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TIRE SQUEAL When Turning - SR-115

The Ackerman steering geometry on most production cars is not perfectly aligned with large steering angles. The inside front wheel needs to steer farther than the outside one to track (orbit) around the same center of rotation in the turn. Ideally the axis of the front wheel spindles should intersect on the rear axle line. Quite often with a tight turn the outside front tire will turn too far, or the inside front tire does not turn enough (all relative). Then one of the front tires has to skid sideways a bit during a tight turn. This is equivalent to having toe-in severely misaligned when driving in a straight line.

Older tires are more likely to squeal than new ones. Brand new tires may squeal during the first five minutes of use until the mold release compound is worn away. Freshly sealed asphalt pavement has poor grip and is likely to make tires squeal. Lots of cars will make front tires squeal on full steering lock, perhaps more likely when backing up.

Slip angle of the tires enters into this issue when turning at higher road speeds. In this case the center of orbit for steering moves forward for the rear axle line, and the steering geometry wants to be different. For high speed competition you would want the steering geometry optimized for best performance in high speed turns. For lower speed competition (autocross), you might want the steering geometry optimized for best turn in at moderate speeds. For normal road touring the steering geometry (as on production cars) should be optimized for smaller steering angles and modedrate speeds, such as 45 mph on an experessway exit ramp.

You can find an extensive article on steering setup at  www.smithees-racetech.com.au.

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