The rear brake is the most...
The rear brake is the most misused control on a motorcycle, but offers multiple advantages such as increased stability in a panic stop and the ability to adjust your speed through the middle of a corner.
A motorcycle’s rear brake is used differently by nearly every rider. Some riders find it inherently easy to manipulate the pedal, whereas others avoid the control altogether. Neither rider is wrong; there are instances when the rear brake can help and others when it’s deemed unnecessary.
Canyon roads offer a number of rear-brake opportunities, although the varying speeds mean the benefits – and reasons for using the brake – vary drastically. Biggest difference is that you can use the rear brake to adjust your speed through the middle of a corner. If you find yourself carrying too much speed through a sweeping turn, for example, hold the throttle steady and apply a small amount of rear brake to scrub some speed and tighten your line. Applying the front brake and/or chopping the throttle, in contrast, will transfer an adverse amount of weight onto the front tire and test tire traction limits, which could ultimately result in a crash. In all cases, using the rear brake will flatten the bike out and make it steer a small amount slower, but the added stability quickly offsets what’s lost in regards to agility.
The rear brake is used less frequently at the racetrack, although the stability that you garner from tapping the lever is still beneficial in certain conditions. Professional riders use the rear brake to keep the front end down under acceleration. If you’re riding anything smaller than a superbike-spec literbike, then you’ll rarely feel the need to touch the pedal at the exit of a corner, but it’s a skill worth being comfortable with in case you find the front end rising excessively at the exit of any particular corner.
Weight transfer under deceleration will directly affect how often you’ll use the rear brake, and here’s where the racetrack versus street argument gets interesting. The difference is that on the track, aggressive braking transfers an abundance of weight toward the front of the bike. With very little weight left on the rear wheel, the rear brake becomes noticeably less effective.
An aggressive stab at the...
An aggressive stab at the front brake lever transfers an excessive amount of weight onto the front tire, which renders the rear brake useless in certain situations. On the street, a less aggressive pull results in the rear tire being more planted to the tarmac, which offers a greater opportunity to use the rear brake. Increased stability is a primary benefit.
The data in Figure 1 and 2 depicts the difference between weight transfer on the street and track. Figure 1 shows data for an experienced racer at Chuckwalla Valley Raceway, whereas Figure 2 shows data for the same rider on a local canyon road; the black traces depict speed (scale on the left), whereas the red traces depict how much weight is on the rear tire (scale on right, in kilograms). Notice that on the track there are multiple occasions where the rider transfers all of the bike’s weight onto the front tire, leaving none on the rear tire. Even if he did use the rear brake, there’d be no effect in terms of deceleration performance or stability. With the rear wheel in the air or nearly off the ground, the rear brake is rendered useless.
On the street, the rear brake can be used more effectively simply because you’re using less braking force and consequently there is more weight on the rear tire to use for braking traction. Notice in Figure 2, for example, that there is rarely less than 100 kilograms of weight on the back tire, meaning the rear tire is still planted to the tarmac. Using the rear brake in this occasion will therefore have a greater influence on the bike’s handling characteristics.
The rear brake is one of the most misused controls on a motorcycle, which is why it’s important to better understand its benefits in different situations. Accustom yourself to your binder’s performance by using it first in a controlled environment, and then use it accordingly on your next outing. Proper application will undoubtedly make you a safer rider both on the street and at the track.