Short and sweet.
The Duotrap is a combined speed/cadence sensor, designed to work with compatible Trek bikes. It mounts in the non-drive side (left side) chain stay.
The little black dot in the middle of the duotrap is a rubber cover over an allen screw that holds it firmly affixed into place.
The duotrap goes through the chainstay, and protrudes with its speed receiver on the inside:
There the traditional wheel-mounted magnet, and there is also a magnet in a heavy-duty rubberband that goes on your crank arm.
Unless you’re really looking, it blends right into the bike.
Install takes all of a minute. Slide the rubberband over the crank arm, pop off the cover on the frame, pop in the Duotrap, and screw it down.
Actually, I take that back–there is one key step missing there. Here’s my little, whiny criticism: Bontrager doesn’t include a battery with the Duotrap. So you buy an expensive Trek bike that is compatible, spring for the Duotrap, and then have to track down a battery separately. Fortunately, my Local Bike Shop was prepared for this predicament, and had the batteries close at hand.
I use a Garmin 800 that is ANT+ compatible. The Duotrap is also ANT+ compatible. Pairing the Duotrap and the 800 was dead simple. Set the Garmin to pair mode, and spin the cranks a bit. It paired perfectly, and has been dead reliable for the couple weeks that I’ve been riding Max.
The instructions do not give much detail about magnet placement on the wheel. I can say that, because of the distance between the magnet and sensor (the sensor is nonadjustable), it was a bit finicky at first. I’ve found that ideal magnet placement is towards the rear edge of the sensor. If the magnet lines up with the back end of the sensor, it’ll be about perfect.
The sensor transmits both cadence and speed, and works very functionally. For Max, the form and function are both greatly appreciated. By way of comparison, on the Ridley, I used Garmin’s combined cadence/speed sensor, zip-tied to the chainstay:
The Garmin unit is a perfectly functional setup, but it’s ugly (look on the far chainstay, just behind the wheel). Separately…I use that setup on the Vaya, and have had problems with it. On the Vaya, with relatively round chainstays, the Garmin speed/cadence sensor can get jostled around…which can result in it going into the wheel in extreme conditions. That’s a pain in the butt…and potentially a bit dangerous. Duotrap avoids those issues.
The Duotrap makes sense on road bikes…but I think the real market for a product like this is cross bikes and XC mountain bikes. As gravel riding continues to grow and as gravel/cross/mountain riders expand their use of data (power, cadence, speed) for their training regimens, it only makes sense. Perhaps a more waterproof’d verson of the Duotrap, and compatible mountain/cross gravel frames? Ya listening, Trek?