Bontrager Flare RT Rear Light
The Bontrager Flare RT is our most visible rechargeable rear bike light, engineered to keep you seen in any condition. With 90 lumens of output and precision-focused optics, the Flare RT projects a beam pattern visible from over 2 kilometers away in broad daylight. We designed this light for riders who demand reliability — whether you're commuting in morning traffic or training through dusk.
Our Flare RT features five flash modes plus a steady beam option, giving you the right visibility for every ride. The integrated USB rechargeable battery delivers up to 15 hours of runtime on flash mode, and our low-battery indicator ensures you're never caught off guard. The secure two-bolt mount fits most seatposts and stays locked in place over rough terrain.
Light output & visibility specs
Focused optics for maximum visibility
The Bontrager Flare RT uses a patent-pending optical design that distributes light horizontally across a 270-degree field. Unlike traditional round-beam taillights, our focused optics concentrate lumens where drivers actually look — creating a wider, more attention-grabbing profile from the side angles that matter most at intersections and roundabouts.
This optical system delivers more visible lumens per watt than standard LED arrays. Independent testing shows the Flare RT registers visible from 2 kilometers in full daylight, making it one of the most effective rear lights for daytime commuting. The polycarbonate lens is scratch-resistant and transmits 92% of the LED output without diffusion loss.
Battery life and charging
We equipped the Flare RT with a 500mAh lithium-ion battery that recharges via micro-USB in just 3 hours. Runtime varies by mode — you’ll get 15 hours in day flash, 6 hours in night flash, and 5 hours on steady high beam. Our three-LED fuel gauge shows real-time battery status, with amber and red warnings before you run out.
The battery management system protects against overcharge and extends cell lifespan to over 500 charge cycles. We designed the USB port cover to seal completely — the Flare RT maintains IPX7 waterproofing even when charging in wet conditions. The light remembers your last-used mode and brightness setting between rides.
Mounting and compatibility
Our two-bolt Blendr-compatible mount locks onto round seatposts from 25.4mm to 31.8mm and fits most aero profiles without adapters. The mount’s rubber strap hooks into molded channels for tool-free installation, and the secondary retention bolt prevents rotation even on bumpy gravel descents. You can remove the light body with one hand while leaving the mount in place.
The Flare RT also pairs with ANT+ bike computers for wireless control and low-battery alerts. When connected to compatible Garmin or Wahoo devices, you can toggle modes without reaching back. The mount sits low enough to avoid interference with saddle bags, and our optional bike light accessories include helmet mounts and rack adapters for versatile positioning.
Complete your visibility setup
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Flare RT rider questions
The Flare RT delivers higher daytime visibility than most competitors due to our focused optics, which concentrate lumens horizontally rather than dispersing them in all directions. At 90 lumens, it's brighter than many rechargeable taillights in the same price range, and our optical design means more of that output reaches drivers' eyes.
The combination of long battery life (15 hours on day flash), ANT+ connectivity, and IPX7 waterproofing makes it competitive with lights that cost significantly more. We back the Flare RT with a two-year warranty covering defects in materials and workmanship.
Yes, the Bontrager Flare RT includes both high (90 lumens) and low (30 lumens) steady beam options. Some cities and group rides prohibit or discourage flashing taillights, so we designed steady modes that provide continuous visibility without the strobe effect.
Steady high mode is ideal for well-lit urban areas where you need constant presence, and steady low extends your runtime to 11 hours while maintaining enough brightness for traffic awareness. You can toggle between modes by pressing the power button.
Our two-bolt mount fits round seatposts from 25.4mm to 31.8mm in diameter without additional adapters. It also accommodates most aero and D-shaped seatposts commonly found on road and gravel bikes.
The rubber mounting strap stretches to fit oversized posts, and the secondary bolt prevents the light from rotating on carbon or slippery aluminum surfaces. If you have an unusual seatpost profile, we offer optional adapter shims on our accessories page.
The Flare RT features a three-LED fuel gauge on the top of the light body. Green indicates a full charge, amber shows medium battery, and red alerts you when power is below 20 percent. The gauge is visible while riding, so you can check battery status at a glance.
If you're paired with an ANT+ bike computer, you'll also receive low-battery alerts on your head unit. We recommend charging when you see the amber indicator to ensure you have enough runtime for your next long ride.
Yes, the Bontrager Flare RT is rated IPX7, meaning it can withstand submersion in 1 meter of water for 30 minutes. We use ultrasonic welding to seal the housing and a double-lip gasket on the USB port, so rain and road spray won't penetrate the electronics.
We've tested the Flare RT in sustained heavy rain, creek crossings, and pressure washing without water intrusion. The USB port cover seals completely even when you're charging the light in wet conditions, making it reliable for commuters and all-weather riders.
Yes, the Flare RT includes ANT+ wireless connectivity that pairs with compatible Garmin, Wahoo, and other ANT+ bike computers. Once paired, you can toggle between flash modes, check battery status, and receive low-battery warnings directly on your head unit.
You can also add the optional Bontrager Transmitr handlebar remote for one-button mode switching without reaching back. This is especially useful for switching from day to night flash as lighting conditions change during long rides.
Your Flare RT package includes the light body, two-bolt seatpost mount with rubber strap, micro-USB charging cable, and quick-start guide. The mount attaches tool-free in under a minute, and the light slides into the mount with a secure locking mechanism.
We don't include a wall adapter — you can charge via any USB port on computers, power banks, or standard phone chargers. Optional helmet mounts and rack adapters are sold separately if you need alternative mounting positions.