Sorry, man, but I don't understand the question. I've never heard of the 'caster effect', unless you're referring to the tendency of a castor (wheel) to align itself with the direction of travel. That is based upon the centre of thrust being offset from the axle of the wheel.
Caster effect occurs when the point of contact is offset from the pivot axis, like a wheel on a shopping cart. The wheel will align itself to the direction of travel, because if it's sideways, there's a torque force created that straigthens out the wheel.
In the case of motorcycles, the distance between the contact point and where the axis would intersect the pavement is called "trail".
My dictionaries (Cambridge, and Collins (and also, Dictionary.com!)) give either spelling as valid (when dealing with small wheels, or the effect in question). I was just suggesting trying a different spelling for searching purposes!
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