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"Every Racer's Guide to Suspension Tuning"
 Recommended for every one interested in handling, especially for racing and high performance
 
Dale Thompson, December 2015, www.suspensionsetup.info

 

A Series of Articles on Race Car Chassis & Supension Set Up.  (All of the following is superceded)

Grip? Balance? Transient Behaviour?....
("transient behaviour" might also be considered as "handling balance variation")

These are the big three questions we will attempt to unravel in this series of articles.

Race Drivers:  Learn about the responses of your race car - what you are doing to it, and what it is doing to you - so you can focus your efforts in areas bringing greatest improvement.  If you were a young driver, testing for a V8 SuperCar drive, this is the stuff you would be expected to know.  You should be able to work with the team to balance the car.

Race Engineers/Mechanics and Drivers Responsible for their Own Set-Up:
Develop a model that will help you address the grip vs balance questions, as you look for improvements in the race car set up.

It is generally accepted that feedback from the driver is the most important input for tuning the race car balance - the driver can feel very small changes in balance.   However, the driver will not be as sensitive to small changes in overall grip.   Therefore, improvements in overall grip may come from any of a multitude of analyses and or data sources.

Read a synopsis here.   (Summary of the ideas presented in the articles.)
Read "A Mindset for Analysing Suspension Set Up Problems".

     Introduction

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. 

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