Quote:
Originally Posted by drmiller100
The front wheel on a bike is pretty interesting. The caster is actually determined by the angle of the steering head.
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By convention, rake is determined by steering head angle. Caster (usually called trail in motorcycles) can exist at any steering head angle. It is partly controlled by rake, but also controlled by offsets of the axle on the sliders, and the triple clamps.
You can have a bike with a vertical steering head but with as much trail as you want.
I think your summary of effects is pretty good, although the effects are so intertwined (and affected by other things, such as frame stability, masses that move with the handlebars, etc.) that it is hard to make generalizations.
Many bikes are effectively spaghetti... we use to straighten out front ends after a fall, by holding the front wheels between knees, and twisting the handlebars. When I was an inspection mechanic, I was tempted to flunk any chopper that came into the shop: they had nothing that could be called "handling," and nothing that could be called "brakes". One season, I rode a 250cc single in the 125cc GP class, and it handled perfectly, in my view. But when pulling into the pits once, I sat up, raised my hand to signal, and the bike went into tank slappers. (This with a pretty stiff frame, very stiff forks, and geometry that was very ordinary for a road racing bike.) The front brake was large relative to the bike's weight, so I suspect this had an influence.
As far as I know, it's all magic.
Tony Foale has done some cool experiments with rake and trail... and lived to tell about it. (Darn frames... this link came from the article itself, but only gives the base address. If you look under "articles" you'll find the rake and trail one, where he describes modifying a BMW in pretty dramatic ways.)