Tire Book Errata
I regret these errors but I'm also pleased there weren't more
Fig. 6.19, Incorrect
Fig. 6.19, Revised
In the original figure I made the mistake of drawing the drag
vector opposite in direction to the tire heading. It should be
in the opposite direction to the vehicle heading, it's a drag
on the car. The explanation is correct but I should have included
the point that Fcentripetal can't be bigger than the Flateral
as it is in the original drawing. The tire can't generate a force
on the car larger than its own lateral force.
The man who pointed out this error is Dr. Allen E. Fuhs, a
Distinguished Professor Emeritus and SAE Fellow.
I thank Dr. Fuhs for caring enough about the subject to read
the material carefully and to point out the error.
"Percent anti-dive" should be Percent anti-squat.
At the bottom of the page. In both these expressions I left
out the notation that includes dividing by the track. The calculations
on the next page using these expressions are correct.
"The rear roll force weight transfer fraction is A x
(CG - RC) x (RM/TM) / front track."
"The front roll force weight transfer fraction is A x (CG
- RC) x (FM/TM) / rear track."
Under the Roll Angle heading, the first sentence reads: "The
roll angle of the car depends on the roll moment and the roll
resistance of the springs, anti-roll bars, and dampers."
I should not have included dampers in this sentence.
The roll moment causes chassis roll until the roll resistance
of the springs and anti-roll bars builds up to equal the role
moment. When roll resistance equals the roll moment, roll stops.
Dampers add roll resistance only when there is some movement
of the shaft/piston in the damper. Just before roll begins
there is no damper force because the damper shaft/piston is not
moving. When roll stops there is no damper force for the same
reason. So it's springs and bars alone that determine roll angle.
Damper forces influence the time it takes for spring and bar
forces to build up and they also influence tire contact-patch
forces during roll, but they do not influence final contact-patch
Under the Caster heading I got mixed up on one sentence
but the rest of the explanation is correct. The third sentence
in the first paragraph should read:
"If caster is symmetrical, the same on both wheels, steering
to the left lowers the left wheel vs. the chassis and
raises the right.
Under the Roll Resistance Distribution heading, first
sentence in the third paragraph: ABR should be ARB. This
is, of course, an abbreviation for Anti-Roll Bar.
I'll add more errata as I become aware of them.