BRAKING:
WEIGHT TRANSFER AND MAXIMUM PERFORMANCE

Every man takes the limits of his own field of vision as the limits of the world.
—Arthur Schopenhauer

Virtually all crashes are preceded by the rider using his brakes to reduce his speed or to attempt to stop. He must do this before, during or after his (failed) attempts to countersteer, lean and turn. Unlike an automobile, motorcycles have separate controls for the front and rear brakes, further complicating the decision-making process. Riders with off-road experience can be confused by the grip available on smooth, comparatively level asphalt. Learning how to slow down in the shortest possible distance will give a rider maximum protection from injury—and possible DWI arrest.

According to the Hurt Report, incompetent braking is a contributing factor in almost all motorcycle crashes. Like its explanations of countersteering, the government's attempts at teaching braking control appear to be under the influence of amateurs. Beware outdated advice from unaccountable bureaucrats.

The spinning rear wheel is critically important due to it providing the majority of gyroscopic stability, preventing the moving machine from falling over. Locking the rear brake can destroy this stability, therefore the stronger front brake should be used exclusively for 99% of straightline braking situations on asphalt. Most of the bike's weight is pitched forward onto the front tire under braking, practically ramming the rubber into the road which can protect it from lockup. This increasing the probability of rear wheel lockup, especially if it hits a bump.

(illustration 50/50 = 300/300, 90/10 dry = 540/60) "cruising weight distribution" + "hard braking on dry pavement"

Wet weather riding is a rare exception to rear brake useage, since there is 2/3rds less weight transfer due to 2/3rds less decelleration on the wet asphalt. This means there is 2/3rds more weight pressing down on the rear wheel to keep it from locking. (Unlike cornering under acceleration, the larger rear tire does not give greater wet-weather traction while braking, since it has a larger contact patch than the smaller font tire. This means the rear tire contact patch has less weight per square inch, and thus has even less weight available to "squeegee" water out from under the tire.)

(illustration 70/30 wet = 420/180)

According to "The Photographic Analysis of Motorcycle Operator Control Responses," even experienced riders do not realize these facts, and their test riders had exactly the same stopping distances on a wet road as on a dry road, due to underuse of the front brake and overuse of the rear brake on dry pavement. These riders actually had 25% shorter stopping distances with the rear brake locked (which reduces stopping grip) than when using the rear brake "normally," since they could then focus exclusively on the front brake (using more front brake). Had they used the front brake only, dry pavement stopping distances would have been even shorter.

In fact, locking of the front brake in a straight line could only occur at 5 to 10 miles per hour (resulting in a relatively safe "low-side" crash), since there was too much grip at higher speeds due to weight transfer. Front brakes generally are not strong enough to lock due to weight transfer, effectively giving a rider the benefit of "passive ABS." Locking the front brake is often due to a rider's mistake of not using the same amount of braking from start to finish—using less at higher speeds while increasing the braking force as the bike slows down. Applying the front brake smoothly instead of suddenly will prevent the suspension from bottoming out—hitting a bump at that point could bounce the front tire off the road and result in a locked wheel and skid. Turning into a corner with too much front brake can lead to a skid and possible low-side crash—it is best to let off the brake and trust countersteering to do its job.

(stoppie photo) "The rear brake is not required for maximum braking performance."

This report also found that overuse of the rear brake during an emergency swerve maneuver (double countersteer) frequently resulted in a skid. This often resulted in either "laying it down," or if the rider released the brake while sideways, the bike whipped back into "highside" crash. (It is best to not brake hard while countersteering hard. Do the braking before or after countersteering when possible, or be gentler on both and only use the front brake.) This report was conducted over 20 years ago, when some motorcycles had relatively weak brakes (at least one of the test bikes did not have a front disc brake), and it is the source of the government's current bad advice to use the rear brake. Back then, many fearful novices still believed the rear brake should do most (or all) of the braking, so any use of the front brake was an improvement. (However, I did witness a rider in 1998 use only his rear brake to slow down for a traffic jam on a busy Interstate highway.) It is now time to take rider skill to the next level. Using engine compression for rear-wheel braking can have similar repercussions. Note that racers make use of the rear brake to slide the rear tire out from under them while entering a turn ("backing it in"), which is probably not a useful habit for the street.

Emergency braking while in the middle of a corner is another exception—dividing the braking action between two wheels reduces the likelyhood that the front tire will exceed its friction circle limits (described in the chapter on automobiles), resulting in the front tire sliding (not the end of the world—just let up on the brakes a little—but definitely heart-stopping). However, when braking while cornering, inertia and centrifugal force will lift the bike into a vertical position—not a good idea while trying to lean. Riders can get away with cheating during non-emergency cornering (although they may be reinforcing bad habits). Emergency braking in a corner is best performed by straightening the handlebars and allowing the bike to go straight, then let off the brakes and countersteer again (assuming there is room to do so. Otherwise, you had better have worn your leathers).

Locking the front brake is not nearly as likely as locking the rear brake, since most—if not all—of the weight is shifted onto the front tire due to decelleration forces. It is very difficult to lock the front brake in a straight line on dry asphalt. ("Stoppies" are the opposite of "wheelies"—front tire on the ground and the rear tire vertically in the air—and are possible on modern sportbikes by rapid braking. Fortunately, they cannot happen by accident on a street bike, since they require skillfully bouncing the rear suspension spring(s) to launch the back of the bike upward.) Paradoxically, it is best to never use the rear brake except in the rain (three times more weight on the rear wheel), since many crashes occur from its overuse. (Autoracing drivers adjust their brake bias to the rear for wet races). Knowledge of these technicalities and techniques can certainly place a rider in greater control of his vehicle and vastly improve his "chances" of avoiding danger on the road.

Braking performance is also affected by whether the road is uphill or downhill. Going up a steep hill can reduce stopping distance by 25%. Going down a steep hill can increase stopping distance 25%. It is also important for a rider to keep his arms relaxed while braking. This significantly improves braking performance, allowing shorter braking distances with less chance of locking the rear wheel or losing control. Stiff arms transfer the rider's body weight onto the front wheel, while relaxed arms keep his weight over the seat. This gives the front suspension more travel to absorb bumps, and gives more weight to the rear wheel for cornering grip (or braking, if a rider wanted to use the rear brake).

(illustration 99/1 = 594/6) "braking with stiff arms can reduce braking performance"

None of these motorcycle skills are taught by this state's government when it tests drivers' license applicants. In the case of emergency braking, once again the government gives defective advice: "To stop quickly, apply both brakes. Don't be shy about using the front brake. . . . At the same time press down on the rear brake. If you accidentally lock the rear brake, keep it locked. . . . . . . [E]ven with a locked rear wheel, you can still control the cycle on a straightaway as long as your motorcycle is upright and going in a straight line." [Emphasis in original.] Of course, it is impossible to keep a heavy street bike upright without the gyroscopic effect of the rotating rear wheel, which is why the government inserted a disclaimer in their advice in case it doesn't work. (Rather than disclaimers, shouldn't the government teach something that actually works?). A government chart alleges maximum braking is achieved using both brakes, when the reality is that when the front brake is at maximum stopping power, there is little or no weight on the rear wheel making the rear brake useless and dangerous. Maximum stopping can only be achieved by using the front brake alone.

An exception would be an old type of machine with an underpowered front brake. Twenty-five years ago, brakes were weaker than they are today, yet the government information has not been updated. Assuming a rider owns a modern machine, why risk using the rear brake? It's just one more thing to worry about in an emergency.

Smooth downshifts while braking can be achieved by using only the first two (stronger) fingers on the brake lever, allowing the rider to blip the throttle between shifts. Practice until the front end does not rise between shifts. Relying upon engine compression to do the braking, especially when entering curves, is a bad habit that can cause the rear tire to slide suddenly as lean angle increases. Although this "technique" can be temporarily useful for learning how to lean without being distracted by rapid braking, it has the same effect as using only the rear brake—not a good habit while turning. "Cupping" of the rear tire is an indication a rider needs practice on braking and turning correctly. Holding in the clutch lever while braking, releasing it only when ready to accellerate, can eliminate this risk. Racers use this technique on both cars and 'bikes, although a street rider must hold the clutch lever for longer periods of time due to the slower speeds involved.

(illustration cupped rear tire—rough/rear, smooth front) "Cupping reveals poor braking skills"

When using the brakes to reduce speed prior to and during the beginning of the turn, practice a smooth transition into the turn without letting the front suspension bounce back up when finished braking. This requires reducing the braking force at the same time lean angle is increasing. Countersteer to reach a rapid lean angle, then let steering trail take over (arms must be relaxed). Let the centrifugal force compress the suspension an equal amount. This allows maximum braking and maximum cornering grip (and maximum ground clearance). Continue to accellerate slightly throughout the turn, to allow the rear tire to provide its share of the cornering grip. As the turn ends, countersteer again to bring the bike vertical, increasing the accelleration as lean angle decreases. Accellerate harder once the turn is over, and look forward to the next curve of the road. When a rider practices these skills everytime he rides, he will eventually reprogram his brain so that they become effortless. (Riding in the rain still requires straight-line-only braking.) Cornering (correctly) is what riding a motorcycle is all about.

Return to Home Page

Chapter 1. Let's Look at Some Data

Chapter 2. Risk Management

Chapter 3. Two Wheeled Physics

Chapter 4. Countersteering: Cornering Techniques

Chapter 5. Gravity Is a Good Thing

Chapter 6. Gyroscopic Precession: Nature's Power Steering

Chapter 7. Braking: Weight Transfer and Maximum Performance

Chapter 8. Controlling Slides and Tank Slappers: Mind Over Matter

Chapter 9. Group Riding

Chapter 10. Riding Etiquette

Chapter 11. MSF Courses- Editorial