Checking the Steering Axis Inclination Angle

Steering axis inclination angle is also known as the kingpin inclination angle. It is the angle that the spindle is in relation with an imaginary line drawn between the upper and lower balljoints. A steering inclination angle of 0 deg indicates that the spindle is at 90 degrees to the imaginary line. Most cars are set for 6-10 degrees. This is designed into the spindle and upright and cannot be adjusted. I designed in 7 degrees of steering axis inclination and was pleasantly surpised to see that it measured exactly 7 degrees.

caster/camber gauge

Steering axis inclination measured on gauge 90 degrees to rim and inside blue scale.

To measure steering axis inclination, the method is identical to caster measurement except that you use the steering axis inclination guage which is at a 90 deg angle to the caster gauge. The wheel is turned 20 deg inward. The steering axis inclination gauge is centered for 0 deg caster. There is an adjustment screw on the back of the gauge that allows you to set it for 0 deg. The wheel is then turned to 20 deg outward for a total movement of 40 degrees. The steering axis inclination angle is read off the gauge.

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Copyright March 2011 Eugene Blanchard