Motorcycle Cornering: Forces Acting on a Stable Bike

  • Thread starter Adrian Baker
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In summary, when turning a corner on a motorcycle, the front wheel has little (no?) effect on the stability. The forces acting on the motorcycle are pretty complicated and involve the mechanism of counter steering, which is used to change the lean angle.
  • #1
Adrian Baker
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The forces acting on a cornering motorcyle are pretty complicated - particularly so the mechanism of counter steering whereby you turn the front wheel the opposite way to the one you wish to travel in (and vice versa when you want it to sit up).

However, when the bike is STABLE in a long sweeping bend with no change in speed or lean angle, what forces are then acting to keep it in its circular path?

The front wheel here has little (no?) effect whatsoever I think, as, if the road drops away, and you have the throttle well open, the bike continues in a curved path, quite happily, with the front wheel off the ground.
 
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  • #2
Well, there is the combined effect of having an angle with the vertical, and the turning of the wheel. When the curve is long, these two factors are so slight that they may be unobservable. When the front wheel is risen there will have to be a slight angle, there's no other way.
 
  • #3
Adrian Baker said:
The forces acting on a cornering motorcyle are pretty complicated - particularly so the mechanism of counter steering whereby you turn the front wheel the opposite way to the one you wish to travel in (and vice versa when you want it to sit up).
Counter-steering is used to change the lean angle. A bit of counter-steering is needed to maintain a lean angle because the self-correction in the geometry (trail). At high speeds, the self-correction is dampened out by gyroscopic forces, requiring counter steering to straighten up. At slower speeds, you can just relax on the handle bars and the bike will straighten up on it's own.

The front wheel here has little (no?) effect whatsoever I think, as, if the road drops away, and you have the throttle well open, the bike continues in a curved path, quite happily, with the front wheel off the ground.
Assuming that you're not a maximum lean where the bike would just slide out, doing wheelies while cornering increases the conrering radius severely. It's possible to turn while doing a wheelie, just like driving an unicycle, but this is a very low g-force turn.

You can visit http://www.uponone.com, which includes a video of a guy doing some cool slow speed wheelies including 360 turns.
 
  • #4
Jeff Reid said:
... A bit of counter-steering is needed to maintain a lean angle because the self-correction in the geometry (trail). At high speeds, the self-correction is dampened out by gyroscopic forces, requiring counter steering to straighten up.

That makes sense, thanks. Much research seems to be on turning into and out of bends, but not on the stability you experience midcorner. It is also hard to judge where and if you are countersteering when in a long sweeping corner. Something opposes your weight pulling the bike down though - particularly so when you think how far sidewards bike racers can lean.

On fast twisty bends, the force you need to apply to the bars on my Ducati to turn in quick is really high, but mid corner it feels like you could take your hands of the bars.
 
  • #5
I just found an excellent website that seems to explain it all. Well worth a look:

http://pdmec4.mecc.unipd.it/~cos/DINAMOTO/indexmoto.html [Broken]

The posters (in Italian and English) are very nice.
 
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  • #6
A bit of counter-steering is needed to maintain a lean angle

Of course, if you hang off to the inside of the bike while turning, it may be enough to overcome the self-correction, and this would affect what steering input would be required to maintain a lean.
 

1. What is the main force that keeps a motorcycle stable while cornering?

The main force that keeps a motorcycle stable while cornering is the centripetal force. This force is directed towards the center of the turn and is provided by the friction between the tires and the road surface.

2. How does the weight distribution of the motorcycle affect its stability while cornering?

The weight distribution of the motorcycle is crucial for maintaining stability while cornering. As the motorcycle leans into a turn, the weight of the rider and the bike shifts to the side of the turn, which helps to maintain balance and traction.

3. How do the front and rear tires work together to keep the motorcycle stable while cornering?

The front and rear tires work together to provide stability while cornering. The front tire is responsible for steering and maintaining the direction of the motorcycle, while the rear tire provides the necessary traction to keep the motorcycle from sliding out of the turn.

4. How does the speed of the motorcycle affect the forces acting on it while cornering?

The speed of the motorcycle plays a significant role in the forces acting on it while cornering. As the speed increases, the centripetal force needed to maintain stability also increases. At higher speeds, the rider must lean further into the turn to counteract the centrifugal force and maintain balance.

5. What are the potential dangers of cornering on a motorcycle and how can they be avoided?

Cornering on a motorcycle can be dangerous if not done correctly. The most common danger is losing traction and sliding out of the turn, which can be caused by factors such as excessive speed, improper weight distribution, or poor road conditions. To avoid these dangers, it is crucial to maintain a safe speed, distribute weight evenly, and be aware of road conditions before entering a turn.

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