The average sport motorcycle today has adjustments for all sorts of things related to suspension and handling. You can raise or lower ride height at both the front and rear, change compression and rebound damping, swap tires for a different size, profile or stiffness, change the wheels, change springs, get a performance swingarm or new forks and this doesn’t address the truly motivated biker who might buy a whole new frame or even build one himself. What becomes clear after attending Tony Foale’s Motorcycle Handling and Chassis Design seminar is the incredible effect even one small adjustment can have on the overall performance of a motorcycle.
The seminar I attended this week had quite a group, there were folks from Dunlop, Honda and Cannondale, individuals with their own motorcycle related businesses, amateur racers and several others who were just very interested in how a motorcycle really works. After two days, it’s apparent we only scratched the surface and the truth is, there is no way you are going to learn all about how motorcycle suspension works in that amount of time, but you will get exposure to a whole range of things you may not have thought about in great detail.
If you’re curious about the material, here’s an example:
Tire characteristics, suspension and offshoots
· Basic construction.
· Differences between radial and cross ply.
· Why radials have lower profiles
· Some reasons why we need tires.
· Tire is NOT a gas spring. Force/deflection curve is basically linear.
· Suspension action of pneumatic tyre.
· Weight support. – how?.
· Optimum conditions for maximum traction.
· Tire hop and damping.
· Suspension settings and differences between optimum for comfort and performance
· Contact area – variation with load.
· Some geometric effects of tire width.
· Sidebar on basic bike geometry – rake and trail, as a lead-in to:
· Pneumatic trail.
· Mechanisms of tire friction.
· General shape of force vs. slip curve.
· Driving and braking slip.
· Steering slip – slip angle.
· Camber force.
· Concept of steering and camber stiffness.
· Combinations of steering and camber forces.
· Required steering angles at given cornering speeds.
· Friction ellipse.
· Drifting and throttle steering.
· How tire characteristics provide limit feel.
· Variation of grip with vertical load.
· Under/over-steering from tire view point.
· Under/over-steering from steering and stability view point.
And that is just the morning session on day one!
Tony Foale has a long history in the field, having designed and built quite a number of motorcycles himself. His knowledge though, seems to stem from his desire to figure things out on his own. His calculations are based on measurements he took instead of accepting what someone else says. Using his own software he then runs the numbers to find out what the motorcycle does. His class shows the results of that work and though there is a lot of math behind it, you don’t have to delve deeply into trigonometry and calculus yourself to see how things relate. Simulations with his software show how changing one parameter in the suspension changes the reaction of the entire bike.
“The only thing you cannot change is ‘one’ thing” was something Tony said many times and once you see how a small adjustment in something like ride height can drastically change everything else, it might make you a little more thoughtful before casually moving everything around. It makes you cringe when you think about the “design” process followed by the average television motorcycle builder. You’ll also shake your head when you read those magazine road tests where they quickly slide the fork tubes up, raise the rear, change the tires and adjust damping all at once and then go back out to see how it works. … Right.
Of course, many if not most of these changes will only be felt by someone who has a very good feel for the bike in the first place and only in those environments where handling is a consideration. On the track, all of this is important, on the road where you’re not testing the limits of the bike (or shouldn’t be) you’ll less often get into the regions where it makes a huge difference.
If knowing how motorcycles work, if understanding the dynamics of the suspension and how design decisions are made is something you find fascinating, check out one of Tony’s seminars. He doesn’t run them often but they are worth the trip. Your other option is to buy his recently revised book, Motorcycle Handling and Chassis Design which covers essentially the same material as his seminar but in even more detail. He also has a recently revised software package that allows you to enter a multitude of parameters while designing your own suspension and you can see how the motorcycle reacts to each change. Good stuff.
If you’re a casual rider with no deep technical interest, this seminar is not for you but if your toolbox is well used and your knowledge of motorcycles is constantly growing, Tony’s seminars and book are something you’re likely to enjoy.
Link: Tony Foale Seminars