I have always admired the more beautiful rake of the Spyder against that of the Bobber and the thought of modifying the bobber did cross my mind so sought advice on the Internet but when I got this reply, I changed my mind:
1. 'Rake' is the angle at which the headstock of the motorcycle is inclined when compared against a vertical line drawn perpendicular to the ground. The rake angle effects steering ability, the smaller the rake angle then the easier the bike is to corner but will be less stable in a straight line.
2. 'Trail' is the distance on the ground between a straight line drawn through the center of the front wheel spindle and a line drawn through the center of the headstock axis. The greater the trail distance, then the greater the straight line stability but the harder it is to make the bike corner.
3. Motorcycle 'offset' is the distance between a line drawn through the centre of the steering stem/headstock axis and the centre line of the front fork tubes. Typically, the offset inversely affects trail, if offset increases then the trail will decrease.
- Increase rake, trail increases;
- Increase trail, rake increases;
- Increase offset for both yokes, trail decreases;
- Increase offset for only top yoke/triple tree, trail increase;
- Increase offset for bottom yoke/triple tree, trail decrease.
No wonder the 34 degree rake commonly found in the Bobber is a good compromise between manuerabilty at low speed plus stability at high speed.