This unique handbook assumes no starting knowledge of vehicle aerodynamics. It begins with simple ideas and finishes with sophisticated and effective aerodynamic modifications that work. Three major chapters cover on-road testing techniques that give you all the information you need to decide what modifications you should make - and, after you've made them, how well they work. Low-cost techniques allow you to visualise the patterns of airflow over your car so that you can actually see the problem areas that need improvement. Uniquely, you're also shown how to measure aerodynamic pressures, so you can determine which body surfaces are creating lift, drag and downforce. Want to work out where a wing should be placed? On-road testing to find that out is covered as well. The book also shows you how to measure downforce to see if that wing is actually working! If you wish to reduce drag, more than ten different areas are covered. Reducing frontal area, lowering cooling system drag, optimising vehicle ride height and rake, reducing the strength of the wake, achieving clean airflow separation and optimising wheel designs - they're all covered using the latest research findings. And if you're a performance driver, there's a major chapter devoted to reducing lift and improving stability. This chapter includes the design and development of undertrays and diffusers, wings and spoilers. The example car developed measurable downforce when fitted with an undertray and rear diffuser, something that transformed its on-road handling. The author has been writing about the aerodynamics of road cars for more than 25 years. He is also an experienced and proficient car modifier who has performed numerous aerodynamic modifications and upgrades to his own cars. The book's technical consultant, RH Barnard, is an acknowledged world leading automotive aerodynamicist. If you want a practical, hands-on guide that demystifies and explains car aerodynamics, and shows you how to make effective aerodynamic modifications to your car, this book is for you.