Tomfoolery – Light Makes Right
When it comes to sportbike performance I’ve always advocated for lighter weight over higher horsepower. A few recent events have augmented exactly why concentrating on weight reduction is time and money better spent than on increasing power production.
Soon we’ll be posting Sean Alexander’s exclusive first street test of Kawasaki’s H2. We dyno’d Team Green’s supercharged halo bike to the tune of 193.7 hp at 12,000 rpm and 92.2 lb-ft of torque. Impressive figures, to say the least. Less impressive is the H2’s wet weight of 525 pounds, giving the H2 a ratio of 2.7 pounds per horsepower.
Comparably, BMW’s S1000RR, the horsepower winner of our forthcoming superbike shootout extravaganza, spun the drum to an equally impressive 182.9 at 13,100 rpm and 79.9 lb-ft at 9600 rpm, giving it a ratio of 2.5 pounds per horsepower. Not a huge disparity in straight line performance between the two but a significant detriment to the H2’s braking and cornering prowess.
I understand the H2’s not a race bike. Kawasaki has the ZX-10R for that. Having accompanied Alexander during the street test of the H2 I can attest to it being a wonderfully balanced street motorcycle with a superbly stable chassis and braking power to match the bike’s insanely fast propulsion. But here’s where things get interesting.
Weighing 170ish, I have, give or take, a 70-pound weight advantage to Sean’s 240ish. Our first top-gear roll-on test with me aboard the BMW and him aboard the H2 was a clear win for the BMW. A second attempt cemented the BMW’s dominance, or so we thought. Swapping bikes – adding his 70 pounds to the BMW and lightening the H2’s load by 70 pounds with my body weight – gave the top-gear roll-on win to the H2.
Another, more extreme example of weight vs horsepower is when EiC, Kevin Duke aboard the Honda CBR1000RR SP (150.4 hp at 10,500 rpm and 76.4 lb.-ft at 10,100) was pulling away from Alexander on the BMW S1K down Laguna Seca’s front straight during our superbike test. Duke enjoys a 95-pound weight advantage over Alexander but the Honda suffers a 32.5 horsepower deficit to the BMW.
I know, I get that I’m talking about rider weights, but if you apply what’s so apparent in these examples to reducing the weight of a motorcycle you get my point. By lessening a bike’s weight not only do you achieve better acceleration, but also reap the benefits of a motorcycle that stops and turns better than its heavier, bigger horsepower counterparts.
It seems as though liter-class sportbikes have been stuck in the mid-400 pound weight category for quite some time and I’m unsure the reasons why. Yamaha’s new R1 with an aluminum fuel tank, and magnesium wheels and subframe tipped the scales at 438 pounds wet – a 16-pound reduction from the 454-pound claimed wet weight of the 2014 model. The original 1998 R1 weighed approximately 448 pounds full of fluids. Using it, that’s an average annual weight reduction of about a half-pound per year over 17 years. At least Ducati’s monocoque frame design of the Panigale gets its wet weight down to 427 pounds.
As much as I like the H2 and all its supercharged badassery, what would really make my hair stand on end would be the introduction of a new superbike producing a mere 150 horsepower but weighing 395 pounds dripping wet for a more affordable price than Honda’s RC213V-S. That’s a perfectly acceptable power to weight ratio of 2.6 pounds per hp, square in the middle of the BMW and H2. At the current average rate of reducing weight by a half-pound per year it’ll take about nine years to get there. I’d like the OEMs to speed up the process because any advantage gained at their current rate of weight reduction will be negated by my accelerating rate of middle-age weight gain.