Portland Design Works' Gravity Plus Tail Light has a built-in accelerometer that detects deceleration or swerving and automatically changes to a super bright, solid beam to warn following traffic. To allow the accelerometer to calibrate, always install the Gravity Plus on your bike before powering it on. Hold the power button down for 1 second to turn the light on or off. Then, keep your bike still for 1 second after pressing the power button to complete the calibration.
The Gravity Plus Tail Light has redesigned mount that works with the included seatpost and seatstay brackets.
- Automatic accelerometer brake light function shines 100 lumens bright.
- USB rechargeable li-polymer battery.
- Weatherproof exterior for all season riding.
- Mounts vertically or horizontally.
- 2 Modes (runtime): Solid - 20 lumens (12 hours), Flash - 80 lumens (30 hours).
- Weight: 1.9 oz.
- Includes brackets for seatpost and seatstay mounting and Micro USB Recharging Cable.
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I was initially very excited about this light to use when my wife and I are riding together to help us signal to whichever one of us is behind that the one of us in front is slowing down. However, we discovered that on anything but super smooth, flat roads the light went into the super bright warning mode extremely frequently. After a few rides, one of the two lights pretty much stays in this mode constantly and eats up its battery in the process. I have given up on these lights and bought different lights instead.
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