Of all the various computers that I've had on bikes, I don't recall ever reading instructions regarding placing the magnet closer to the hub.The max distance from the transmitter to the receiver is specified because the tranmitter is low power. If you think about it, at any given wheel rotation speed, the magnet spends the same time in front of the transmitter. The speed you're referring to I believe has to do with centrifical force, not elapsed time in front of a stationary object.