In order to fully test the braking systems on each bike, we used our Racepak G2X data acquisition system to record a series of stops with Kento at the controls, and looked at stopping distances as well as braking deceleration (in G) for each stop. In addition to pointing out performance differences between the three bikes, it’s also worthwhile pointing out some details about braking in general that is shown in the data.
Note that the stopping data is shown here relative to distance, and the speed traces drop sharply as speed approaches zero. Here you can see an important aspect: Even at maximum braking, it takes exponentially more distance to slow from a higher speed than a lower speed. This is why it is critical in any sudden stop to get to maximum braking as quickly as possible. Note also that it takes a certain amount of time (and distance) to get to maximum deceleration, as shown in the braking G plots. This is a function partly of the rider’s ability to get to maximum braking, but also how quickly weight is transferred to the front wheel without it going into a skid. ABS can help somewhat in this aspect, but the rider’s skill also plays a big part. Again, this shows how important it is to master all aspects of braking, both for quick lap times on the track and safety on the street.
Because of the friction relationship between a tire and the road surface, the maximum deceleration typically generated on clean, dry pavement is approximately 1 G. Another limiting factor, however, is the motorcycle’s rear wheel lifting off the ground. Due to the relationship between a typical sportbike’s wheelbase and the position of its center of gravity, this also occurs at about 1 G of deceleration. By fitting each bike with identical tires (see sidebar) we eliminated one variable in the equation, but each bike’s weight distribution does affect its braking performance. In addition, the rider can improve that weight distribution by sitting further rearward on the seat and not raising his torso excessively.
For each bike, we had Kent perform three sets of three stops: one stop with the rear brake only, one with the front brake only and one with both; that sequence was repeated three times. The best stops using rear-only, front-only and both brakes are shown here displayed as speed over distance and braking force over distance. Because it’s practically impossible to begin each test from an identical speed, we lined all the data up at 60 mph and calculated stopping distance from that point, as is typical in the industry. Note that the deceleration diagrams (Braking G) begin ramping up at different points, not because of any performance discrepancy, but because the starting speed of each test is slightly different.
To account for the BMW’s changing ABS in the different riding modes, we ran the test in both Sport and Slick modes. Sport mode offers ABS on both wheels and limits the rear wheel from coming off the ground, while Slick mode deactivates the rear-wheel lift feature as well as deactivates ABS on the rear wheel when the rear brake pedal is used.
Rear Brake Only
The Honda has a huge advantage in rear-brake-only stopping thanks to its Combined ABS activating the front brake, with a stopping distance more than 50 feet shorter than the Kawasaki, which has the next shortest distance. The BMW took more distance than those two bikes, with a significant difference between Sport and Slick modes; Kent reported the rear brake definitely skidding in Slick mode, hurting the stopping distance. Kent also pointed out that the Kawasaki’s rear brake is quite high-effort, but still capable of activating the ABS. In the braking G chart, note that (obviously) the Honda has the highest deceleration (close to .6 G), but also that there is a definite point (at about the 25-foot mark) where the front brake kicks in and adds that extra deceleration. The Kawasaki shows an almost constant value over the course of the stop, approximately .45 G while the BMW tapers off in the middle of the stop in both modes.
Front Brake Only
While the 60-0 mph stopping distances using front brakes only are almost identical for all three bikes (and the BMW in both modes), there are some significant differences in performance seen on the braking G chart. The Kawasaki has a slight advantage in stopping distance, and the braking G shows the ZX-10R ramping up to its maximum deceleration of .95 G quicker and smoother than the other bikes, holding that steady over the course of the stop and tapering off slightly as the bike comes to a stop. By reaching maximum G earlier, when the bike is going faster, the Kawasaki posts a shorter stopping difference; this performance edge would be magnified in stops from a faster speed.
The BMW, in both modes, takes slightly further to get to maximum braking G but also holds a consistent value over the course of the stop. The Honda takes the furthest distance to ramp up to serious braking G. Again, however, there is a noticeable step where the system activates the rear brake and adds to the stopping power, with braking G rising from an early plateau of approximately .8 G to .94 G, almost matching the Kawasaki later in the stop.