WHAT DOES A DYNO DO?
Dynos, or dynamometers, are fairly simply pieces of equipment – the clever part is interpreting the data they generate. While you do get engine dynos that measure the power of a static motor, most of us will only ever encounter a rolling-road dyno, which is used to test the power of a complete motorcycle. A dyno consists of a static platform, which is used to support the motorcycle and stop it breaking free, and a large drum under the rear wheel. This drum weighs in the region of 200kg and is very accurately machined to ensure it is perfectly balanced, as any imbalance would cause data errors. The surface of the drum is knurled so that the bike’s tyre can grip, not slip. Generally a dyno will measure what is known as tractive force, which is the force the bike’s tyre uses to turn the drum. As the inertia of the dyno’s drum and also the resistance of the bearings are known parameters, the computer can calculate how much force the bike is exerting during an acceleration run, thus enabling this force to be expressed as horsepower and torque, which are then plotted against the bike’s revs. These charts can have various correction factors applied them to standardise the results, taking into account variations in temperature, air pressure and humidity.