Handling is
anything we can do to make our Driver/Race Car combination faster, through chassis
and suspension development. The techniques and ideas we can use apply in all forms
of racing - circuit, speedway, offroad and rallying, even though the requirements of car
performance will be different.If
you are building a street car, or performance road car, you will also be interested in
improving
handling.
For our purposes in this series of
articles, we will equate "handling", with the "chassis and suspension
set up".
Consider the following list of chassis set
up items that could influence handling:-
Tyres - tyre and wheel width,
construction, compound, temperatures, pressures
Chassis and suspension component stiffness
Suspension motion - sufficient bump and rebound travel? any friction, jamming?
Weight of the race car, unsprung weight
Wheel base and track
Centre of gravity - location
Roll centres - front, rear, roll axis, movement of the roll centre as suspension bumps
& rebounds
Ride height
Static corner weights
Springs, anti-roll bars, shock absorbers - control tyre contact with the road, roll
stiffness, pitch
stiffness, weight transfer, grip and balance, drivability
Camber curves, static camber
Anti or Pro dive and/or squat, zero droop front suspension
Roll steer, torque steer, live rear axle driveline torque effects, braking/accelerating
torque affects.
Tyre scrub - track variation due to suspension geometry.
Steering related geometry - bump steer, toe, castor, camber, SAI, scrub radius, Ackerman
Differential - open, locker, limited slip
Aerodynamic
downforce
This is by no means a complete list, and
does no justice to the relative importance of the various
items. It serves only to indicate the areas we might consider in tuning the
suspension on the race
car. A minimalist approach for a car with limited adjustments might be to calculate
overall
roll resistance required, specify suitable springs, anti-roll bars and shocks, do a
complete
workshop set up, and go testing. From there on, and with cars of increasing
complexity, who knows
exactly where the extra car speed will come from? It requires knowledge, an
enquiring mind, and
the resources to test.
Of all the theory that might be implicit
in the above list, the most important for the Race Driver
and Engineer/Mechanic is weight transfer. It lies at the heart of their endless
quest for grip and
balance. Therefore I have chosen to deal with it in some detail.
You won't read stuff exactly like this
anywhere else. I draw heavily on the work of Mark Oritz, writing in "Race Car
Engineering" magazine. From my own experience as a driver (many years ago), and
suspension tuner, I have attempted to generalise his work, and make it more usefull for
track tuning.
GO TO "DYNAMIC LOAD TRANSFER"