Why Do Motorcycles Turn When You Lean? (Explained)

One of the most exciting parts of motorcycle riding is how it leans through the corners.

Rather than turning the handlebars to the left and right the way you would turn a steering wheel, you can turn a motorcycle by leaning your body towards the direction you want to go.

There are more than a few skilled riders capable of leaning into turns at high speeds but have never stopped to ask themselves why motorcycles do turn when they lean.

Here’s the Short Answer to Why Motorcycles Turn When You Lean:

Motorcycles turn when you lean due to the centripetal force of the bike’s lean angle, which is accounted for in its engineering, and the inertia that results as a reaction against the force of the bike’s lean. Countersteering or counter-leaning utilizes that inertia to keep the bike up.

The tire profile is also a significant part of the motorcycle’s lean-angle equation. So, using the proper tires impacts the motorcycle’s handling.

The outer edges of most tires have a smaller diameter than the center, causing the tire to roll along like a cylindrical can that rolls across a flat surface.

When the rider leans the motorcycle over, the tire now functions like a cone-shaped funnel rolling across a flat top at an angle, following a curve instead of rolling in a straight line.

Photo by CanaryRide

Why Do Motorcyclists Lean into a Curve?

When your motorcycle enters a curve, the friction between the road and the tire manifests as a centripetal force -the force of a spinning object. That force jolts the bike’s center of gravity, which can cause it to tilt against the curve.

Leaning into the turn allows the tire to follow its direction instead of tipping against it. 

Countersteering is what we call applying pressure on the handlebars in the opposite direction of the turn, triggering a gyroscopic reaction in the front tire.

To compensate for the counter input, the tire behaves like a cone and follows the road curve instead of rolling straight like a rolling cylinder.

• Powerful natural forces at work keep your motorcycle upright while you’re in motion.
• Therefore, leaning a motorcycle requires working against the generally beneficial forces that keep the bike standing up and riding straight.

So, as the name implies, countersteering is pushing against the direction you want to turn to trigger a reaction in the front tire. 

If you want to turn right, press forward and down on the right side of the handlebar just as you’re moving into the curve. Similarly, you should press forward and down on the left handlebar to initiate a left-leaning turn. 

The force you’re applying on your handlebar is shifting the tire to the side, where its curvature and lean angle can function like a cone instead of a cylinder.

Throwing the tire onto its side lines the tire and, therefore, the whole motorcycle move up with the curvature of the road, triggering the inertia and gyroscopic forces that balance against the gravitational pull of the ground to lock the bike in place until the road straightens out. 

• Leaning your body into the direction of the curve alleviates the pull of the Earth’s gravity on your body, allowing the counter forces to keep the motorcycle upright with less work.
• While body position can help the learning process, countersteering creates the initial force that locks the bike securely into its leaning position.
• Leaning without countersteering can be hazardous, especially when riding fast.

Adding the counterforce to the handlebar force allows riders to turn into curves with much more accuracy and stability.

Countersteering on the same side of the handlebar while pushing against the direction of the curve leans the bike immediately into position. It also stabilizes it during the apex and prepares the rider for a smooth exit acceleration, allowing the motorcycle to stand up on its own as the road straightens out.

Please also check our article about how often you should stop when riding a motorcycle.

How Come Motorcycles Don’t Tip Over When Leaning?

Motorcycles are engineered around their tire physics to provide a specific lean angle the bike can achieve without tipping over. The lean angle is the leaning position where the tire section and centrifugal force are pitted against each other, offsetting the center of gravity, so the motorcycle doesn’t fall.

MotoGP Race bikes, for example, are engineered with lean angles as drastic as 60 degrees thanks to the stiction force of the tire, which is provided by the compound, tread, traction, adhesion quality, radial support, curvature, and shape.

And while the lean angle on an everyday commuter bike is less drastic than a racetrack moto, the physics function is the same – the quality and inflation of a tire are critical to a bike’s ability to lean without falling. 

Finally, the speed at which the rider is cornering, proper countersteering, and the effect the rider’s position has on the overall center of gravity all factor into keeping a motorcycle from tipping while it leans into a corner. 

Or, as the physics experts at WIRED explain:

The net force is still zero in this accelerating reference frame—and now, the net torque is also zero. Let’s look at the torque as calculated about the point where the wheel touches the ground. The frictional force and the normal force (from the ground pushing up) have zero torque since they are both applied at the point that torque is calculated. That leaves just the torque from the fake [or centrifugal] force and the torque from the gravitational force. They are in opposite directions and so they can cancel. In the non-leaning bike, the gravitational force was pushing right through the torque point so that it produced a zero torque and could not cancel the torque from the fake force.

In short, leaning the bike allows there to be a gravitational torque to balance the torque from the fake force. Leaning prevents you from falling over. 

What Happens If You Don’t Lean Right When Turning?

The front wheel can wobble if you fail to slow down and countersteer before turning a motorcycle.

Turning by steering the handlebars instead of leaning causes the bike to fall into the direction of the curve or lock in the upright position, hitting the wall or falling off the road in the apex.

How Are You Supposed to Lean When Riding Into a Turn?

Beginner riders are supposed to lean the motorcycle the way you’re taught in the entry-level motor safety course. Most sources teach a version of this: slow-downshift-look through the turn-counter-steer into the turn-throttle out of the apex to straighten out.

1. As soon as you see a turn or a curve coming up, slow the motorcycle to a manageable speed while matching traffic, downshifting as needed. Make sure you check why motorcycles die when slowing down.
2. Look through the apex of the turn, assessing the direction and angle. Keep your eyes on the height of the turn, and the bike will naturally work its way toward it.
   
   
3. Countersteer your motorcycle by pressing down and forward on the handgrip of the direction in which you need to lean – left to lean left, and right to lean right.
   
   
4. Countersteering while looking at the curve’s apex should naturally shift the center of gravity of your body and the motorcycle into the appropriate lean angle, locking the front wheel into the turn of the road.
   
   
5. As soon as you enter the apex of the turn, twist the throttle as you look into the straightway ahead. The extra juice will pull your bike through the curve, at which point it will naturally stand upright. Follow its lead with your center of gravity to bounce back into the saddle. 
   
   
6. This technique is best mastered through experience, so we suggest learning from a teacher at an entry-level Motorcycle Safety Course.
   
   
7. Once you get comfortable with the method shown in the entry-level safety course, an advanced riding course can teach you the Chin Over Wrist (C.O.W.) technique.

Once you get comfortable turning at slow speeds, you may realize you can take turns faster and sportier as you lean more and more into the curve.

As your speed increases, so does your lean angle and countersteering to avoid falling or exiting the road at the apex of the curve.

You can also check out our article on whether Indian motorcycles are good for beginners.

If you find yourself at the limit of your lean angle and your pipes or luggage is scraping in your curve, it’s time to have a pro teach you the Chin Over Wrist technique in an advanced riding course.

Simply put, the C.O.W. method is leaning your upper body towards the inside of the curve by hovering your chin over your wrist. Some riders go as far as to slide their butt toward the inside of the turn. 

The C.O.W. method moves the center of gravity towards the inside of the curve, so your motorcycle stays in line with the curve with less motorcycle lean angle. Lowering your body weight allows the bike to lift itself while maintaining its curvature.

Final Thoughts

The motorcycle safety course covers proper turning, riding into curves, and technical cornering. These techniques should be practiced and mastered in controlled environments before being attempted on trafficked roads.

Furthermore, turning at high speeds is reserved for advanced riders and are most successfully learned from teachers in advanced riding courses.

Mind you, reading this article is not an adequate substitution for a safety course, which should be completed before attempting to ride a motorcycle through a turn or in any situation.

Sources

How Do Motorcycles Lean So Far Without Tipping Over? | WIRED

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