Classic Springer Forks are produced for different frame rakes.

• In the beginning, both the main tubes and the steering stem were in the same plane. This is called "inline". The rake is 0°. Of this type were all 45” Springer forks 1936-1957 and all Big Twin forks 1936-1945.
• From 1946 onwards the Big Twins had the neck angle increased to 30°. To maintain fork inclination and ground clearance, the steering stem was tilted to the rear by 3°. We call these forks Offset -3°, they were stock on 1946-1948 Big Twins.
• When building a bike with ≥+8” extra long forks you don’t want the steering neck so high and inclined that the bike is difficult to steer. Therefore such forks are manufactured with a positive rake, i.e. the steering stem is inclined to the front by 3°. We call these forks Offset +3°.

The sketch shows the placement of the lateral tubes and steering stem seen from the drivers place. Now it is clear, too, why there have to be three different types of top trees or handlebars for Classich Springer forks.