The CarBack comes with a rubber band for attaching to your seat post. However, as two of my bikes have aero seat posts, it didn’t sit perfectly. This meant the light kept shifting to one side of my seat post and was not facing straight behind my bike. It also caught on my thighs a few times. It did fit better on my gravel bike with its more traditional seat post, so this could be something to keep in mind.

Of course, Trek designed this light for their bike models, which have the ability to mount the light on the back of the saddle. This would eliminate the above issues.

Once on the bike, as cars approached, that familiar beep was back. Along with the audio cue was the visual display on my Wahoo—the green bar changing to red, indicating if one or more cars were approaching. The closer the car was to the top of the red bar, the closer it was to me. When the car or cars passed, the bar returned to green, and another distinctive beep sounded to let me know all vehicles had cleared.

I personally like both these indicators; however, you can switch off either to have just audio or just visual alerts. I felt the CarBack was on par with detecting cars—when riding with my partner, both beeps sounded simultaneously or within a second of each other. The detection is accurate, though I did notice on a couple of rides that cars were quite close before being detected. This seemed to coincide with twisting roads, leading me to believe that bends in the road affected the CarBack’s ability to detect vehicles at the advertised 240m range.

The battery life seems great. The reported run time is 7+ hours, regardless of light mode. My longest ride in December was five hours, and the battery held up throughout. I also particularly like that the battery life is easily visible on the side of the unit while riding.