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Best roller diameter for motorbike dyno?

Practical Standalone Tuning

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Hi guys! I want to build motorbike dyno and now I am thinking of roller diameter for inertia dyno. Try to choose between 325 and 350 mm (both about 450 mm lenght). Will be used for modern bikes so, it have to be ok for 200 +- hp. Any ideas?

I would expect a larger diameter to be better for traction. Size may depend on what machining process can be used provide a grooves / grid for traction. Have you calculated the desired inertia mass for these two sizes?

Yes, dynojet 250i motorcycle dyno has 450 mm diameter roller and about 14 kg/m^2 inertia. 350 mm roller which is the most popular in our country has only about 6 kg/m^2 of inertia. Huge difference. Don't know why is that...