Top 100 Contributor
If the 2 sensors are too far from each other then they cant detect each other but it doesn't matter where on the wheel you put it. The sensor on the bike doesn't need to be near the rim of the tyre and it is alright to put the sensor on the wheel somewhere were it will fit. The computer counts the number of times the wheel turns around and then works out what speed you are going from that. If you think about it if it was worked out by the number of times the sensor went past the bike sensor it would not be able to tell if you was going fast or slow.