Maths Help Please

[TBirdUK]

My brain is a bit slow today and needs some help.

I have a 10 inch diameter wheel which can give a speed of 4 mph at max revs - what would be the equation and result if I changed the diameter to 16 inches?

Thanks

 

[TBirdUK]

Cheers all, much appreciated - its for swapping out the 10 inch wheels of a mobility scooter for 16 inch ones when I take the drive and put it in my boys jeep - torque wont be an issue (I think) as the mobility scooted was designed to pull 20-22 Stone, him and the jeep will be about half that.
Thanks again

 

[TBirdUK]

luckily I have a variable speed throttle, so will adjust until he gets used to it - he had one, before I ripped all the gear out for another, that was about 6mph so all should be good - I am also going to install a remote 'kill' switch on the power, just in case!