Demon Bike Bits

The basic frame-up explained
by Michael Scott (SuperBike) 1984

Written by doyen of bike hacks Vic Willoughby, and innovative researcher/designer/builder Tony Foale, the book's chief strength lies in keeping its readers' feet firmly on the ground, while taking them up step by step to lofty realms of mechanics and dynamics. Thus first principles are fully and lucidly explored. For example, why does a motorcycle balance? The answer is that it doesn't really. Rather, it stays on its wheels because it keeps over-balancing, whereupon the combined forces of gyroscopic precession on the wheels and the geometry of the steering lift it up again, Smooth progress is in fact a continuous process of deviation and correction. It goes on to explain a fascinating fact. Since the forces of steering geometry interact with the road through the tyre, the responses of a particular tyre play a big part in the equation. Now, on a wet road, a tyre has less grip than on a dry surface. It's responses are changed, and so are the factors it feeds into the steering equation. And that is why straight-line steering feels lighter in the wet. (One need hardly add that this "feel" is a vital tool in warning us of changes in surface, and is just one of many subtle signals that we learn to use instinctively without ever understanding them).
In clear language, the authors deal body blows to a few sacred cows. The most contentious point concerning rake angle is explored in detail following a series of practical experiments in rake and offset by Tony Foale, a fascinating field of research that I hope to return to at length in the future.
As well as basic principles, the book describes and analyses different materials and types of frame construction, suspension designs both ancient and modern, and takes you as far as you want to go into the mathematics of the matters. Illustration by photographs and simple diagrams makes it all easy to follow, and one emerges at the end with a much clearer view of the simple complexities of motorcycle steering and behaviour. Indeed, for those who wish to go further, there's a chapter as a quick primer in practical frame building, showing you how to cope with the distortion caused by welds as they cool, and such esoteric problems. One of the book's great strengths is that Tony Foale has made many different types of frames and suspensions ... some for experiments, others to race, and still more as a way of making a living. Not only does this add authority to his text, but it gives the book a rich vein of source material both photographic and practical from which to draw.

The Foale-Willoughby book, published by Osprey, stands alone. It has no rivals nobody's ever tackled the topic before. As a result, apart from being very good, it's also the best in the world.