# Bicycle & Motorcycle Turning Dynamics: Leaning to Balance Forces

• sganesh88
In summary, the wikipedia article explains that in order for a bike to turn, it must lean to balance the forces acting upon it. This includes gravitational, inertial, frictional, and ground support forces. The leaning is necessary for the rider to stay on the bike and to initiate the turn. Turning the handlebars alone is not enough to initiate a turn, as the bike will lean in the opposite direction. The goal is to not fall over, so a coordinated turn is needed and countersteering, either through steering or body leaning, is necessary to initiate the roll and achieve a proper lean. However, body leaning only works within a certain speed range. In summary, the article explains the mechanics of turning a bike and how it is necessary
sganesh88
The wikipedia article on "Bicycle and motorcycle dynamics" in the "Turning" section
http://en.wikipedia.org/wiki/Bicycle_and_motorcycle_dynamics#Turning
states
In order to turn, that is, change their direction of forward travel, bikes must lean to balance the relevant forces: gravitational, inertial, frictional, and ground support.

Is this right? I think leaning is done for the rider staying on the bike. (balancing the moment of the friction and the moment of the normal force about the C.G) and not for initiating the turn. comments?

So, how are you suggesting that turns are made? Do you think by turning the handlebars? Go try it - try to turn the bars right, and you will lean over to the left and turn left (as long as you are moving with some speed). If you don't believe this please go try it before replying.

So, how are you suggesting that turns are made?
So there is no need of friction? Just a torque contributed by the normal force is enough? Those silly guys are unnecessarily providing handle bars then. God forgive them!

A bike turns (the center of mass accelerates "inwards"), when ever the tires apply an outwards force to the pavement, which coexists with an equal and opposite inwards force onto the tires. The force produces an inwards acceleration and rolling torque on a bicycle. If the bicycle isn't leaned sufficiently for gravity related torques to counter the steering related torques, the bicycle will roll outwards. Note that the rate of inwards acceleration is equal to the inwards force from the pavement divided by the mass of the bicycle, regardless of any roll reaction.

Normally the goal is to not fall over, so a somewhat "coordinated" turn is needed, and countersteering, either directly through steering inputs, or body leaning, which results in a brief outwards steering of the front tire is needed in order to initiate the roll to achieve a proper lean. Note that body leaning only works within a speed range.

gmax137 said:
Turn the bars right, and you will lean over to the left and turn left.
Not quite. Turn the bars right, and the bicycle will turn right while rolling left, ending up on it's left side, but having turned right in the process. The side force determines the rate of inwards acceleration, independent of any roll reaction of the bicycle, the caveat here is to note that for a given steering input, the side force will be less if the bicycle experiences outwards roll axis acceleration than if the turn is properly coordinated (or inwards roll axis acceleration).

Then again, it's difficult to turn a bicycle that is sliding on its side after falling over.

Last edited:

## 1. How does leaning affect the balance of a bicycle or motorcycle while turning?

Leaning is a crucial component of balancing forces while turning on a bicycle or motorcycle. When the rider leans into a turn, the center of gravity shifts towards the inside of the turn, creating a counteracting force that balances the centrifugal force pulling the bike outward. This allows for a smooth and stable turn.

## 2. What is the role of centrifugal force in bicycle and motorcycle turning dynamics?

Centrifugal force is the force that pulls an object outward when it is moving in a curved path. In the case of a bicycle or motorcycle turning, centrifugal force is what causes the bike to want to continue moving in a straight line, rather than following the curve of the turn. Leaning into the turn helps to balance this force and keep the bike on track.

## 3. How does the speed and radius of a turn affect the balance of forces while riding a bicycle or motorcycle?

As the speed of a turn increases, so does the centrifugal force pulling the bike outward. This means that the rider must lean more to balance this force and keep the bike stable. Similarly, a tighter turn radius also requires more leaning to balance the forces. It is important for riders to be aware of these factors and adjust their lean accordingly to maintain control.

## 4. Are there any other factors besides leaning that can affect the balance of forces while turning on a bicycle or motorcycle?

Yes, there are other factors that can affect the balance of forces while turning. The weight distribution of the rider and the bike, as well as the condition of the tires and road surface, can all play a role in the bike's stability. Additionally, the rider's steering and braking techniques can also impact the balance of forces while turning.

## 5. How can understanding bicycle and motorcycle turning dynamics improve riding skills?

An understanding of turning dynamics can greatly improve riding skills by helping riders to anticipate and properly respond to the forces at play while turning. By knowing how and when to lean, adjust speed, and use steering and braking techniques, riders can navigate turns more smoothly and safely. This knowledge can also help riders to better control their bikes in unexpected situations, such as sudden obstacles or changes in road conditions.

Replies
34
Views
1K
Replies
3
Views
2K
Replies
10
Views
1K
Replies
86
Views
13K
Replies
16
Views
2K
Replies
14
Views
2K
Replies
4
Views
4K
Replies
2
Views
2K
Replies
11
Views
8K
Replies
46
Views
7K