Toe-- from a viewpoint above a car, toe is the angle of a wheel indicated when the front of the wheel is pointed more inward or outward than the rear of the wheel. When the front wheel is angled more towards the center of the car than the rear of the wheel, the wheel has toe-in. When the front of the wheel is angled away from the center of the car more than the rear of the wheel, the wheel has toe-out. Toe-in increases straight line stability. Toe-out increases response to steering inputs, but can cause a car to be unstable when driven across road surface imperfections.
For the track, the front wheels of both front and rear wheel drive cars prefer toe-out to provide better response to initial turn-in typically in the range of 1/8" to 1/4" total toe out (i.e. half of that for each wheel). A FWD car may need even more toe-out on tight road courses and autocross on the order of 1/2", but this will cause excessive drag and sacrifice speed on faster courses, and cause excessive wear on the street in addition to being very difficult to keep in a straight line.
For rear wheels on independent suspensions, toe-in is necessary to provide straight line and cornering stability. Toe-out on the rear wheels is never used. Solid axle cars should have a toe of zero (or something is bent).
Below is a list of automotive and road racing terms. Click on any of the letters to go to the start of that section, click on the term to open a window with the definition.
aerodynamic
anti-roll bar
apex
aspect ratio
backmarker
balaclava
balance, handling
bedding pads
blip, throttle
blocking
blow-off valve
brake bias
braking point
brake-turning
breathing the throttle
bump steer
camber
camber, negative
camber, positive
castor
chicane
chief steward
contact patch, tire
corner apex
corner entry
corner exit
corner station
corner turn-in
corner worker
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tactile feedback
tight (handling)
trail braking
toe
turn-in point
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terms coming soon