What makes a motorcycle stop, turn and accelerate smoothly and
predictably? It's the geometry. The relationship of rake angle, trail, tire
diameters, swing arm slope, swing arm length, and certain ride heights are what
make a motorcycle handle....or not. Old school thinking related weight bias to
handling, how ever our research has proven that large changes in weight bias
have far less effect on handling then the dramatic changes in geometry that
result in negligible changes in weight bias. Your Computrack measurement will
also log the geometry of your chassis and allow the operator to determine if you
have the optimum geometry for your chassis. Adjusting your geometry for best
performance is called "Optimizing".
When we set up a chassis's geometry we start
at a known good starting point for that model, tire, riding style combination.
After some fine tuning with the rider we arrive at what we call the "Sweet
Numbers". These are your "sweet Numbers" for that model of bike. Now when you
buy another brand or updated model we can set up your new chassis to handle
similar to the old one. Also since tire diameters have a profound effect on
geometry, we can help test and evaluate alternate tire brands or sizes.
Rake Angle: The angle from steering axis to vertical.
Trail: The distance from the steering axis back to the center of
the contact patch measured along the ground.
Wheel Base: Distance from the front axle to the back axle center
Swing Arm Length: Distance from Swing Arm Pivot center to rear
Swing Arm Angle: The angle of the swing arm to the ground. (
note that many swing arms are made asymmetrical, and therefore angle finders are
not able to measure this parameter)
Tire Diameter: Over all tire diameter ( or measure the
circumference and divide by 3.1417)
Here are some changes to ride heights and how they effect
Lower front ride height: Steeper rake angle, less trail, flatter
swing arm angle, shorter wheel base.
Lower rear ride height: Slower rake angle, more trail, flatter
swing arm angle, longer wheel base.
Shorter Swing Arm length (larger sprocket or shorter chain):
Slower rake angle, more trail, steeper swing arm angle, shorter wheel base.