I was thinking, uh, oh!

[Mike Muz]

Fork rake, or is it trail?

Either way, I was looking down at the front end as I was grovelling along and I started to wonder to myself, why isn't the axle to top of headtube a straight line? By this, i mean the headtube and forks in a straight line,
Why are the forks offset? Could it be shock absorption, or would the steering be so slow to operate effetively? Has it been done?

Mike

 

[danson67]

If the forks were straight, ie: zero rake, but still have the same (72ºish) head angle, the fork would have a huge positive trail.
Normal range would be 40-55mm, rather than over 120mm.
This would make the steering very heavy with a lot of wheel flop.

It is possible to have a bike with a straight fork, (see bicycle gymnastics) but these are very special bikes for very controlled conditions and use.
They have the same handling characteristic whichever way around the bars are, but note the steep steering angle to keep the trail within the sensible range:

Have a fiddle with a Trail Calculator, and you'll see that a zero rake fork with the same head angle will roughly double the wheel flop and triple the trail.

All the best,