Braking Styles On Motorcycles - Code Break

Braking, it turns out, does much more than just slow you down. Fork flex, geometry changes, tire deformation and a host of other forces come into play, drastically affecting the way the motorcycle negotiates a corner. The forward pitch of the bike under braking can steepen the fork angle by as much as 4 degrees on a Ducati 1098, for example. This reduces trail by roughly an inch on the same hypothetical 1098, and effectively shortens the wheelbase as well. Front-wheel load can double under heavy braking. Tire height shrinks under load, further decreasing trail by a slight amount. At the same time, however, the contact patch both broadens and lengthens rearward, which can restore trail by as much as 1 inch. Trail is now close to where it started, unless the tire locks up-at which point you'd have very little stability, owing to an instant reduction of trail. Braking doesn't sound so simple anymore, does it?

Even the best forks flex under braking. This flex creates "stiction," a term that describes a fork's action becoming sticky from internal friction. That, in combination with heavy spring compression, reduces tire compliance with the road. Finally, frame flex can introduce a negative loading-and-unloading influence as well.

There are two primary methods of braking for a corner: straight-up braking, where you complete braking before turn-in, and trail braking, where you stay on the brakes after turning and feather off brake pressure as you near the apex. When trailing the brakes into a corner, still more forces come into play. Additional drag is created on the inside edge of the now-larger contact patch. That drag twists the fork inward, which tends to counter-steer the bike back up out of its lean.

On a well-designed bike with proper geometry, the fork rotates side-to-side to maintain tracking and stability. Under the above conditions, it is heavily restrained. This promotes an increase in bar-twitch. The tire, stretched in at least three directions, puts enormous and conflicting stresses (and releases) into it the fork motion too. All of these factors can contribute to a heavy, sluggish feel at the bars.

Under all cornering situations, the tires are slipping. In fact, depending on speed and corner radius, the wheels rotate as much as 10 or 20 percent slower than the vehicle's velocity, scrubbing off both speed and rubber from the tires. This often-forgotten fact is called "slip angle," and adds to the tendency to lose traction from the front tire under extreme trail-braking situations.

On the positive side, the steeper fork attitude and shorter wheelbase allow the bike to carve a sharper turn given the same amount of lean angle. Adding to this positive effect is an ever-tightening cornering radius that results from the decreased speed. And don't forget the rear tire-unloaded under heavy braking, it takes less effort to turn. Engine rpm and wheel speed decrease at the same time, reducing gyroscopic effect from the rotating masses of both.

What this all means is that somewhere between initial turn-in and final release, the bike is able to achieve its tightest turning arc. This can provide a highly skilled rider with subtle control of both his cornering line and corner speed.

Straight-up braking inspires less physical drama, but still demands intense attention from the rider. In some cases, completing the braking act before you turn is more difficult than trail braking to the apex. In this case, the bike's turning arc must be established before the turn is initiated. The ability to predict line, apex and exit is vital. This requires, among other things, superlative visual skills. In addition, quick and accurate steering is a must. The rider must have enormous confidence in front and rear tire grip before flicking the bike into the turn. Coordinating brake release and turn-in steering actions must be spot-on, or the suspension will rebound as the bike is entering the turn. This all requires deft coordination and impeccable timing.

The reward for such precision is a chance for the rider to get on the gas much earlier, letting the suspension settle into its most compliant range of operation. Additionally, he can better maintain and adjust corner speed, release bar pressure earlier and, with both tires sharing the cornering load, reduce unnecessary lean angle. All of these factors will increase both speed as well as traction and suspension feedback.

The essential difference between trail braking and straight-up braking is which control-the throttle or the brake-is used to adjust the rider's line. Trailing brakes requires excellent front-end feel and is often cited as an advanced technique. Rightfully so-most MotoGP crashes occur under deep trail-braking circumstances. Even so, when you consider the judgment and coordination demanded to skillfully execute quick and accurate straight-up braking entries, I'm not convinced trail braking is the more advanced technique. It may be the other way around.

Brake as hard as you dare straight up and down, but reduce pressure on the lever as you bend it in or you'll bin it! MotoGP racer Alex de Angelis demonstrates.