5.2 Braking and Emergency Swerving

Braking and Emergency Swerving

Operating a motorcycle requires a high level of braking proficiency. Because motorcycles have separate controls for the front and rear brakes, stopping safely and quickly is a multi-step physical skill. Under normal conditions, braking is a routine task; however, in emergency situations, the rider's ability to maximize stopping power without locking the wheels is the difference between a safe stop and a severe crash.

Brake Force Distribution: The 70/30 Rule

A motorcycle's braking capability is heavily biased toward the front wheel. Under normal stopping conditions, the front brake provides approximately 70% of the vehicle's total stopping power, while the rear brake provides approximately 30%.

This distribution is a result of dynamic weight transfer:

• As brakes are applied, the motorcycle's momentum shifts weight forward onto the front wheel.
• This weight transfer compresses the front suspension, pushing the front tire into the pavement and increasing its contact patch and traction.
• Conversely, the weight shifts off the rear tire, reducing its contact patch and making it much more susceptible to locking up and sliding.
• In emergency braking scenarios where deceleration is extreme, the front wheel's contribution can rise to 90% or even 100% of the total stopping force as the rear wheel lightens completely.

Riders must always use both brakes simultaneously for every stop. Relying solely on the rear brake increases stopping distances by up to three times, while relying solely on the front brake fails to utilize the rear tire's traction and can upset the chassis if not applied smoothly.

Correct Braking Technique

To achieve maximum stopping efficiency (threshold braking), a rider must follow a precise sequence:

1. Squeeze the front brake lever smoothly and progressively: Do not grab or snap the lever. Grabbing the lever applies maximum braking force before weight has transferred to the front wheel, causing the front tire to skid immediately. By squeezing progressively, you allow the front suspension to compress and load the tire, maximizing grip.
2. Apply progressive pressure to the rear brake pedal: Press down on the pedal smoothly. As the stop progresses and weight transfers forward, you must lighten pressure on the rear pedal to prevent the rear wheel from locking up.
3. Pull in the clutch: Just before coming to a complete stop, pull the clutch lever in to prevent the engine from stalling. Downshift to first gear so you are ready to accelerate immediately if traffic conditions require it.

Handling Wheel Lockups

• Front-Wheel Skid: If the front wheel locks up, you must release the front brake lever immediately and then reapply it smoothly. A locked front wheel loses all steering control and will cause a crash within a fraction of a second if not released.
• Rear-Wheel Skid: In Alberta, if the rear wheel locks up on a dry surface in a straight line, the general advice is to keep the rear wheel locked until you come to a complete stop, keeping the motorcycle aligned in a straight line. Releasing a locked rear wheel when it is out of alignment with the front wheel can cause the motorcycle to suddenly regain traction violently, throwing the rider off in a high-side crash.

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Braking in a Curve vs. Straight Line

Tires have a limited amount of traction, which must be shared between cornering forces (leaning) and braking/acceleration forces. This is known as the traction circle concept.

• In a straight line, 100% of tire traction is available for braking.
• In a curve, a large portion of traction is consumed by keeping the motorcycle turning. If you apply hard braking while leaned over, you exceed the traction limit, causing a slide.

If you must stop quickly in a curve, the safest method is to straighten the motorcycle first, then apply maximum straight-line braking. If you cannot straighten the motorcycle due to lane boundaries or obstacles, you must apply both brakes with extreme smoothness and much less pressure, gradually increasing braking force as the motorcycle is stood upright.

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Emergency Swerving

When there is insufficient distance to stop before hitting an obstacle, a swerve is required. A swerve is a rapid path correction consisting of two quick countersteers: push left to steer around the hazard, then push right to recover your lane position.

Critical Rules for Swerving

• Never brake while swerving: This is the most critical rule. You can brake before the swerve or after the swerve, but you must completely release the brakes while executing the swerve. Applying brakes while performing a maximum-effort lean will exceed the tire's traction limit, causing an immediate crash.
• Keep knees tight: Keep your knees firmly pressed against the fuel tank to stabilize your body on the motorcycle.
• Look at the escape path: Look at the space around the obstacle, not at the obstacle itself.