Will changing my rear tyre affect dyno results?

Published: 22 June 2011

Q. My bike used a 190/55 x 17 rear tyre as original equipment, but now it’s on a 190/50. Will there be a difference in rear wheel torque as a dyno measures it on the rear wheel? Motorcycle tyres for sale
Conrad Taute, email
 
A.
Inertia dynos are the most common and the short answer is no. In simple terms inertia dynos calculate power by measuring the acceleration of a heavy steel drum of a known mass.

If you were to change tyre diameters during a dyno session the run start and end drumspeed would certainly change, along with the run time.

However, the important part is the rate of acceleration, and that would not change, hence thedyno would read the same horsepower. The same thing applies if you change gear during a dyno session.

However, tyre compound can affect dyno readings, on high horsepower bikes (190hp+) Dynojet regularly see up to 8hp difference between different compounds. If you are running the same bike regularly on a dyno always use the same tyre to ensure consistency.

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