It is easier then you think.
Splicing bike computer wiring together to make it longer so the sensor can be put on the rear wheel that is. I just got done doing just that. Why would I want my sensor on the rear wheel, especially after having it on the front all spring & summer long? Well so I can continue to keep track of my mileage even while riding on my trainer.
I had the wiring from a couple of old computer sensors. The computers bit the dust long ago. Guess it's a good thing I kept the mount, wiring & sensor huh?
All I did is cut & strip the wiring, twisted it together, covered/sealed it with electrical tape & voila! A longer bike computer wiring with mount & sensor.
One thing I did have to do though is use spacers to move the sensor closer to the magnet attached to the spoke. The reason is on my bike, (a Vision R40), the chain stay & rear spokes is quite a distance apart. I simply wrapped an old inner tube around the chan stay until the sensor was close enough to the magnet so the signal could be picked up & transmitted. It may not look pretty but it is functional & works well.
For those that want to keep track of mileage while using a trainer this is an effective means of doing so if you ride a recumbent.
One thing to not forget though is be sure you also change the setting on your computer for the differant wheel size.
Most cycle computers use a reed switch to sense the magnet, the switch is an open
circuit until near the magnet when it closes. The computer debounces the switch closure and counts closures per time interval and calculates the result. The wire is stranded 24g and easily spliced, though I would use a more positive mechanical bond
than twisting, and soldering would be best. If you listen carefully as the switch goes by the magnet you may hear the soft click-click as the switch closes and opens again. Steve