from this article: http://web.archive.org/web/20060717170926/http://www.coe.uncc.edu/~gkwatkin/Dissertation/chapter14.pdf

So: is steering understood?

* Whitt, Frank R.; Jim Papadopoulos (1982). “Chapter 8”. Bicycling Science (Third edition ed.). Massachusetts Institute of Technology.

Dunno, there’s just 1 chapter of a study there. It says the results of previous chapters are that a bike with zero trail is optimum. Maybe lab tests aren’t the best way to design bikes then.

To be honest I haven’t read the article but that was a conclusion that I came across when doing a bit of research into it.

I think the effect of geometry is pretty well understood however the interactions between all variables is hard to quantify at any given moment

It’s surprisingly badly understood, particularly the question of why a bike can be ridden with no hands.

It’s hard to make much sense of the chapter above on its own, and specifically what they were trying to optimise when they concluded that zero trail was “optimum”.

This observation in the second paragraph: “A bicycle with zero mechanical trail clearly cannot be ridden “no hands,”” has been proven to be incorrect:

http://www.youtube.com/watch?v=YdtE3aIUhbU

So I think it’s fair to say that a full understanding of bicycle stability is at best very recent.

The question of what the optimum geometry is for a given application, taking into account factors such as “feel” and human behaviour is more complex again.

The first edition of Bicycling Science has a couple of big impressive formulae modelling bicycle steering. They were dropped from the second edition.

I think the honest answer is that it’s possible to understand the basic steering dynamics – how a riderless bicycle behaves, why if you rotate the forks and give the bike a push it’ll go on for ever, stuff like that. the much more complex interaction of rider, feedback, terrain, traction etc is much, much harder to understand.

The only other observation I’ve made is that every time a so-called unrideable bicycle has been built, someone has eventually learned to ride it.

I think the honest answer is that it’s possible to understand the basic steering dynamics – how a riderless bicycle behaves, why if you rotate the forks and give the bike a push it’ll go on for ever, stuff like that. the much more complex interaction of rider, feedback, terrain, traction etc is much, much harder to understand.

though not if you push it backwards.

Brant> if its a rear wheel steer bike would it roll a good distance if you push backwards?

The model is purely mathematical, and assumes the rider has the instantaneous ability and infinite strength to perform any prescribed corrective action.

At the instant the path of the bicycle diverges, a corrective steer torque is computed and applied by the steering model, with no delay factored in to consider the reaction time of a human rider.

There’s quite a lot of delay caused by human reaction time though, isn’t there? So the model is just wrong.

Thanks to the OP and pdw for the interesting topic and links!
Not all understood but still interesting.

Cheers!

There’s also the effect of over correction. An effect I saw to hilarious results many years ago when a mate’s stem came loose up Glen Tilt, and we bodged the stem to the forks with a bungee cord. In a straight line he was fine, in corners it was amusingly uncontrollable 🙂