What actually makes a bike turn?

[TKW]

Steering vs leaning, and interesting study.
http://www.popularmechanics.com/automot ... 68501.html

Almost since the time motorcycles were first made, enthusiasts have pondered the question--what action actually turns a motorcycle? Some say it's leaning your body, while others contend it's turning the handlebars. Finally, someone has a definitive answer:

This long-debated topic is a serious matter, says a recent article in Popular Mechanics. Investigations that reconstruct accidents found that in incidents involving obstacles, most riders do not even try to steer away--an action that could have been life-saving. According to the article, this is largely because many riders are getting downright contradictory information about their bike's steering function and are thus more likely to get confused and panic in emergency situations.

Keith Code, a prominent motorcycle riding instructor and founder of the well-regarded California Superbike School, has finally provided a clear answer to his long-debated question. He recently built a No Body Steering Bike (No B.S. Bike) which shows that only steering (yup, steering, NOT body steering or leaning) actually causes a motorcycle to turn.

Code first delved into the basics of counter steering, studying a wide range of material from the Wright brothers' work on counter steering and tandem-wheel vehicles to studies conducted by Honda Motor Co. in the 1970s. He then built the No B.S. Bike based on the midsize ZX 6R Kawasaki. He firmly affixed an extra set of handlebars to the frame above the standard bars. Then he mounted a second, working throttle to the extra bar assembly, thereby enabling riders to keep speed constant while holding the bars.

Every single one of the more than 100 riders who have tried their body steering or leaning methods on the bike have reached the same undeniable conclusion--body steering/leaning does NOT turn a motorcycle. To steer a bike, you actually have to steer it.

[Mag7C]

I tend not to trust studies, so when I first read the article I tried it myself on a straight road. Let go of the bars and lean. You'll drift whichever direction you're leaning, which could be a turn if the curve is really really slow. But the only way I've found to actually make a practical turn is with the bars.

I don't know a whole lot about how leaning your body out while taking a sharp turn works, other than it does, so hopefully some of our more knowledgable members could input on that.

[shane-o]

neva had a problem with steering

but i will say

have ya eva had a passenger who refused to lean with the bike ??? wat happened ?? simple the bike will refuse to committ to the turn.

sure leaning alone wont turn a bike... but I would love to see the average punter throw their bike into a nice juicy set of twisties without leaning with the turn.

ya cant have one without the other.

unless ya wanna see what ya ride looks like surfing down the road, and testing out ya new textiles on the black stuff.

[TKW]

yeah I always kinda assumed it's a bit of both

[Skier]

neva had a problem with steering

but i will say

have ya eva had a passenger who refused to lean with the bike ??? wat happened ?? simple the bike will refuse to committ to the turn.

sure leaning alone wont turn a bike... but I would love to see the average punter throw their bike into a nice juicy set of twisties without leaning with the turn.

ya cant have one without the other.

unless ya wanna see what ya ride looks like surfing down the road, and testing out ya new textiles on the black stuff.

You can simulate a non-leaning passenger by standing on the outside peg of your bike in a turn. Just like slow-speed manuevers, the bike will be hesitant to turn against where the weight is, but believe me, it will turn if you give enough input at the bars.

I've never had a problem with a passenger leaning or not leaning that couldn't be fixed with liberal application of countersteering.

[Sev]

Turning the bars causes the bike to upset the centrifical force of the wheels. Which causes it to start falling to either side. This is your lean.

Now leaning from side to side on the bike will cause you to turn, because you're moving weight onto the inside of the tire which means that the weight is moving towards the inside of the turn and as the contact patch rolls across the surface of the tire you turn.

The handlebars are a way of expiditing this, they cause lean when you turn. This is demonstrated pretty clearly when you stand beside your bike and twist the wheel back and forth, see how the bike leans against the turn?

Anyways handlebars are just leverage to create a lean. The further you push them out the further you lean and the further you lean the faster you turn.

[shane-o]

neva had a problem with steering

but i will say

have ya eva had a passenger who refused to lean with the bike ??? wat happened ?? simple the bike will refuse to committ to the turn.

sure leaning alone wont turn a bike... but I would love to see the average punter throw their bike into a nice juicy set of twisties without leaning with the turn.

ya cant have one without the other.

unless ya wanna see what ya ride looks like surfing down the road, and testing out ya new textiles on the black stuff.

You can simulate a non-leaning passenger by standing on the outside peg of your bike in a turn. Just like slow-speed manuevers, the bike will be hesitant to turn against where the weight is, but believe me, it will turn if you give enough input at the bars.

I've never had a problem with a passenger leaning or not leaning that couldn't be fixed with liberal application of countersteering.

sure, agreed.

think i just picked a bad example of turning with one of the 2 factors removed.

[niterider]

I've read on those be a better riding info that if one turns the front wheel into the object to be avoided, the bike will lean to the opposit side therefore avoiding the object posing the danger. This action has to be practiced in order not to put the rider in danger.

[shawnhpi]

ME!

[blair]

During my warm-down after my bicycle ride this morning I was playing with lean and angles and turns and stuff.

As usual, I'm totally convinced that gyroscopic motion has nothing to do with it.

In order to maintain a steady-state turn over a line of contact, the center of mass has to be to the inside of the turn, and the rate of turn must be accelerating the center of mass to the inside. If the rate of turn is too small, the center of mass will drop; if it is too great, the center of mass will be lifted.

Counter-steer is part of turns at speed, but I was doing some low-speed turns after leaning the bike to the side and keeping my line straight, and the action is weird.

I can maintain the line by keeping the wheels in-line, which requires balancing my center of mass over the pavement-contact line and maintaining a torque on the bars.

The trail of the fork makes the front wheel want to turn into a lean in that situation. When you release the torque, the fork can turn and the bike starts to follow a curve. But I was having trouble detecting either the weight shift or the counter-steer in that situation. The counter-steer might not be there, but the weight shift has to be, just to get to a steady state for the turn. I may be so used to turning on a bicycle that I don't feel those things for what they are any more.

So I think Sev has a little of it right when he says lean is key (the rest of his post made my teeth hurt a little, so I won't go there). Once you're leaning, there's a torque on the fork that induces a dihedral angle which forces the bike to want to go somewhere other than straight.

The reason the "no-BS" bike doesn't turn is that once you're leaning on a motorcycle you have to stabilize the turn with a torque input from your hands, otherwise the fork will turn too far and the bike will right itself again. They're actually turning, but unless they keep increasing the lean, or keep leaning, recovering, and leaning again, the bike will straighten.

I've seen the film of this thing in action, and the difference between the two kinds of steering is obvious. But I wonder if they do the lean-only situation, and hold the body lean, would the bike come back to a lean the other way, which would force a dihedral opposite the body lean...there could be a stable point there with the bike actually turning away from the body lean...

Okay. That's it. The link that started this thread has told us nothing.