SPORTBIKE SUSPENSION TUNING
by Al
(by Andrew Trevitt, actually, but reviewed by Al)
 |
|
|
Andrew Trevitt was a road racer, and is currently the senior editor of Sports Rider magazine. He's written a book called Sportbike Suspension Tuning.
After three chapters of basic theory (springs, damping, rake, trail, geometry) Trevitt gets into the nitty gritty of changing how your bike handles.
There's a whole chapter on ride height. Trevitt says riders misinterpret the results of suspension changes, because practically every change you make will affect steering in some way. Changing front and rear ride heights affects trail, for example. And sometimes riders make changes unintentionally. For instance, merely adjusting the chain tension on a machine with an eccentric axle clamp will change the ride height, the rake, the trail and the wheelbase of the motorcycle.
There's a whole chapter on springs, preload and sag, another on damping, and one on squat and anti-squat. This last one is interesting. The GSX-R1000 has eccentric swingarm pivots, and changing these can change not only ride height, rake, trail and wheelbase, but also rear wheel squat characteristics. As can changing front sprocket size on most motorcycles.
There's a chapter on tyres, too. Some bikes come with an OEM variant of a tyre -- for instance, Buells come with Pirelli Diablo Ts, which are different from standard Diablos. Trevitt explains why, and he has some considered advice on tyres: establish a preference (your personal compromise on grip/ride/price/longevity) and stick to it, because every time you change tyre brands your optimal suspension settings move. But if you must change, he provides procedures and formulae to adjust the ride height to account for differences in tyre circumference.
Trevitt goes on to discuss finding a setup with stock components, and small cheap changes like springs, fork oil height and fork oil before moving on to aftermarket upgrades.
The final chapter is a troubleshooting guide with scenarios (entering a corner, midcorner, exiting a corner etc), symptoms (chassis resists leaning while trail braking, for example), the likely cause and a possible remedy.
Sportbikes handle pretty well these days, but they're set up for a rider of a certain weight and with a certain riding style. Your weight and style are almost guaranteed to differ from that of the average rider the factory had in mind.
Spending $24.95 on Sportbike Suspension Tuning and following its setup advice may well be the cheapest and most effective modification you will ever make to the handling of your motorcycle.
Wherever good books are sold.
