Originally Posted by
Me a few years ago somewhere else
A buggy in front of Walmart has "casters" on the front, the wheel will turn. You'll notice that the wheel touches pavement behind the pivot of steering axis (an imaginary line drawn through the steering stem or pivot that continues to road or other surface). These casters have a lot of trail, which is why they will readily follow where the buggy wants to go. You don't steer the buggy by turning the casters, you steer it by applying pressure on the handle at back and as you know, they like to go down hill, not across hills or grade.
A motorcycle has this trail built in too, it works better for steering a bike with handle bars attached to the caster because a bike leans when it steers. Even then, trail, or more of it, slows steering response too, but it makes a bike easy to handle, if left as a bike.
When converted to a trike, now we are back like the buggy, we don't lean. We are however attempting to steer it with handlebars connected to the casters. As a caster, it likes to follow, not lead. Trikes do not lean, one does not countersteer to steer it. Lots of trail means a trike will want to always fall off to the crown of the roadway, it means that while you steer left in that left hand sweeper, centrepidal force tries to steer that same front caster straight off the road.
Grandpa's tractor was a "G" model John Deere, it had tricycle style wheel placement. It was much like our trikes with one exception, it had "0" (zero) trail. You look at it and the steering stem axis hits the road exactly where the front wheel does. No lead, no trail. It would go in a circle all day if you take your hands off the wheel after turning it, likewise, it was very easy for this fellow as an 8 year old to steer on the roughest farm road or across grandpa's corn or tobacco field with plows.
Stock, our Gold Wings have near 4.5 to 5 inches trail, the wheel touches the road that far behind the steering stem axis. The front fork tubes and steering stem are right about 30 degrees from verticle.
A rake kit adds 4.5 or 6 degrees to that through offset machining of the triple trees, so that instead of the steering stem and tubes being parallel, the tubes are 4.5 or 6 degrees skewed forwards. This additional rake swings the tubes forwards toward the front, towards the steering stem axis, and it reduces trail to nearer 2 - 2.5 inches, still leaving some trail.
This swinging of the tubes in an arc also will lower the front of the trike as they are swinging through an arc from 30 degrees to more like 34.5 or 36 degrees from verticle. This is why Champion includes fork extensions (they did with my 6 degree kit in 2004), why CSC includes longer tubes, and why Bud Redmon had custom extensions machined for his 1200 trike.
You do not want "0" trail, you want the front to want to straighten up somewhat, you just want to lessen effort required to point it the way you want it to go.
You do not want it to go past "0" trail and into a lead condition, as then the front wheel will want to either fall off to left or right side full lock .... just like your trike does now if you let it roll backwards with any speed. Very dangerous at 50+ mph.
All trike kits for the Gold Wing will derive the same benifit from a rake kit, a lighter steering effort and greater control of where the trike goes under road conditions, acceleration and cornering.