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[tonylai]

I've built a electric motorcycle with two hub motors (no gear ratio) which are directly drive by two independent but same controllers and same throttle.
If throttle is turned, two wheels will be drive at the same time with same throttle signal but a little different speed due to the difference of the radius.
The front RPM and rear RPM are approximate but I don't know how to calculate the vehicle's speed by these two RPM since they are both driving.

Assume the front RPM is 246, radius is 0.24 meter, which the wheel's speed is equals to 22.25km/hr.
The rear RPM is 250, radius is 0.25 meter, which the wheel's speed is equals to 23.56km/hr.
Can the velocity of the electric motorcycle be 22.905km/hr?
If not, how can it be calculated?

Thanks for your reply!

[Fred]

If those measurements are correct then the back wheel may indeed be moving at a faster linear velocity. It might be losing grip and your traction control (if you had it) would need to kick in and reduce power to the rear wheel. The other option could be that the front wheel is in the air. 

[TheRan]

Are those results with the wheels off the ground? As Fred said, if they're on the ground the calculated speed should be the same unless one of the wheels is losing traction. You don't really need to monitor the speed of both wheels anyway unless you're doing traction control, just pick one and use that for the speedometer like every other motorcycle does.

[tonylai]

If those measurements are correct then the back wheel may indeed be moving at a faster linear velocity. It might be losing grip and your traction control (if you had it) would need to kick in and reduce power to the rear wheel. The other option could be that the front wheel is in the air. 

Are those results with the wheels off the ground? As Fred said, if they're on the ground the calculated speed should be the same unless one of the wheels is losing traction. You don't really need to monitor the speed of both wheels anyway unless you're doing traction control, just pick one and use that for the speedometer like every other motorcycle does.

The electric motorcycle is indeed off the ground, but I've tried the road test, and the velocity is so fast that I can only turn the throttle for like 2 sec and the highest speed of both hub motor (if my A/D calculate is right) is about 335 RPM (22 km/hr).
So I can say that my motorcycle's velocity is 22km/hr?