My wife and I bought a treadmill before Christmas of last year. It has been great to be able to run regardless of the weather or daylight this winter. A couple of days ago the weather was warm so I headed outside for the first time in a while. I was running on a known course – the arboretum at UK - and realize that I seemed to be running at a faster pace based on perceived effort compared to my perceived treadmill effort. If anything, it should be the other way around. My guess was that the treadmill was reporting a slower speed than it was actually moving at. But how do you calibrate a treadmill? The manual gave a procedure for calibration that allowed the roller diameter to be adjusted prior to running through an automatic calibration procedure. So here’s how I did it.
I have a bicycle, a wind trainer (rear wheel clamp style), and a bike computer (speedometer). The following could be done without a wind trainer, but it makes the whole thing a lot easier. My particular computer (Cateye Astrale 8) uses a rear wheel speed sensor. I made sure the bike computer was properly configured with the wheel circumference. I then clamped the rear wheel in the wind trainer as per normal use and positioned the bike such that the front wheel was on the treadmill belt as if I were going to ride the bike on the treadmill. Next I moved the trainer forward on the floor behind the treadmill until the rear wheel made contact with the belt. I checked that there were no obstructions then turned on the treadmill at its slowest speed. As the belt moved it turned the wheels showing the speed of the belt. I tested the treadmill at six, eight, and ten miles per hour and found it to be moving about 0.2 mph fast. That is, when the treadmill said eight mph the bike computer said 8.2 mph.
From here on it was just a slow process of trail and error. I went through the set up procedure for calibrating the treadmill, each time increasing the setting for the size of the rollers by a couple of points. I finally arrived at a setting of 2.89 as opposed to the setting of 2.81 listed in the manual. Once the speeds agreed I let the whole setup run for a few miles to see if the distances would match up as well. A small difference in speed between the treadmill and bike computer – both of which only read to a tenth of a mile per hour – would easily show up over a distance of a few miles. Overall I found the two to match up well with the treadmill running perhaps .05 mph faster, which is fine for me.