Zero-To-60 MPH Measured On A Dyno?!

Four good reasons why the number is nonsense.

Zero SR/F
Time to speed can only be measured by actually taking time to speed—in the real world. We analyze how an erroneous “0-60-mph” time for the Zero SR/F measured on a dyno is not accurate data.Monti Smith

In a story entitled “2020 Zero SR/F Electric Motorcycle First Ride” published on our website, we erroneously stated that this machine achieved a 0-60-mph time of 1.57 seconds, without clarifying that the figure was obtained with the bike stationary on a dyno. Which is, of course, not actually a measurement of “0-60 mph.” As a result, the time is roughly a second faster than some of the quickest motorcycles ever tested by this magazine.

Fortunately, we had since performed a full test of the Zero SR/F including CW’s normal dragstrip testing, where its time was 3.7 seconds in the hands of Road Test Editor Michael Gilbert. This is a real 0-60-mph time because it was achieved on actual pavement by a human rider on an accelerating motorcycle. Publishing that dyno 0-60-mph run was an error; we should have edited the number out or provided some context and explanation. If, for example, we had shown the dyno 0-60-mph times recorded in different power modes, it could help us understand the relative performance delivered in each mode. We apologize for the error.

Publishing “data” like this is also a particularly good way to get your Technical Editor riled up. Kevin Cameron weighs in:

Let us count the ways in which this case differs from reality.

1. On a dyno, the bike is strapped down so it cannot wheelie. Normally, the maximum acceleration of any powerful bike is limited by front-wheel lift. That’s why dragbikes are very low, have very long wheelbases, and have wheelie bars. Otherwise, they would flip over backward.

2. The strapping down greatly increases tire traction, just as a Formula 1 car’s estimated 4,000 pounds of high-speed downforce greatly increases its tire grip, enabling it to corner, brake, and accelerate far harder than non-downforce vehicles. The grip of motorcycles—electric or combustion-powered—depends upon gravity alone.

3. What is being accelerated on a roller-driven acceleration dyno is not a bike and rider but a heavy roller whose rotational inertia has been arbitrarily chosen to represent some kind of “average motorcycle.” We don’t know whether the roller has more or less inertia than a given actual motorcycle plus an average rider; this fact does not affect the horsepower accuracy of such dynos.

4. Although aero drag at 60 mph is not large, on a roller dyno there is zero aero drag at every speed.

Dyno test zero sr/f
The Cycle World Dynojet dynamometer is a rear-wheel inertia dyno great for measuring the relative power output of testbikes, but should not be cited for measuring “acceleration testing.”Cycle World

Unfortunately, this false 0-60-mph time was quoted in a story by the Los Angeles Times as if it were the result of CW’s normal dragstrip testing. We notified the Times about the error and have provided it with the actual test numbers from our normal careful motorcycle performance testing.