Making Your Bike Speedometer Work With a Bike Trainer

The directions for bicycle speedometers say to attach the sensor to your front tire. When you use a bicycle trainer (like the CycleOps Trainer I reviewed last week), the front tire remains stationary and the only tire that is moving is the back tire. Is it possible to attach the sensor to the back tire? Does it affect the mileage calculation?

If your back tire is the same size as your front tire (most are), then you won’t have to reprogram your speedometer. If you just bought your speedometer, then you’ll have to program it using the size of your back wheel. The Bell Spinfit Calorie Speedometer, which is the speedometer I have on my bike, has plenty of wire to reach the back tire. Attaching it to the back tire was actually easier for me than attaching it to the front because I didn’t need to figure out what to do with all the extra cord.

The biggest problem with attaching the sensor to the back tire is that the frame is further from the spokes on the back tire. The Bell Speedometer didn’t have a problem with that and I was able to position the sensor so that it was close enough to the magnet on the spokes. Other brands might need some help with this matter. One way of bringing the sensor closer would be to wrap electricians tape or duct tape around the frame until the sensor was close enough to the spokes. This might interfere with removing the back tire, so if you have to do that often, take that into account. As it was, I was able to attach it quite easily using cable ties (the bright green bands pictured here).

Ironically, a workout on an indoor trainer is a lot harder than one outside in the real world, so the eight and a half miles I did on my last workout felt so intense that I couldn’t believe that I only went eight miles. It’s not a problem with the speedometer, however, the resistance is just so much that I get an incredible workout. It feels like I’m going uphill the entire time.

The entire process of changing my speedometer from my front tire to my back tire took a total of about five minutes. The hardest part was getting past my fear of putting it on the back tire. I thought that if the sensor was meant to be put on the back tire, then they would have given alternate directions for it. As far as I can tell, as long as the sensor can reach the magnet on the spoke, there is no problem with putting it on the back tire instead of the front. The best part is that I get a measurement of my workouts in something more than time.