The following information was supplied by the John Bean 5 series alignment machine. The information is not meant to be passed as being my own and all credit goes to the John Bean company and it's associates. Information I add will be notated as follows: *** Text ***
-Caster
The function of CASTER is to aid proper steering stability. The greater the CASTER, the more the vehicle's steering will try to return to straight ahead. CASTER provides this by tilting the vehicle's steering pivot axis to the front or the rear. This axis is an imaginary line drawn through the upper and lower steering pivot points when the vehicle is viewed from the side. These pivot points can be the upper and lower ball joints on an SALA suspension system. On strut equipped vehicles, they are the lower ball joint and the upper bearing plate. As viewed from the side, the line drawn through the steering pivots compared to a true vertical is CASTER. If the top of this line is tilted to the rear of the vehicle, the CASTER is said to be positive.
-SAI (Steering Axis Inclination)
SAI, along with CASTER, provides steering stability and steering wheel return to straight ahead. SAI is often called a diagnostic angle because it, along with CAMBER can be used to diagnose damaged or worn suspension components. When SAI and CAMBER are added together, the INCLUDED ANGLE is formed. When SAI is out of specs, CAMBER should be measured and added (if positive) or subtraced (if negative) to get the INCLUDED ANGLE. Refer to the service manual for charts which aid in diagnosing problems using these angles.
SAI is not usually adjustable, although it can change as other adjustments are performed. CMABER should be adjusted as close to specs as possible, before calculating the INCLUDED ANGLE.
-SAI (Steering Axis Inclination)
SAI, Like Caster is a measure of the vehicle's steering axis. SAI is the angle of the steering axis from the vertical, when viewed from the front. SAI angle is always positive, in other words the upper steering pivot is always closer to the vehicle's center than the lower.
SAI will cause the spindle to try to pivot downward as the wheels are steered away from the straight ahead. Since it cannot go downward, this raises the vehicle. Gravity then makes the vehicle settle, or steer back to straight ahead.
-Camber
A tire may be straight up and down, or it may lean so it is in or out at the top. This condition is called CAMBER. If the tire leans IN at the top, so it is towards the vehicle, this is NEGATIVE CAMBER, and the minus sign (-) is used. If the tire leans OUT at the top, CAMBER is positive. Straight up is zero (0). If a CAMBER reading is zero, it does not mean "no reading", it is an actual measurement, and is often a specification. CAMBER is measured as an angle from straight up (true vertical). It is measured in degrees.
-Camber Causing Pull
If a tire is leaned slightly, and rolled, it trys to roll in the direction of the lean. Thus, CAMBER can create a pull or lead in a vehicle. If CAMBER is the same on each side of the vehicle, the pulls will cancel each other, but if different, the vehicle should pull towards the side with the most positive CAMBER.
CAMBER is sometimes used to correct a minor pull problem, especially with front wheel drive vehicles. Due to manufacturer's tolerances on their specifications, some amount of adjustment is permitted. If pulling LEFT, increase right side CAMBER, or decrease left CAMBER. If pulling RIGHT, increase left side CAMBER, or decrease right CAMBER.
-Cross Camber
CROSS CAMBER is the difference between the left and right CAMBER readings. CROSS CAMBER can cause a pull. Often, this can happen even when both CAMBER readings are within specification, particularly if the tolerance (+/-) is large. For this reason, more and more manufacturers are specifying maximum CROSS CAMBER and CROSS CASTER values.
-Toe
TOE settings during driving should be straight ahead. During driving, normal forces may cause the TOE settings to be different than when the vehicle sits on the alignment rack. For this reason, manufacturer's specifications are usually near zero but not at zero. Incorrect TOE settings cause the tire to roll at an angle. This is the leading cause of tire wear!
TOE IN (Front of tires is closer together) is positive.
TOE OUT (rear of tires is closer together) is negative.
TOE should be adjusted after CASTER and CAMBER.
-How Toe Is Diagnosed
Your FMC Visualiner can diagnose and correct TOE problems before tire damage is done **** that was info specifically for alignment machine**** If however, a vehicle has been driven with improper TOE, the wear pattern on the tire will tell the story.
Excessive TOE IN will cause the increased wear on the outside edges, and the tread will often be saw toothed. When rubbing the tire with your hand from the inside towards the outside, the sharp edges will be felt.
Excessive TOE OUT will cause increased wear on the inside edge, and if saw toothed, the effect can be felt by rubbing from the outside to the inside. Badly misadjusted TOE can also cause: wander, poor handling, and a crooked steering wheel.
-Caster
The function of CASTER is to aid proper steering stability. The greater the CASTER, the more the vehicle's steering will try to return to straight ahead. CASTER provides this by tilting the vehicle's steering pivot axis to the front or the rear. This axis is an imaginary line drawn through the upper and lower steering pivot points when the vehicle is viewed from the side. These pivot points can be the upper and lower ball joints on an SALA suspension system. On strut equipped vehicles, they are the lower ball joint and the upper bearing plate. As viewed from the side, the line drawn through the steering pivots compared to a true vertical is CASTER. If the top of this line is tilted to the rear of the vehicle, the CASTER is said to be positive.
-SAI (Steering Axis Inclination)
SAI, along with CASTER, provides steering stability and steering wheel return to straight ahead. SAI is often called a diagnostic angle because it, along with CAMBER can be used to diagnose damaged or worn suspension components. When SAI and CAMBER are added together, the INCLUDED ANGLE is formed. When SAI is out of specs, CAMBER should be measured and added (if positive) or subtraced (if negative) to get the INCLUDED ANGLE. Refer to the service manual for charts which aid in diagnosing problems using these angles.
SAI is not usually adjustable, although it can change as other adjustments are performed. CMABER should be adjusted as close to specs as possible, before calculating the INCLUDED ANGLE.
-SAI (Steering Axis Inclination)
SAI, Like Caster is a measure of the vehicle's steering axis. SAI is the angle of the steering axis from the vertical, when viewed from the front. SAI angle is always positive, in other words the upper steering pivot is always closer to the vehicle's center than the lower.
SAI will cause the spindle to try to pivot downward as the wheels are steered away from the straight ahead. Since it cannot go downward, this raises the vehicle. Gravity then makes the vehicle settle, or steer back to straight ahead.
-Camber
A tire may be straight up and down, or it may lean so it is in or out at the top. This condition is called CAMBER. If the tire leans IN at the top, so it is towards the vehicle, this is NEGATIVE CAMBER, and the minus sign (-) is used. If the tire leans OUT at the top, CAMBER is positive. Straight up is zero (0). If a CAMBER reading is zero, it does not mean "no reading", it is an actual measurement, and is often a specification. CAMBER is measured as an angle from straight up (true vertical). It is measured in degrees.
-Camber Causing Pull
If a tire is leaned slightly, and rolled, it trys to roll in the direction of the lean. Thus, CAMBER can create a pull or lead in a vehicle. If CAMBER is the same on each side of the vehicle, the pulls will cancel each other, but if different, the vehicle should pull towards the side with the most positive CAMBER.
CAMBER is sometimes used to correct a minor pull problem, especially with front wheel drive vehicles. Due to manufacturer's tolerances on their specifications, some amount of adjustment is permitted. If pulling LEFT, increase right side CAMBER, or decrease left CAMBER. If pulling RIGHT, increase left side CAMBER, or decrease right CAMBER.
-Cross Camber
CROSS CAMBER is the difference between the left and right CAMBER readings. CROSS CAMBER can cause a pull. Often, this can happen even when both CAMBER readings are within specification, particularly if the tolerance (+/-) is large. For this reason, more and more manufacturers are specifying maximum CROSS CAMBER and CROSS CASTER values.
-Toe
TOE settings during driving should be straight ahead. During driving, normal forces may cause the TOE settings to be different than when the vehicle sits on the alignment rack. For this reason, manufacturer's specifications are usually near zero but not at zero. Incorrect TOE settings cause the tire to roll at an angle. This is the leading cause of tire wear!
TOE IN (Front of tires is closer together) is positive.
TOE OUT (rear of tires is closer together) is negative.
TOE should be adjusted after CASTER and CAMBER.
-How Toe Is Diagnosed
Your FMC Visualiner can diagnose and correct TOE problems before tire damage is done **** that was info specifically for alignment machine**** If however, a vehicle has been driven with improper TOE, the wear pattern on the tire will tell the story.
Excessive TOE IN will cause the increased wear on the outside edges, and the tread will often be saw toothed. When rubbing the tire with your hand from the inside towards the outside, the sharp edges will be felt.
Excessive TOE OUT will cause increased wear on the inside edge, and if saw toothed, the effect can be felt by rubbing from the outside to the inside. Badly misadjusted TOE can also cause: wander, poor handling, and a crooked steering wheel.
