignment and geometry (drop & drag)

Castor angle

Castor is defined as the ​ (a)   between the steering axis and an imaginary vertical line, as viewed from the​ ​​ (b)   of the vehicle. This angle is essential for providing ​ (c)   stability and a self‐​ (d)   effect to the steering. A castor angle helps the wheels return to a straight position after a turn, but excessive​ (e)   castor may result in heavier steering and increased return effort.​ ​ ​ ​ ​

• angle
• steering
• centring
• side
• positive
• negative
• offset
• top

Camber angle

Camber describes the tilt of a wheel relative to the vertical axis when viewed from the ​ (a)   of the vehicle. When the top of the wheel leans ​ ​ (b)   , it is known as negative camber, which can enhance ​ (c)   performance by keeping more of the tyre in contact with the road during a turn. Conversely, positive camber can improve straight‐line ​ (d)   but may compromise grip during cornering. Adjusting camber is a critical part of overall ​ (e)   alignment

• above
• straight line 
• instability
• front
• inwards
• cornering
• stability
• wheel

Toe angle

Toe refers to the angle at which the wheels are set relative to the vehicle’s ​ (a)   axis. When the fronts of the wheels are closer together than the rears, the wheels are said to have ​ (b)   ; if the fronts are farther apart, it is known as ​ (c)   . Correct toe alignment is vital for balanced handling because improper toe settings can lead to increased ​ (d)   wear and reduced overall ​ (e)   . Maintaining the proper toe ensures optimal tyre contact with the road surface.

• centre line
• toe in
• toe out
• tyre
• stability
• parallel
• instability
• thrust

Ackermann angle

Ackermann steering geometry is a design concept that ensures the wheels follow ​ (a)   turning paths. To achieve this, the inner and outer wheels must turn at different angles, which minimizes ​ (b)   and reduces tyre scrubbing during a turn. This is accomplished by positioning the steering pivot points so that they converge at a point along the extended ​ (c)   of the rear axle. The resulting setup helps in minimizing slip angles and maximizing steering efficiency.​ This principle also known as toe out on turns (TOOT) ensures that during a turn, the ​ (d)   wheel (which follows a tighter radius) turns at a greater angle than the ​ (e)   wheel to prevent tyre scrubbing and improve handling. The idea is that both wheels follow their respective arcs correctly, reducing slip and wear.

• different
• tyre scrub
• centre line
• inner
• outer
• Indifferent 
• thrust

Thrust angle

The thrust angle is the angle formed between the ​ (a)   of the vehicle and the direction the ​ (b)   is pointing. Ideally, the thrust angle should be zero, meaning the rear wheels are perfectly aligned with the front wheels. If the thrust angle is misaligned, the vehicle may pull to one side, causing uneven tyre wear and affecting stability. Thrust angle misalignment can result from a ​ (c)   , improper suspension alignment, or damage from an accident. Correcting the thrust angle ensures that the vehicle ​​ (d)   straight and improves overall handling​ .

• centreline
• rear axle
• bent axle
• tracks
• front axle
• straight axle

Steering Axis Inclination (SAI)

Steering Axis Inclination (SAI) is the angle formed between the steering axis and a vertical line when viewed from the ​ (a)   of the vehicle. This angle is built into the suspension geometry and helps improve straight-line stability and steering returnability. A proper SAI angle reduces steering effort and enhances vehicle handling, but if misaligned, it can cause pulling to one side and affect overall control. SAI is a ​ (b)   angle and is not adjustable on most vehicles, meaning any misalignment typically indicates bent suspension components.

Included Angle

The included angle is the sum of the Steering Axis Inclination (SAI) and the camber angle. It helps technicians diagnose issues with suspension geometry. If the included angle is outside the manufacturer’s specifications but SAI is correct, it indicates a camber issue. If both the included angle and SAI are incorrect, it suggests possible bent or damaged suspension components. Checking the included angle is crucial for ensuring proper wheel alignment and safe handling

• front
• fixed
• adjustable 
• rear

Wheel alignment

When performing a wheel alignment check, the ​ (a)   capacity and specified ​ (b)   weights must be accounted for, as inaccurate adjustments could lead to uneven tyre wear and negatively impact vehicle handling.

• fuel
• oil
• vehicle
• load
• unload