Kingpin InclinationKingpin inclination angle is the angle measured from vertical to an imaginary line drawn through the center of the upper and lower ball joints on an IFS system. By offsetting the ball joints, a vertical arc is produced as the wheels turn. This angle, coupled with correct scrub radius, has a direct bearing on how easy it is to steer the car and its responsiveness to steering corrections.

Scrub RadiusIf the KPI is correct, the line drawn through the ball joints, or through the kingpin on a straight-axle car, will meet the centerline of the front tire where it meets the road, or just slightly to the outside of the centerline. The distance from the tire center to the kingpin inclination angle contact point on the road is called the scrub radius. Changes to wheel height and offset will affect the scrub radius, and can lead to prematurely worn tires, bearings, and steering components.

Four-Wheel AlignmentSo now that you know how to build correct suspension geometry into your next project, what do you do when it comes to setting the alignment perfectly? For total peace of mind and a rod or custom that will take you safely wherever you choose to drive, a visit to your local alignment shop should be on your schedule. Not only will they adjust and set your frontend alignment, they'll be able to measure and set the alignment on all four wheels. We haven't touched on it here, but the rearend can affect handling too, and not just by being mounted out of square in the chassis.

SOURCE
Art Morrison Ent.
5301 8th St. East
Fife
WA  98424
www.artmorrison.com
Kiwi Steve's Hot Rod Shop
www.kiwisteves.com
Chassis Engineering
P.O. Box 70
West Branch
IA  52358
3-19/-643-2645
Magnum Axle
Classic Performance Products
175 East Freedom Avenue
Anaheim
CA  92801
800-522-5004
www.classicperform.com
Posies
717-566-3340
www.posiesrodandcustom.com
Fatman Fabrications
704-545-0369
www.fatmanfab.com
Rodparts Warehouse
Heidt's Hot Rod Shop
111 Kerry Ln.
Wauconda
IL  60084
8-00/-841-8188
www.heidts.com
Speedway Motors
P.O. Box 81906
Lincoln
NE  68501
4-02/-474-4414
Jim Weimer Rod Garage Unisteer Performance Products
www.unisteer.com
JPL Street Rods Walton Fabrication
1933 W. 11th St., Ste. H Dept. CRM
Upland
CA  91786