Garmin  Varia RearVue 820 Radar Taillight

After having used the RTL510 for several years, for me, the 820 offers a few significant improvements. The biggest, and only downside of the 510 (and the 515 supposedly had the same issue), is that you can very often get a false negative when a car catches up to you, and then paces you at your speed. By that I mean that the car will show up on your head unit when it is going faster than you, and then disappear when it slows to match your speed. Knowing this downside, when a car catches up to you and then drops off, you can't tell whether the car turned off the road, or is still there. With the 820, it somehow knows that the car is still there, matching your speed so the car doesn't disappear off your screen. This is a huge benefit, because now when the car disappears off the screen, you know it turned off the road. some other improvements are: much longer battery life; the ability to see which lane a car is in behind you; and it gives an indication of the relative size of the vehicle(s) behind you.

For the life of me, I don’t know where these hypocritical reviews come from. I’ve raced criterium for 10 years, have transitioned more to bike packing recently, and ride about 6000 miles a year. I found this light to be about 95% reliable with the traffic that passes me, the number of vehicles it’s identified and the speed with which they are arriving. Updating the firmware through Garmin’s iOS app was seamless. And you have the ability to set up custom light patterns. This process was very easy to understand and upload to the light. The light is very bright, and you will be seen in the daytime from a long ways off. I’ve chosen a GoPro to Garmin adapter. This makes the mounting almost seamless behind my saddlebag. I don’t have any reservations about recommending the purchase of this product even at its full retail price.

I have too many Garmin products :-) and love most of them. I get this Varia update for the battery life. When paired with my head unit In Peloton mode it will stay lit up, alerting you, and not differentiating cars passing. Makes you start to not pay attention to it which is a very bad thing. Garmin has been alerted and many frustrated users on Garmin forums have waited a long time for no update, never mind a fix. I would check forums (“permanent false positive”) before purchasing.

I’ve been buying Garmin products for years. This one is a disappointment. The light isn’t bright enough, and the unit is far too big. And pretty expensive. If you’re small like me, and don’t have a 12” exposed seat post, this device will not fit.

This isn't an upgrade over the RTL515 with the exception of the battery life and usb-c. The tech has gotten worse. It tries to keep you aware of cars behind you that are not approaching at speed. The end result was that it told me my riding partners were cars pacing me. I returned it and went back to my RTL515. It works, so giving it 2 stars instead of 1.

Picks up cyclist as cars quite often, very annoying to use in a group setting. Does pickup cars as well.

Incompetent buggy firmware completely ruins this product. Constant “Radar Fault” errors. Shows as connected, but does not connect properly to my Garmin Edge 1050, where the only indicator that something is wrong is complete failure to alert after being surprised by passing vehicles. DO NOT BUY!

I really love my new Varia 820. Usb-c longer battery life and more accuracy and data . Highly recommend. Read this review https://youtu.be/AHjDw6Vsyvs?is=DJBrgkDNNkHrD8RU. For even more info

Excellent. Completely resolves car anxiety when riding. Tracking is accurate and same speed tracking is a game changer. Glad I got this model over the 515.