The radar video that started it for us
You should be riding with a rear radar. We said it in 2020 and we still say it. If you are shopping today, start with the Garmin Varia RearVue 820, then read our newer comparisons below.
We posted this video to YouTube in October 2020. We unboxed the Varia RTL515, went through the specs, talked about how we use it, and ran through our top five reasons to consider one. The line from that description still sums it up for us: we feel like we are riding naked when we are not using radar.
What the RTL515 does
You probably know the moment: you are riding a quiet road, you hear a motor somewhere behind you, and you turn to look. Your shoulder turns, your bars follow, and the bike drifts toward the lane you were trying to stay out of.
A rear radar takes that look off your list. The RTL515 sits on your seatpost as a tail light and watches the road behind you. When a vehicle comes up from behind, it tells your head unit, so you can keep your eyes forward and your line straight.
What Garmin rates the RTL515 for
- Range
- 140 m
- How far back the RTL515 detects approaching vehicles
- Battery
- 16 hr
- RTL515 battery in day flash mode. Solid and night flash are rated at 6 hours.
- Vehicles
- 8
- Approaching vehicles the RTL515 can track at once
Source: Garmin's Varia RTL515 owner's manual.
Garmin's manual lists a 40 degree beam, which it says covers typical bends in the road, and vehicle speeds from 10 to 160 km/h (6 to 99 mph). The light puts out 65 lumens in day flash, and Garmin says it is visible in daylight from up to a mile. It is rated IPX7 for water.
It does not see a car going your speed.Garmin's RTL515 manual says so plainly, and newer Varia radars changed that.
The short answer in 2026
As of October 2026, Garmin still lists the RTL515 on its US site, but we no longer stock it. The radars we carry now are the Varia RearVue 820, the camera equipped Varia RCT715, and the Wahoo TRACKR Radar.
The biggest change since this video is the RearVue 820, which Garmin announced in February 2026. Garmin rates it to see farther back than the RTL515 and says it alerts you to a vehicle that sits behind you at your speed, the exact case the RTL515 manual says it misses. We broke the newer lineup down in the two posts below.
- RearVue 820 vs RCT715: the stronger radar and light against the one with a camera, from a lab that has lived with the camera.
- RearVue 820 vs Wahoo TRACKR: range, light, battery, fit, and what happens if your only screen is your phone.
- Edge 550 vs 850 vs 1060: if you still need a head unit to pair it with.
The video is from 2020. The specs in it describe the RTL515, not what we would buy today.
The reason to ride with radar has not moved. It means fewer looks over the shoulder, a straighter line, and no surprises from behind.
Radar tells you what is coming, but you still decide what to do about it.
Common questions
How far can the Garmin Varia RTL515 see?
Garmin's manual says the RTL515 detects approaching vehicles up to 140 meters away with a 40 degree beam, at vehicle speeds from 10 to 160 km/h.
How long does the Varia RTL515 battery last?
Garmin rates it for up to 16 hours in day flash, 8 hours in peloton mode, and 6 hours in solid or night flash.
Does the RTL515 detect cars going the same speed as me?
No, Garmin's RTL515 manual says the radar does not detect vehicles traveling at the same speed as your bike. Garmin says the newer Varia RearVue 820 does alert you to them.
Which Garmin radar should I buy now?
For most riders we recommend the Varia RearVue 820. If you want video of the road behind you, look at the Varia RCT715. Our comparison posts cover the details.
Ready to add radar?
Every radar we carry is on one page, and we ship nationwide. Questions about which radar works with your bike computer? Ask us.
Shop lights and radarKeeping your eyes on the road ahead was always the point.