Garmin Varia RearVue 820 review: a genuinely next-gen bike radar

Brand spanking new for 2026, the Varia RearVue 820 has quite the reputation to live up to – its predecessor, the RTL515, was widely lauded as the gold standard among the best bike radar units when it was launched in 2020. So much so, for years, it was the only radar I ever saw, blinking from the seat posts of safety-conscious cyclists.

More recently, other brands began to appear on my radar, encroaching on Garmin’s territory. Garmin’s response? Nada, there wasn’t a hint of a replacement for years. Had it dropped the ball? I began to wonder if it even remembered it was still in the game.

Six years is a long time in tech, but Garmin has redeemed itself. It has prevailed. This new Varia radar punches well beyond an obligatory cosmetic refresh and subtle feature tweak - it genuinely pioneers new levels of accuracy. I was so impressed with it, I awarded it ‘Best on Test’ in Cycling Weekly’s group test of the best bike radars.

If I have a criticism, it’s that ‘Garmin Varia RearVue 820’ is a bit of a mouthful, so from here on in, I will refer to it more plainly as the RearVue 820.

Construction

While the RearVue 820 clearly draws some design cues from the RTL515, Garmin has implemented a fresher, bolder look for this new unit. Gone is the black, slab-like aesthetic; replaced with deeper, bevelled edges, more scarlet-tinted transparent polycarbonate, and better-defined side lenses for improved visibility. The main lens now sits at the bottom, but you can rotate the unit upside-down if you enable this feature in Garmin’s Varia app.

A small, lozenge-shaped power button is located at the top of the unit, beside a tiny status LED. This button looks slightly more robust than previous versions, which, in my experience, were prone to early failure. At the back of the unit is a USB-C (hurrah!) charging socket, protected by a weatherproof flap, which also feels sturdier than the one on the RTL515.

Back in 2020, Micro-USB was already very long in the tooth, but for some reason, Garmin stuck with it for the RTL515, a poor decision that marred an otherwise excellent device. This design ‘faux pas’ really got users’ backs up, including my own. The legislation-mandated switch from Micro-USB has seemingly taken Garmin aeons to implement, but to be fair, the brand is now uncharacteristically well ahead of the curve. Not only does the RearVue 820 feature USB-C, but it also has a replaceable rechargeable battery, ensuring compliance with EU rules coming into force in 2027.

This is a welcome development. For keen cyclists who subject their RearVue 820s to frequent charging cycles each month, or those who reasonably wish to keep an expensive piece of technology operational for as long as possible, the ability to replace the battery is a significant advantage. The battery is accessed by removing the rear cover, which is secured with six teeny Torx bolts. Weatherproofing remains decent, rated IPX7.

Light output has also been increased as part of the upgrade. Compared with the old RTL515, the RearVue 820’s rear light now delivers 100 lumens in day flash, up from 65, and 25 in solid, up from 20. Night flash is also brighter – 40 lumens from 29, and peloton mode, a reduced output to avoid annoying your riding buddies, remains at 8 lumens.

All of these improvements are welcome, but they’re unlikely to blow your UCI regulation socks off. The seismic change is that Garmin has switched from low-resolution 24 GHz radar to significantly more precise 60 GHz waves. In practice, this makes it more responsive, more accurate, and better at tracking vehicles travelling at the same speed as you. In fact, the higher-resolution signal enables it to distinguish between vehicles – trucks, cars, and motorcycles – and display them accordingly. What’s more, with the benefit of a wider 60° sweep, it can identify a vehicle’s lane position on the road.

As you’d expect, the RearVue 820 works in conjunction with Garmin’s own Varia smartphone app, which is available for both Apple iOS and Android, and any contemporary bike computer that supports ANT+ Radar and ANT+ Smart Light protocols. I tested it with a Garmin Edge 1050, a Wahoo Elemnt Roam 3, and a Garmin Forerunner 970 smartwatch.

There is some bad news. Although still widely supported, ANT+ has been deprecated, so support for some of the RearVue 820’s more advanced features is limited. Garmin’s relatively new secure Bluetooth (BLE) protocol is required for lane positioning and vehicle size recognition to work at all, which restricts these standout functions to users of Garmin’s Varia app or its Edge XX40/XX50 head units.

Garmin’s quarter-turn mount has always been a triumph, but the rear ones have typically prioritised function over form – they often looked like an afterthought. The Ethylene Propylene Diene Monomer (EPDM) securing loop (aka, rubber band) was fiddly to adjust, and even when mounted securely, the radar looked precarious. The new design is more attractive, similar to Wahoo’s mount for its Trackr Radar, and the rubber O-ring has morphed into an easier-to-handle, more robust rectangle reinforced with additional material at the centre. There are two bands in the box, of different lengths, along with two rubber bushings for round and aero seat posts. These can be inverted to match various seat post angles – 77°, 73°, and so on. Lastly, a lanyard and tether point are welcome additional features.

The Ride

Like all bike radars, the RearVue 820 requires a paired device mounted at the front of the bike – usually on the handlebars – to relay traffic information to the rider via visual prompts, sound, vibration, or all three. A GPS bike computer is the obvious choice for this task; a compatible smart watch works well, but the low-cost option, if available, is a dedicated smartphone app.

Garmin is one of the few brands that offers a proper, feature-rich companion app, and I’ve always regarded it as an excellent solution. Many of the apps provided by its competitors do little more than let you adjust settings, offering very limited functionality.

Whether you plan to use the app as your primary device with the RearVue 820 or not, it’s still a useful starting point for initial setup. Here, you can easily update its firmware, configure its orientation, and even create custom light modes to supplement the five (including ‘off’) modes it ships with. Want a daytime flash with 80% brightness and a duration of 200ms? You’ve got it. I don’t imagine many users will bother programming custom light modes, but it’s a valuable feature for ultra-endurance riders looking to optimise battery life over long distances.

Using the default settings, all lighting modes, including day flash, are super visible. Even in very bright conditions, the day flash can be spotted a good couple of kilometres away - that's well over a mile.

Essentially, the display page functions like every other radar smartphone app and head unit screen. You and your bike are represented by a fixed icon at the top of the screen, while approaching vehicles appear at the bottom and move upward as they get closer to your position. The rate at which they move depends on their speed. Your speed, the device’s battery level, and light mode are also displayed.

However, while other radars display vehicles with generic car icons (Wahoo) or simple dots (previous Garmin units), the RearVue 820 shows a long rectangular icon for large trucks, a shorter icon for cars or small vans, and a narrow icon for motorcycles and bicycles. Their lane position is also indicated, helping the rider to better judge the relative risk they pose. Threat level, determined by vehicle size, speed, and lateral distance from your path, is shown by a warning triangle superimposed on each vehicle icon plus a shaded halo beneath it. These are coloured orange for a mid-level threat and red for a high-level threat.

The display on a modern Garmin XX40/XX50 series head unit is very similar, with the option to show a dedicated Radar Data Screen or a column overlaid on the side of an existing data screen. This overlay can be positioned on the right or left, and there are two column widths to choose from, large or small. Selecting the smaller width makes it easier to see the underlying data screens, but it becomes harder to gauge traffic approaching from behind. Optionally, the overlay can be set to display orange, red, and green colours to indicate when a threat is detected, the severity of the threat, and when the threat has passed.

Both the smartphone app and the head unit will emit sounds when a threat is detected and cleared. These can be customised or, if you prefer, muted. Additionally, a smartwatch, such as my Garmin Forerunner 970, will vibrate on detection. It is possible to pair the RearVue 820 with both a head unit and a watch at the same time, giving you the best of both worlds – useful on noisy, traffic-heavy routes. Similarly, it’s possible to pair a head unit and the smartphone app, enabling you to listen to the tones through bone-conducting headphones.

To test the effectiveness of the RearVue 820, I rode a predefined 13km circuit that ensured a variety of traffic conditions and numerous reflections from buildings and structures likely to confuse a bike radar. I also set up a static rig on a long, straight stretch of road, allowing me to accurately test range and log false positives and negatives with confidence. The RearVue 820 also accompanied me on my regular rides throughout January and February.

On the road, I found that riding with the RearVue 820 is like switching from a grubby pair of glasses to a fresh, clear pair. Thanks to the higher resolution, much more detail is visible; the range has increased – regularly exceeding 160 metres during my static test, even for smaller cars – and the RearVue 820’s ability to distinguish individual vehicles within a group has improved. Vehicles travelling at the same speed as me are tracked with greater persistence, rarely dropping out at slow-moving roundabouts or at the approach to road junctions.

Less convincing is its ability to classify vehicles by size. Knowing whether you’re being followed by a truck, a car, or a motorbike is an appealing idea, but in practice, it's not yet fully reliable. I did find that very large vehicles were often identified correctly, which is a positive, as being forewarned enabled me to prepare for the strong air currents that accompany a swift overtake.

However, cars shown on my head unit would occasionally turn into motorcycles and vice versa. I wish the unit could better distinguish motorcycles and bicycles from other vehicles because, riding on my narrow Cotswold lanes, I often pull over only to find it’s just another cyclist spinning past rather than a car. Hopefully, future firmware updates will improve its accuracy.

On a more positive note, I found that lane detection worked very well, enhancing my situational awareness in complex major road systems and urban areas.

On the face of it, the additional traffic information provided by the RearVue 820 marks a significant advancement for bike radar. Ironically, my only concern is that sometimes it can be a bit overwhelming. A large part of my time in the saddle is spent looking ahead or scanning left and right for hazards. I rarely look down at my head unit. Even when I do, I give it a quick glance, and only after an audio alert tone prompts me to do so. In that fleeting moment, I have just enough time to gauge the approximate position of the threat relative to mine, which is enough. Trying to identify exactly what type of vehicle it is, or pinpoint its exact position on the road, feels like it’s demanding more of my focus than is warranted.

Off the bike, battery life is exceptional – I achieved an impressive 11 hours 15 minutes in solid light mode, and Garmin reckons it’s good for 24 hours in day flash mode, which I can well believe. Charging time is roughly two and a half hours from empty to full.

Finally, a quick note about the mount. It’s a small detail, but the new rubber strap is an improvement over the old one; it’s now easier to attach the mount to any seat tube. The action of the quarter-turn action remains, without doubt, class-leading.

Value and conclusions

With an RRP of £259.99/$299.99, the Garmin Varia RearVue 820 is very expensive. You’re paying a £100/$100 premium over the street price not only for the somewhat outdated Garmin Varia RTL515 but also for Wahoo’s Trackr Radar and Lezyne’s Rear Drive 300. All excellent products.

However, in terms of accuracy, the RearVue 820 is unrivalled. Even after testing the unit for several months, I’m not entirely convinced that I need the level of traffic information it can provide, but I am captivated by the precision it offers and the persistence with which it tracks vehicles.

Can you get away with using the cheaper Wahoo or Lezyne radars? Yes, absolutely. Both outperform the old RTL515 that I’ve been happily using for years. Nevertheless, if you can afford it, you’ll find the RearVue 820 next level.

Specs

• Dimensions: 98.9 x 25.9 x 43.2 mm (3.9” x 1” x 1.7")
• Weight: 90 g (3.2 oz)
• Light modes: solid, peloton, night flash, day flash
• Custom light mode configuration: Yes (with Varia Mobile App)
• Radar-only mode: Yes
• Lumens: 25 solid, 8 peloton, 40 night flash, 100 day flash
• Water rating: IPX7
• Battery life: 10 hours solid, 15 hours peloton, 10 hours night flash, 24 hours day flash, 30 hours radar-only
• Ant+®: Yes (radar, bike lights)
• BLE: Yes (radar, bike lights)
• Viewing angle: 220°
• Visibility distance: 2 km
• Rear tail light: Yes
• Brake light: Yes
• Rear radar: Yes
• Lateral vehicle positioning: Yes
• Vehicle size classification: Yes
• Vehicle threat classification: Speed-, size- and lateral range-based
• Maximum vehicle detection range: 175 m
• Radar beam width: 60°
• Companion app: Varia Mobile App for iOS and Android