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Most people who racers on pavement do complete all of their braking
before entering a turn. They accelerate out of the corner after the
apex, when they are no longer using all of their traction to corner.
Some people do late or early apexing so that they can trade off
between a faster speed through the corner, and longer time to
accelerate out of the corner, but they still do not accelerate before
the apex or brake after they turn the wheel. I studied this subject
quite a bit years ago when I began studying physics, and what I
learned about friction and vector addition didn't coincide with the
"common knowledge" among people who race cars. I don't claim to know
everything about this subject, but I argued from the same position
that you are before I dug deeper.
Your vector addition is correct, but you cannot simply add vectors
and say that the tires can handle 1G in any direction, because there
are many variables affecting the system. For one, the weight
distribution shifts when you begin to turn the car, which results in
significantly more weight on one side of the car, and changes the
angle of the tires relative to the road somewhat. Both of these
effects cause the weight of the car to be spread over a smaller tire
surface area. Friction is independent of surface area, but most of
the force that holds a car on the road is not technically friction,
but a mechanical interlocking of the road surface with the rubber in
the tire. The rubber actually shears when the tires slide, and if the
weight is spread out over a larger contact patch, it will take more
force to shear. This is how race cars can corner at greater than 1G,
when friction over 1G is not possible. When turning, the overall
traction of your tires is significantly reduced.
Tyler
On Dec 5, 2006, at 6:08 PM, Mitch Haley wrote:
I disagree. If you were correct, racers would never brake into
or accelerate out of corners, they'd do all their braking and
accelerating in a straight line before and after the corner.
Let's assume your tires can handle 1G in either cornering or braking.
You can brake at 1G, corner at 1G, or do both at once at the
square root of 1/2 or 0.7G in each direction.
Mitch.
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