Positive Vs: 0 Scrub

To be truthful, I don't know why they designed the 0 scrub, 0 kingpin. I can understand the need to reduce the steering axis inclination in order to reduce the camber change of the outside tire during sharp cornering, however, most tracks have fairly large radii turns and the ackerman steering angle would be under 3 or 4 degrees almost all the time. 

The steering axis inclination does contribute to the forces and moments in the steering system, so, on high down-force cars without power steering, reducing the inclination will lighten the load at the steering wheel. This parameter also provides a self centering effect in the steering which is considered to aid in controllability or stability. As such I always recommend using some inclination but never zero.

Scrub radius is a function of the steering axis and the wheel position. They may have used no inclination to achieve the zero scrub radius. Again, on the zero scrub radius I don't understand the thinking. Zero scrub radius (a.k.a. center point steering) is common on front wheel drive cars because without it, if one tire loses traction it is possible (under full power conditions) that the steering wheel can be yanked right out of your 
hand. However, on a race car, a positive scrub radius provides feedback to the driver. If one tire loses traction (or both tires suddenly drop grip e.g. on oil or water) there will be a change in the feel of the steering. Ever noticed how "light" the steering feels when you run on ice in the winter? On the other hand you don't want and unbalanced scrub radius (side to side) or a hugely large scrub radius, but I always recommend some positive scrub radius for the feel. Why they used 0 I don't know. 

Keep in mind you configuration could be an unfinished experiment. Too many designs end up in production because time ran out. 

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Last modified: June 21, 2011

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