I use wireless odometers (the cheaper ones). They're prone to interference. Every now and then my top speed would read over 75MPH. Once, while setting one up, I was watching TV and when I hit the TV remote, it said I was doing about 25MPH on my sofa. Also, I bought battery operated heated gloves for the winter. If I put them on low or medium, it throws off the readings on my odometer. The high setting is fine. These quirks vary from manufacturer. I've probably used 10-12 different brands/models over the years.