Rear Shock Length (and how it changes the ride)

warp9.9 said:

Ok Rick get the car tire up to speed. Just run it until the speedometer needle points to the oil warning light. Then you are in the warp zone. Bull you have a roadster so your speedo hits a peg.


After that we can work you towards 6 O'clock if you really think that car tire is stable.

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1olbull said:

Imagine your motor sitting upright on your garage floor.
Now imagine you hook a lift to the frame at the top shock mounts.
As you lift the rear up (front wheel remains on the ground) what is happening to the angle of your steering head and front forks? That OEM 32° rake is becoming smaller.
Trail is measured from where a perpendicular line from the axle meets the ground to where a line through the center of the steering head meets the ground.
Shorter the trail, quicker the steering and lees the stability at speed.
Longer the trail, slower the steering and greater the stability at speed.
Trials bikes have less trail for more maneuverability at slow speeds. Ride one over 30 mph and your sphincter will surely pucker! Sport bikes are designed for a combination of handling and speed and will have more trail than the trials bike. Cruisers and Touring bikes will have greater trail for better stability (less demands on control) at highway speeds. They also will be more difficult to control at low speeds where counter steer goes away (parking lot stuff).
Remember that Motorcycless are produced for the lowest common denominator of their purchasing public with liability being a huge factor.
Once we purchase a motor, we are pretty much stuck with its frame geometry. The enthusiast wishing to improve the handling of his motor to best fit his abilities will experiment with rake & trail.
The diagram below is a comparison of the OEM Roadster (red) and how just changing tire sizes can noticeably affect handling. As you can see just a .62" reduction in trail will result in a large difference by quickening the handling.

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