Understanding King Pin Inclination (KPI) / Steering Axis Inclination (SAI)

KPI / SAI is the inward tilt of the king pin, or ball-joint / bearing plate - at the top. The KPI / SAI angle and camber are related. The principle purpose of KPI / SAI is for proper component load distribution and to position the tire so that the KPI / SAI and camber meet at a common point where the center of the tire contacts the road.

Most front suspensions carry a king pin / ball joint / bearing plate that is inclined inward at the top.  This angle has the effect of placing the turning point at the center of the tire instead of toward the inside of the wheel. The result is more stable steering.

Combining camber angle and KPI / SAI angles is referred to as included angle. Camber is built into the wheel by forming the spindle with a downward tilt. KPI / SAI angle is built into the end of the axle. While the two angles are interrelated, it is best to measure them separately. (This is necessary in order to determine a bent spindle, king pin or damaged suspension connection components.)

When the KPI / SAI relationship is correct, the weight of the vehicle causes the front wheels to automatically straighten out after a turn. As the wheel turns, the end of the spindle rises and falls. One side of the vehicle is raised as the front wheels are turned to the right or the left and is lowered when the wheels are in the straight ahead position.

Why Measure If You Don't Correct??

Bee Line recognizes that in addition to allowing the measurement of critical alignment angles, it is important that alignment equipment allows you to correct all out of tolerance alignment angles. After all, what good is it knowing the truck is out of alignment if you cannot correct the problems? This means not just correcting toe and/or rear tracking, but also correcting camber and caster. For those who want their truck aligned should expect that the shop can not only measure the alignment angles, but also have the proper equipment to correct any errors found.

With the ability to correct toe, rear tracking, and camber, Bee Line allows you to fix the #1, #2, and # 3 causes of tire wear and increase fuel efficiency. Also, with the ability to easily correct caster, vehicle handling can be improved increasing driver comfort and safety.

The Bee Line Advanced Aligner Runway machine and our alignment tooling is designed to allow a shop to perform all necessary alignment corrections. The machine places the truck at a comfortable working height, either in a pit or above ground. It allows you room to make adjustments to not only toe and tracking, but also camber and caster. It also allows you easy access to the vehicle's front end to inspect for worn front end parts and to perform necessary measurements and corrections. There is no fixed beam or equipment hindering access or making it difficult to work on the vehicle.

Bee Line's patented camber tooling can correct out of tolerance camber on all axle sizes and also correct any axle twist. The floating beam system is designed to be easily attached to the vehicle axle for corrections and removed and placed out of the way when the correction is finished. Special Bee Line fixtures also allow easy removal and replacement of caster wedges.

Bee Line has long been a proponent of the benefits of camber correction. We know that our patented camber correction equipment, along with our many years of experience and extreme accuracy allow users of Bee Line equipment to perform camber correction safely and accurately. Camber correction, as part of a "Total Vehicle Wheel Alignment", allows vehicle owners to achieve maximum tire life and fuel efficiency.