Handling Qualities for Bikes and Recumbents


A:- I would recommend 1/2" to 3/4".  Less if you have little or no tiller in the steering.
One thing you have to do when converting a motorcycle for sidecar use is to reduce trail to about 1/3 to 1/2 of the trail it had when it was a leaner. I have ridden motorcycles with sidecars where this hadn't been done, and the result was horrid.  So much effort was needed on the (wide) bars that you could actually see the forks twist.
Trail doesn't make the front wheel go straight anyway.  It allows the wheel to be steered by sideloads.  On a wedgie this allows the bike to be steered while riding "no hands" by applying side forces to the pedals.   (This has been known for over a century, it's spelled out in Sharp's book). Hard to do on a recumbent, but SWBs with large amounts of trail suffer from pedal steer.
BTW I am careful about steering ergonomics of my 2 wheel recumbents, so most people who have ridden them think they handle great.   Yet none of them have more than 1/2" of trail, some have almost none.
Mark E. Stonich   Minneapolis, Minnesota Human Powered Vehicle Assn.

  1. Draw a line on a piece of paper. This is the road .
  2. Draw your wheel on top.
  3. Pick a point about 1.5" infront of the contact point, this will be center of pivot.
  4. Figure out where you want your hands.
  5. Put a mark between 4 and 8" in front of your hands. This is the tiller. 4" will feel quick to the point of being squirrely 8" will feelheavy and a lot more stable. If you decide on less than 4" many people will feel unsafe on it, I know because i have one.
  6. Draw a line from the spot from #5 to the center of pivot from #3. This is the line you should place your head tube on.
  7. Measure from the head tube line to the center of the wheel and you will have the rake needed for your fork.

I didn't believe this when I first had it explained to me, but recently I broke the handle bar on my SWB. when I repaired it I wound up with more tiller in than I had before, and the bike went from being difficult to ride to almost normal. I went from 0" of tiller to 1" of tiller and it made a huge difference. Before to get the bike rideable I had about 4" of trail with the forks almost straight. I really should put more tiller into the handle bar to get it closer to 2.5"
That is the little bit that I know about front ends, thankfully it works whenever I need to design anything, so I don't really work on design past using this method.


Thursday, 29 January 2009