Easy install with a similar mounting bracket to the Garmin Edge computers with a beefed up mount.​

What is it

It's a seatpost mounted radar and light that provides visible and audible alerts for vehicles approaching from behind up to 153 yards (140 meters) away. It's also a smart, integrated tail light is visible in daylight from up to a mile away and integrates with most Garmin cycling head units.



  • Provides visual and audible alerts warning rider of vehicles approaching from behind.
  • Daylight visibility up to a mile away and is visible within a 220-degree range.
  • Easily mounts to most seat post styles including traditional round and aero style.
  • Long battery life-15 hours in flashing mode or 6 hours in solid or night flash mode.


  • Requires a dedicated radar display unit when not using compatible Garmin devices.
  • Lumen output is low on the unit and could be brighter for dusk visibility.
  • Must purchase aftermarket mounts if you intend to use on multiple bikes.
  • Light unit is quite big
  • $200 is pricey just for the light unit

The Varia has 220 degrees of light to make sure overtaking vehicles see you no matter what.​

RoadBikeReview's Take

As cyclists we try and keep our ears tuned for the sound of car engines, buses, often warning others with "car-back!" But what happens when you hear the car is coming too late? We've all unfortunately been buzzed by a car that we didn't know was coming. Whether the wind drowned out the engine or you plain didn't hear it riding on the road can be dangerous. Any tools that can help lower the situations where we put our lives at risk is worth a look.

Enter the Varia Radar system by Garmin, a seatpost mounted radar and light that provides visible and audible alerts to riders. The Varia RTL510 is the newest iteration of the Garmin rear-mounted radar systems. It takes the past Varia and updates the unit shape, mount and output all around, making it easier to use and integrate into your daily cycling routine.

Once the Varia unit is paired and working a small sliver of the Garmin 520 display is used for radar and detection.​

The Varia RTL510 is designed to detect vehicles approaching you from behind, equipped with a rear-mounted light that approaching vehicles can see from the back and side. The Varia RTL510 is available in two forms, the rear radar unit by itself for $200 or a bundle with the rear unit and with a small handlebar mounted display for $300. Both are effective in alerts and display for overtaking vehicles and when the coast is clear. The primary function is safety and helping riders know when vehicles are coming and how fast. The way the Varia alerts the rider either through a users Garmin compatible device (510-520, etc.) or through the head unit that is available in the Varia bundle. The unit displays overtaking vehicles via dots on the screen, detects how fast they are approaching, and how far away they are. The unit also lets the user know if multiple vehicles are coming with more dots on the screen clustered together. The rear-mounted light also flickers faster at this time, giving an extra bit of alert to the driver that you are indeed there.

The Garmin Varia RTL510 cycling light and radar, peace of mind in a small package.​

The install and pairing of the device with the Garmin Edge 520 are just like setting up any other sensor; search-pair-done. Once the unit is paired and working, a small sliver of the display is used for radar and detection, taking nothing away from the original display or size of the output. Mounting the unit to the seat post is simple and works well with traditional round and aero designs. I like that the bulk of the unit is under the seat post clamp, giving the user ample room for a saddle bag and other accessories if needed.

When in action the Varia gives an audible but not intrusive beep that alerts of car approaching, as well as displaying a small dot on the screen to help the rider plan action. The dots that show on the head unit travel at speed the Varia detects and moves along the display until the vehicle has overtaken the rider. The most useful moments for the Varia are when pedaling, buried in the drops with a headwind dulling the senses. I had several instances where I had to double check the radar's beeping as I was sure there was no car approaching. But there was indeed a vehicle. Working seamlessly with the Garmin suite the Varia will even send "Low-Battery" messages to the head unit when it needs some juice. Garmin says the battery life is 15 hours on flashing mode, but I've yet to run out entirely, as the Varia charges very quickly.

As the light goes, it's effective in all daylight situations but could be brighter for dusk and sundown riding. The battery breakdown is 6 hours solid at 20 lumens, 6 hours night flash at 29 lumens, and 15 hours day flash 69 lumens.

So if you cover the Varia in mud, it won't work, but expected from a radar (insert radar jammed joke from Space Balls).​

Though the Varia works very well on the road, I find that mud and grit from gravel and "single track detours" make the radar less sensitive and sometimes ineffective. So if you cover the Varia in mud, it won't work, but that is expected from a radar (insert radar jammed joke from Space Balls).

The more and more I ride with the Varia the more I think the unit is a must have for triathletes and time trialists, the piece of mind and accuracy is worth the price of admission alone.

Varia RTL510 Radar Tail (tested) $200.00
RTL510 Light and head unit bundle $300.00

Rating: 4.0 out of 5
More Info: Garmin site