Garmin’s New Varia RearVue 820 In-Depth Review: Worth the upgrade?

After nearly 6 years, we finally get a new Garmin radar, the Varia RearVue 820, which brings with a host of new features…and USB-C. Finally, USB-C to their base radar (only their camera edition had it previously). The new unit increases vehicle detection claims to 170m, though far higher in real life, and increases battery claims life to upwards of 30 hours (depending on mode). Did I mention USB-C? It also adds a brake light, adds steady-state traffic tracking, and lets you see the size of vehicles (e.g. truck vs moto). Further, you can also adjust exact blink patterns and brightness, as well as it having a brighter light than previously (visible up to 2km/1.24mi vs the 1.61km/1mi previously).

Of course, with all these new features comes a new price – $299 (compared to the existing $199…though really $149 most of the time). That said, Wahoo’s new radar is also in roughly the same ballpark at $249, though the new Lezyne radar is less expensive at $179. But more on some of those quick comparisons a bit later.

And more importantly than all that: Does it actually work? Are these new features useful, or just a marketing gimmick? As you’ll see, the answer is mixed. There’s a lot of good here, but also some minor fires to address too.

Lastly, this is a media loaner from Garmin. I’ve already ordered my own unit at regular price, for long-term usage purposes.  As always, I don’t accept advertising from any company I review, and no company sees my reviews before you do. So, if you found this review useful, consider becoming a DCR Supporter, which gets you an ad-free site, plus the behind-the-scenes video series between both myself (and my wife) on everything that happens in the DCR Sports Tech Cave/universe.

What’s New:

Here’s everything that’s changed compared to the existing RTL-515 that so many of you have:

– Added/switched to USB-C (from MicroUSB)
– Increased battery life from 16 hours to 24/30 hours (24 hours with day flash, 30 hours radar only, see battery chart below)
– Increased vehicle detection range to 170m from 140m
– Increased brake light visibility to 2km/1.24mi, from 1.61km/1mi previously
– Increased radar beam width (from 45 degrees to 60 degrees)
– Added brake light function
– Added vehicle size tracking (e.g. car, truck/bus, bike)
– Added vehicle position tracking (e.g. which lane)
– Added light pattern customization and light intensity customization (create your own)
– Added new radar-only mode (no light)
– Added secure Bluetooth pairing option
– Added new radar data field option (uses full side column)
– Added same-speed vehicle tracking (even same-speed bike tracking, in a group)
– Added ability to configure orientation, mounting it either direction (or have it auto-detect, by default)
– Added ability to user-replace the internal battery (designed for battery end of life, not daily usage)
– Changed from 2.4Ghz & 24Ghz frequencies to ~2400Mhz & 57-69Ghz ranges
– Increased weight (from 71g to 90g)
– Similar height dimensions, but a bit thicker (98.9 x 25.9 x 43.2mm vs RTL-515at 98.6 x 19.7 x 39.6mm)
– Light lumens all increased (see chart below), except peloton mode, which you want to stay the same
– Slight decrease in minimum operating temp from -20*c/-4*f to -15*c/5*F. Max operating temp remains 50*c/122*f
– Increased price from $199 to $299

From a battery standpoint, here’s the specific claims:

– 10 hours solid (was 6hrs)
– 15 hours peloton (was 8hrs)
– 11 hours night flash (was 6hrs)
– 24 hours day flash (was 16hrs)
– 30 hours radar-only tail-light off (no previous battery spec/claim)

Next, from a light standpoint, the changes are:

From a battery standpoint, here’s the specific claims:

– Solid: 25 lumens (was 20 lumens)
– Peloton: 8 lumens (was 8 lumens, you want this to stay the same)
– Night flash: 40 lumens (was 29 lumens)
– Day flash: 100 lumens (was 65 lumens)

On the whole, these changes essentially make it the most ‘powerful’ cycling radar out there (in terms of detection distance, visibility, battery life, etc), with by far the most features. Keeping in mind, it still retains:

– ANT+ connectivity (with ANT+ Radar standard, and ANT+ light standard)
– Bluetooth Smart connection for 3rd party apps
– Smartphone app for displaying vehicles and alerts with free Garmin Varia app
– IPX7 water resistance (30 minutes at 1-meter deep, in the event you really effed up on your ride)
– Solid light mode, night flash, day flash, and peloton light mode
– Firmware update capability

Got all that? Good. The unit will start shipping this Friday, February 6th.

In the Box:

Here’s the box above, and everything that’s in the box below.

There’s a slightly redesigned seat post mount (the connector to the radar remains the same, though), which includes a d-style seat post mount, a rounded seat post mount, and an aero seatpost mount. All of which connect to the plastic piece at right.

From there, you use the now double-wide rubber band to attach it to your seat post. They also toss. In a tether, just in case. See that, Garmin inReach Team? A $299 product can indeed include a tether…

Here’s the front side, complete with a sticker, along with the backside.

Here’s a look at how this unit compares in size to that of the existing Garmin Varia RTL-515 radar, the Wahoo TRACKR Radar, and the Lezyne Radar Drive. They each have their differences, though on the whole they’re kinda similar honestly. I think Wahoo has the cleanest looking design, though of course Garmin bulks up on size to translate to battery (and better accuracy/reliability).

Here’s another angle (note the two Garmin radars switched places for the next photo, apologies!):

Note that mounts are an entirely different beast, so here’s each of them on the same bike, for comparisons:

I dive into the exact spec/feature/etc differences of these models later in the review (just before the conclusion).

The USB-C Port:

Yes, I’m doing it. I’m making an entire section that is fully dedicated to one photo, and one photo only: The USB-C port.

There, finally. Done. Took ya long enough, Garmin.

The Basics:

Note, if you’ve already used a cycling radar before, then I’d skip this section and just go to the next section. However, there is a new braking feature, which I’m including in this section, since it’s the singular new software feature that works across all existing bike computers (whereas the new fancy vehicle info bits, only work on newish Garmin bike computers). I’ve placed the braking bits at the end of this section.

With that, let’s take a quick look at the mounting situation first. Thankfully, the mount port itself hasn’t changed, which is great news for owners of existing Garmin Varia 3rd party mounts (of which there are tons on the market, including saddle mounts).

Instead, the mount attachment to your bike has changed and been beefed up. Gone is a single, simple band, and now a full strap:

You’ve got numerous seatpost mounts, per the unboxing section earlier.

What’s notable is that there’s now a setting to switch the orientation, so you can mount it upside-down if you want. Normal mounting puts the button on top, but there’s actually a setting to manually force it one way or the other. But by default, it’ll actually automatically detect orientation. Fun tidbit: If you leave it halfway (so totally wrong), it’ll actually warn you on the phone that it’s positioned incorrectly, and the message will instantly disappear when you move/fix it.

With that set, you’ll get it paired to your bike computer. On a Garmin Edge x40 or x50 series unit, it’ll offer to pair it via secure Bluetooth. Note that if you haven’t updated your firmware on your Garmin Edge unit since before February 2026, you’ll want to do that (otherwise the new features won’t show up). You’ll search for a radar sensor in the settings, and it’ll quickly pair up:

You’ll notice above that on a newer x40/x50 series device, when you pair it up, it’ll give you a quick overview of the user interface. For all other bike computers, it’ll just pair as normal.

This is because for these newer Edge computers, this will automatically pair the radar via secure Bluetooth, rather than ANT+ (more on this later on), however, it’ll still pair over the ANT+ lighting network for regular bicycle light features (technically speaking the radar broadcasts as two different device types: Radar and Bicycle Light).

Just for documentation purposes, here’s how the Garmin Varia RearVue 820 broadcasts:

– ANT+ Radar Profile (open standard)
– ANT+ Bicycle Light Profile (open standard)
– Bluetooth Smart Secured Connection for Cycling Radar (Garmin proprietary)

It does all of those concurrently, and according to Garmin, there’s no meaningful impact on the number of concurrent connections you have (which matches how these chipsets work). Note that if you’re pairing to any other bike computer (aside from x40/x50), you’ll see the Varia radar listed as a number instead, and you’ll just tap that instead, and it’ll save as a number instead of (in my case 286778, which is the ANT+ ID of my unit):

At the end of the day, your radar is paired (as both radar and bike lights) and you’re ready to ride. You’ll notice a little WiFi looking symbol in the upper right corner, indicating an active connection to the radar. If the radar runs out of battery, it’ll actually alert you the connection is lost, so you know there’s no longer radar coverage.

Once you start playing in traffic, you’ll see a stripe on the side of your bike computer. You can configure which side this is shown, as well as on the x40/x50 units, configure if you want this double-wide or single-column. Further, the Edge 1040, and 1050 also have a new half-screen option.

To begin, though, here’s the single-column option at right (most similar to the older option at left):

Here’s the double-column option (showing two lanes at right), notice the wider column (more on that in a minute)

And here’s the half-wide new data page option on the Edge 1040/1050/850 (no idea why the 550 is left out given it’s an identical screen as the 850), which lets you customize those data fields seen on the left side (or right side, if you configure it that way):

You can also do a full-screen view too, though this is really targeted more at bike commuters likely, than typical everyday riding for sport.

Now, before we go too far, I just want to be really clear on something: Cycling radars are historically all about tracking “overtaking” objects, so things that are closing in on you. Whether it be a semi-truck, a car, a cyclist, or even yes…a runner:

Or, horses (note that the full-size horse was seen as a red threat approaching, but the smaller pony behind it was not considered a threat):

However, Garmin’s newest feature is to also be able to track vehicles/objects that are the same speed as you. More on that in a moment.

Next, from a radar standpoint, you’ll see cars as they approach from behind on the screen. Each vehicle shows as a little oblong shape, with three different classifications for newer bike computers (bike/motorcycle, regular car, and large truck). For all other bike computers, you’ll simply see a dot per vehicle.

As the car overtakes you, it’ll be classified from a threat level, which includes *both* the overtake speed (relative to you), as well as the angular direction (which is new on the 820). Meaning, if it’s coming from a far lane to cross towards you at the last second, it’ll potentially escalate to red threat level. Otherwise, almost everything is orange:

Then the higher speed/threat ones show as red, such as this truck:

By default, when a car gets picked up on the radar, it’ll start to blink to get the drivers attention. You can turn this off, and likewise, you can enable so-called ‘peloton mode’, which turns off blinking altogether when riding in groups (to not annoy your buddies).

Once a car passes you, it’ll shift to a brief all-clear green:

As you can see from earlier screenshots, it can track multiple cars at once, including in separate lanes.

In a nutshell, the above is cycling radar – a concept that hasn’t really changed in a decade, and continues to be one of the few cycling tech products that there’s no real debate about being genuinely useful. The only people debating this (still) are the ones who haven’t used it. However, that’s not to say it’s valuable in all scenarios.

I don’t personally find cycling radars all that useful in the city, since there’s just so many cars around, it’s just non-stop action. Inversely, I find them super valuable descending mountain passes, where higher velocity speeds means it can be hard to hear overtaking vehicles. Likewise, I find it really useful out on long rides in the middle of nowhere, when you rarely see a car and may have slowly worked your way towards the center of the lane. It’s a nice mental reminder to be in a better spot before that vehicle blows by, especially if you’re hours into a long workout and mentally a bit tired.

Now, the next feature here (this one is new) is the ability to track vehicles (or cyclists) that are maintaining the same speed as you. Historically speaking, cycling radars have really struggled here. Without something closing in on you, radars just would drop the object. But here, Varia does a really really good job at holding the object. These cars, all traveling at relatively low speed with me, were kept on the screen:

And heck, even my wife cycling just behind me, would stay on the radar forever, largely correctly showing as a cyclist:

Now, the second piece is the light side of the equation. The radar unit is consider an ANT+ Bicycle Light, which virtually all bike computers support (and have for about a decade). This lets you control multiple lights in a group (e.g. front/back), as well as automatically turns the light on when you press start on a ride. Further, it lets you configure different bike light modes (flashing, intensity, etc…). You can access these in the settings:

These core modes haven’t really changed, though there is a new radar-only mode, which gets significantly higher battery life by turning off the light. However, there is a new option letting you create and configure your own light modes, with configurable blink patterns as well as intensity levels. You’ll create these via the smartphone Varia app:

That app also lets you monitor traffic in the same way as your bike computer would. This is handy for folks that don’t have dedicated bike computers, or may not use them on certain bikes (such as a commuter bike). Perhaps you’ve got your phone mounted on a commuter bike, and an extra mount on the back of that bike for your radar. Either way, you can see the same details on that too (at left, the Garmin Varia app on my iPhone, at right, the Garmin Edge 1050):

It’s also handy because you’ll get alerts via not just your phone, but any connected headphones (any connected Bluetooth audio device). So for example if you’ve got a pair of Oakley Vanguard’s, which have speakers in them, it’ll play the traffic alerts there too (again, in case you don’t have a dedicated bike computer).

This is notable, as Wahoo doesn’t have this feature in their ecosystem (though some other cheaper units do, such as that from Lezyne).

Finally, last but not least is the new braking feature. This uses an accelerometer inside the unit to determine braking action, and will illuminate the light brighter as you brake. We’ve seen this on other lights in various forms for years, and finally now seeing it on the Garmin radar units. In my testing of this (see the video), the changes in brightness level are honestly kinda hard to see. Yes, you see it, but it doesn’t slap you in the face, at least not in solid mode. It’s better in flashing mode, but not all countries permit flashing bike lights.

With all the basics covered, let’s get into the new advanced vehicle tracking a bit more deeply.

The New Features (Advanced Vehicle Tracking):

If you’re already familiar with how bike radars work, then this section is for you. You can skip all the basics, and get right into all the new ‘fancy’ features here, such as advanced vehicle tracking, multi-lane tracking, and more (whereas increased things like distance, battery, etc… are covered in the next section).

Now, the first thing to know is that everything in this section requires compatible firmware on your Edge unit, and is supported on the Edge x40 and x50 series devices (with the latest versions released/releasing this week). Note that other bike computers are still compatible with the radar for the existing radar functions, just not the new advanced vehicle tracking. Likewise, Garmin has confirmed that 3rd party display computers will not get access to the advanced vehicle metrics, saying:

“3^rd parties will not have access to the advanced vehicle tracking metrics, but will continue to have access to the same basic radar tracking as supported on RTL515.”

To be fair, the last umpteen times ver more than a decade that Garmin has offered unique/additional metrics to competitors, none of them bothered to take advantage of it, such as Wahoo never implementing cycling dynamics, or running dynamics.

In any case, the unit pairs up just like existing radars from Garmin, so that part is relatively straightforward (see the previous section of this review). From there, out on the road, here’s what you’ll see on a multi-lane road (took me a while to actually find one of those around here, almost everything is single-lane, or a highway).

The cars will roughly shift within the position of the radar line. So if a car is in a lane further from you, it’ll appear more towards the data fields, and if it’s closer to you, it’ll appear more to the edge. What’s notable here is this is super useful in places where you have bike lanes (or general lanes) requiring cars pass on both sides of you, such as this situation here due to a highway onramp for cars:

Or, any number of the bicycle lane death traps you’ll find across the US. Being able to see which side of you the car is coming up on is helpful, even if it’s not for every road (or even most of my roads).

In fact, it’s so sensitive I could even see my wife on the radar swerving around this sewer grate:

Next, you’ll notice there’s a bunch of color-coding going on here. Basically, cars are assigned a top-color based on their potential risk to you, from a direction of travel. So a car that’s not yet determined (size) is fuzzy white, then it shifts to crispy white, an orange car is a medium threat, and a red car is a high threat. But unlike radar of past where it was purely speed, this is taking into account trajectory. Also, all trucks/buses are always red threat level.

This whole-orange-topped thing is a mess. I couldn’t find a single piece of footage that didn’t show a car as orange (or red) by time it passed me. Notably, *ALL* large trucks/vehicles will be classified as red threat, no matter the speed. Ultimately, it makes every car a threat, no matter how slow it is, which means if everything is a threat, nothing is a threat. Likewise, we already had orange sidebars anyways, why do the tops of cars need it too?

In any case, as for sizing of trucks, in concept, knowing when a bit truck is about to pass you is super useful. Especially for smaller riders, where the draft/wind from the truck is significant. And in my testing, the vast majority of time trucks or buses trigger correctly as the larger truck/bus.

Another example here, this bus:

In terms of cyclists and cars though, cyclists do sometimes show up as cars, especially if not directly head-on (such as swerving a bit), like here. Further, the threat levels always often match reality, like my wife turning into a red-threat level cyclist while climbing.

And then if there’s rain, the entire vehicle classification bits fall apart entirely. More on that in a minute:

So looking at the new advanced vehicle metrics, I’m a bit mixed. There’s some elements that are pretty interesting in certain scenarios, such as knowing a big semi-truck is about to fly past you. Or, seeing cars properly tracked while keeping the same speed. Equally, the multi-lane piece, while taking more than just a ride or two, to get used to, can provide super valuable insights to those cyclists needing to ride in the literal middle of traffic.

Old Compatibility Mode (and Disabling The New Features):

Now, I just want to be really clear that existing bike computers can still work with the Varia RearVue 820 radar just fine. They simply don’t know the new features exist (because those new features are only shown with a secured Bluetooth channel). So doesn’t matter whether you have an Edge 530 device, an older Stages bike computer, an older Wahoo bike computer, or even a brand new Hammerhead Karoo 3 – all of them continue to function *EXACTLY* the same as before. Here’s the Karoo 3 with the Varia RearVue 820:

And here’s the Wahoo ROAM 3 with the Garmin Varia RearVue 820:

All is good there, and it works just like before. The thing you *won’t* get is the lateral vehicle placement, or the vehicle sizing. Also, you won’t get the color-topped cars (but you will still get red-threat level notifications like before). As an example of this within even the Garmin ecosystem, here’s the exact same moment connected to two bike computers. On the right is the Edge 1050 with the newer firmware, whereas on the left is an Garmin Edge using the regular ANT+ mode. You’ll notice how they display exactly the same number of vehicles, positions, and threat level (color coding). However there’s no lane placement on the older units, small/medium/large vehicle sizing, or orange-topped vehicles:

Now, what if you’re like me with a newer Edge x40 or x50 series device, and hate the new orange-topped vehicles? And perhaps want all vehicles to be circles again? Fear not, you can still get that variant back; it’s just a bit cumbersome. Basically, you need to pair with the Varia RearVue 820 in ANT+ mode, as opposed to the newer secure Bluetooth mode.

At first thought, you might believe that was as simple as choosing the pairing mode. But in reality, you can’t do that. Nor can you switch it after you pair up. So instead, you need to clog the pipes. No, not with Taco Bell, but with secure Bluetooth connections. In short, you need to temporarily clog up all three concurrent Bluetooth connections to the Varia Radar, and *then* go and pair your Edge x40 or x50 device, this way it shows the legacy ANT+ connection for radar instead.

That basically requires having a bunch of phones/iPad’s/whatever with the Garmin Varia app installed and paired via Bluetooth Smart, and actively on. You could do this with three phones, three iPad’s, two Phone’s and another newer Garmin device paired up in Secure Bluetooth mode, etc.. Doesn’t natter how you get there, you just gotta fill them up (temporarily).

So basically, here’s what you’re doing if you want to force legacy mode on a newer Edge x40/x50:

Step 1) Phone/iPad 1: Open the Garmin Varia app, pair it to the Varia 820 (remember to long-hold on Varia 820 to enable pink/purple pairing light)
Step 2) Phone/iPad 2: Open the Garmin Varia app, pair it to the Varia 820 (remember to long-hold on Varia 820 to re-enable pink/purple pairing light)
Step 3) Phone/iPad 3: Open the Garmin Varia app, pair it to the Varia 820 (remember to long-hold on Varia 820 to re-enable pink/purple pairing light)

Step 4) Now, with all that done (and active/open/showing connected), once again enable pairing mode on the Varia 820, and go into your Garmin Edge device and search for radars. You need to ensure it shows a number (your ANT+ ID), and *NOT* show “VariaVue820″, as the number means it’s ANT+, and the pretty name means it’s secure Bluetooth. It should look like this:

Step 5) Next, complete the pairing wizard. You’re done. That’s it. You’ll now see it listed as an ANT+ radar; you can rename it in the settings if you want to.

Step 6) Go forth and ride, free of orange-topped vehicles and misidentified vehicle sizes

Again, I’m hoping Garmin just simply adds a setting/toggle to the Edge x40/x50 series to disable the orange vehicle coloring and vehicle size pieces, especially given they don’t work well in the rain (and the orange piece provides no value anyway, as the screen is already illuminated orange).

Accuracy, Distance and Battery Testing:

First up is distance testing. Many radars make all sorts of crazy claims. It’s easy to make a claim, it’s hard to back it up in the realm world. Keeping in mind that there’s a difference between tricky range scenarios (e.g. in rain/fog, or of course around a corner), and then also optimal range scenarios (straightaways with nothing around).

Testing this is basically two pieces. First is the on-bike pieces as you’re riding. In this scenario, you’re looking to ensure that cars that come within this 170m (while overtaking speed) are triggered. It’s frankly as simple as that. In my case, I had a second Garmin device running the MyBikeRadar app, which shows the vehicle distance (according to radar), in order to validate some of these claims. When I’d see higher numbers, I’d see if that roughly matched reality. And it always seemed to.

Looking back at normal riding, on the bike yesterday, I rode with a Wahoo TRACKR radar, while my wife rode with the Garmin RTL-515 radar. Given its off/quiet season here, we could largely ride side-by-side, or her directly behind me the entire time. Thus while I was dual-recording the exact timings of the Garmin VariaVue 820 radar and Wahoo TRACKR radar, I could instantly hear her RTL-515 radar (since the bike computer was at most 1-2m behind my head). In *EVERY SINGLE* case, the Garmin VariaVue 820 picked up detection prior to Wahoo. In most cases (with usually slightly curving roads), this was often 3 seconds before Wahoo picked it up. Comparing to the olde Garmin RTL-515, that unit also beat the Wahoo, and was generally only 1-2 seconds behind the Varia 820, if any difference at all (most of the time it was identical).

Here you can see the Garmin already detected the vehicle, and it’d be upwards of 3 seconds further until Wahoo detected it:

Or here, simply out in real roads, where here the Wahoo stops tracking the cars behind my wife, because they are now same-speed with us. Whereas the Garmin shows both my wife as a cyclist, and then the first car behind her as a car (a few seconds later it’d pick up that second car too):

This performance from Wahoo matches nearly 10 months of testing on that unit. A unit that hasn’t seen a firmware update since last June, despite repeated claims by the company that they “have a new firmware coming any moment now to fix issues”. They’ve readily acknowledge numerous times, yet ultimately not fixed.

(Side note about testing, I usually flip the position of the radars throughout testing. But even when giving Wahoo the ‘better’ position higher up, it still performed worse than the Varia 820. Also note that these radars do not interfere with each other, and all radar companies test radars this exact same way).

In any case, the next piece of distance testing is best done in a controlled environment. In this case, I put the radars side-by-side simply to eliminate any vertical differences (though frankly at 170m+ away, a few centimeters won’t matter much), and placed them on the saddle the bike. Then, I marked out distance markers from my position, so I could tell when exactly a car was picked up. Finally, I stuck a drone in the air to pull it all together. I did this on a perfectly straight road, that’s virtually flat, on a clear day, in order to give it the ‘best possible’ scenario.

For example, this detection at 190m (though showed up a few seconds earlier on the Edge 1050), so realistically even a touch higher than that:

Now, just to explain the setup here a bit more:

1) The road is perfectly straight, and almost perfectly flat as well (for this stretch)
2) I placed my bike directly in the middle of the lane, at a warning post ahead of a roundabout (worked out great)
3) I then placed a drone in the sky, and went and measured every 50m, chalk-marking it as well
4) I used the MyBikeRadar app, which reports the vehicle detection distance transmitted by the radar itself (up to 196m)
5) Finally, I used Google Maps measuring tool to re-confirm the distances.

All in, the longest confirmable detect I had was 224.96m away. Here’s the detect occurring in the footage, note that the MyBikeRadar detect won’t show true distances above 196m, and itself takes about 2 seconds before it shows an estimated distance above 196m. Point is, that’s why it shows 0m, since it hasn’t been calculated there yet, but is showing up as a detect on the Edge 1050 shown below:

Note that due to the placement of the drone closer to the 200m marker, the perspective skews things very slightly for the 50/100m markers.

And then here’s it re-confirmed on Google Maps/Earth (note the position of the tree):

Over and over again on this straightaway road in perfect conditions, I was getting detects in the 190m+ range.

Now, there’s also a little quirk here, initially stumbled upon by GPLAMA. He noticed that when a vehicle was detected beyond the range of 196m, it could cause non-Edge x40/x50 bike computers to see it briefly (for a second or two) as closer than reality.

That’s because the ANT+ radar spec has a capped distance of 196m, and thus when Garmin transmits on that protocol (vs secured Bluetooth), if the vehicle is beyond 196m, then it’ll show it as a lower value first. So if a vehicle is at 210m, it’ll show as only 14m beyond you, then it hits 196m, and then it shows back at 196m again. You don’t see the actual value, but you *will* see the car jump from nearly running you over, to far far far away again. It doesn’t do this on the x40/x50 series devices with secured Bluetooth. Anyways, here’s a good example of this comparing a Wahoo ROAM showing the car directly behind me for a split second, before it shows the correct placement once it hits 196m:

(Above: All units connected to Garmin Varia 820 radar. Hammerhead Karoo 3 via ANT+, Wahoo ROAM 3 via ANT+, Garmin Edge 850 via ANT+, and Garmin Edge 1050 via Bluetooth.)

To be clear, this is a legit problem. And specifically, a problem for anyone with a non-Edge x40/x50 bike computer that has really straight roads. In my case, I never saw this problem in real life until I specifically went out and stayed on a super-straight road and tried to test it. That’s simply because my area doesn’t have a ton of roads like this. Whereas if I went to other areas (e.g. the Netherlands), this would be every day with super straight roads (well, assuming the constant rain didn’t reduce that top-end range a bit).

The good news is I think the fix here for Garmin is silly-simple: Just cap the ANT+ broadcast value to 196m. So if a vehicle is at 224m, just show 196m (putting it at the end of the distance bar). Once it gets below 196m, display value as normal. This would be super easy for Garmin to do on the Varia 820, and would instantly fix the issue (because changing the ANT+ spec is a non-starter at this point).

Update: As of Feb 10th, 2025, Garmin has confirmed a fix will arrive tomorrow for this via public beta.

Next comes accuracy, which revolves around false positives and false negatives. False-positives are when the radar detects something that’s not there. In most cycling radars, this tends to happen around metallic surfaces that the signal can bounce off of (such as in a city, or sometimes a metal garage door). Whereas false-negatives are when it simply doesn’t detect a car at all. That’s bad. Really bad. False negatives are virtually unheard of on the Garmin RTL-515. Whereas false negatives are much more common on the cheaper no-name radars.

Let me be super clear: There’s no reason to buy a radar if it has false negatives. It’s useless. Thankfully, that’s not the case here.

Whereas false positives, if rare enough, aren’t necessarily a deal breaker. By rare, I mean usually less than one per ride, or, if there’s a specific spot it happens on a given ride. Again, it’s not ideal, but it’s not a deal breaker.

In my testing with the Garmin Varia Vue 820, I’ve seen no false negatives. And likewise, out riding I’ve surprisingly seen no false positives either. Even on rides where the Wahoo TRACKR had false positives, the Varia Vue 820 didn’t. Which isn’t to say that I won’t eventually get one, I just haven’t had one yet riding. Whereas I have seen two false positives standing off to the side of an quiet intersection, when an approaching vehicle from a side the radar couldn’t see reflected off all assortment of cars/etc to momentarily flag before disappearing. But that’s it.

Now, the singular area where I see ‘accuracy’ issues is the *type/size* of vehicle it detects, when it rains out (or, when the radar gets wet from a puddle). To be super clear, this is not impacting whether or not the vehicle is detected, but rather, whether it detects it correctly. I find that the split-second water gets on the radar, the accuracy of the vehicle size goes out the window. Cars become cyclists, my wife riding her bike becomes a bus/truck, and cyclists become cars. It’s a mess.

Likewise, the way Garmin uses theoretical vehicle size as a element for threat level means that my wife on the bike can quickly escalate to a red-level threat if it mis-detects her as a vehicle, such as this moment:

Or here as a cyclist, but with orange level threat:

And that’s in addition to the number of times a vehicle is detected as a cyclist if it’s behind a cyclist, such as this, which shows two cyclists and then a car. There are actually two cars back there (which it seems correctly a few seconds later). Mind you, Wahoo only ever saw one car here.

But if we set aside the vehicle classification pieces, the range/detection/etc bits area still really good. Just not the actual vehicle size, which in turn means it can (and often does) misclassify threat levels. I’d strongly encourage Garmin to add an option to simply turn off vehicle sizing, as it becomes a distraction with the vehicles constantly changing size and unnecessarily escalating threat levels.

When it comes to battery, I tested the two core modes I’d use: Solid-on and peloton mode (solid on, but reduced brightness for group riding, with no flash when a vehicle overtakes). Here in Europe, constant flash is frowned upon, so that’s not something I tested, though, that gets higher battery life than the modes I was testing.

Solid-On (Low Setting): I used this during daylight hours, and the claim is 10 hours of battery life. In testing at 1hr intervals, the battery did indeed deplete at approx. 10%/hour. For example, starting one ride at 82%, I then checked it 1hr 20mins later, and it showed 68%. This repeated for all of my other rides in this mode (which are most of them), near-identical.

Peloton Mode (Solid-on): In this mode, Garmin’s claim is 15 hours of battery life. In a ride yesterday for 2hrs 20mins, I checked at the 2hr marker, and the battery had gone from 65%to 50%, so an estimate of 13.33hrs. The only slight caveat is the first 10-15 minutes of that I was in solid-on mode (which burns 50% more/hour), before my wife reminded me to switch. Thus the very slight undercutting of the 15 hours claim.

Radar-Only Mode (Light off): In this mode, the light was only activated as a flashing light when a vehicle approached, otherwise it was off (you can turn that off too).In this scenario, I took measurements on the hour, and after the first hour it went from 98% to 94%, thus a 4% decrease, or 25 hours battery life. Thus falls short of the  battery claim of 30 hours in Light Off mode, but perhaps that mode also includes turning vehicle detection flash off entirely (which, currently a bug is preventing me from doing, once the Edge connects to it).

One thing to keep in mind with claims around battery life is that, like watches, it’s really hard to just put these in a dark room overnight and estimate battery life. First, there’s no vehicle activity to work the radar tracking components. And second, a static/still environment won’t work/trigger the accelerometer and gyroscope used to detect braking action. So while this is good for light testing, it’s not super practical for other applications.

Nonetheless, for fun, I set it on low mode, put it in the bathroom overnight, and let it roll:

Starting point, at 2:20M was 98%, and by 8:20AM it was 43%, so it burned a bit less than the usual 10%/hour, but not massively so, closer to 9%/hour.

Thus, from an overall specs/claims standpoint, it’s meeting or exceeding nearly all of its claims, and easily beating most competitor claims.

User Replaceable Battery:

I just wanted to very quickly note that the unit does have a user replaceable battery. This is required per EU regulations, and we saw the Garmin Edge 550 & 850 implement it this past fall. Now the Garmin Varia RearVue 820 has joined that club.

It’s designed for when your battery dies many years down the road, not for just swapping batteries on a long trip. Garmin will be required to make replacement batteries available at pretty much their, thus the replacement prices should be reasonable.

Changing the battery requires a T5 Torx bit, and then there are six screws on the outer case, followed by three more screws inside. There’s a single ribbon cable attaching the battery that just easily pops off. The entire disassembly took me about 90 seconds.

Radar Model Comparison:

Perhaps I’ll expand out this section into its own dedicated post at some point, but in terms of features and a product tech spec comparison, here’s all the official claims in a single comparison chart (remember comparison shots up earlier in the post):

Of course, on paper, some of these seem similar. But in reality, the big ticket item here is accuracy and detection of the radar. It’s clear Garmin is using a new underlying radar chipset here, and certainly, their existing one is widely considered the gold standard. In my continued testing, the existing model easily beats Wahoo’s TRACKR radar in terms of accuracy/reliability (side-by-side), while the newer Lezyne radar is really good in my testing thus far, though not quite as good as either Garmin unit (but better than Wahoo).

Final Thoughts and Recommendations:

The Garmin Varia RearVue 820 is clearly the best radar on the market. There’s simply no comparison there in terms of real-world detection range, accuracy, same-speed vehicle detection, and solid performance around things like false-negatives and false-positives. It’s clearly the new gold standard in underlying radar hardware. But with it are a host of new software features too, some of which are super useful in certain messy-lane scenarios, like lane detection. And equally, knowing when a giant truck is about to pass you.

At the same time, some of these new software features can be a bit overwhelming, especially in the first few days of riding. Thankfully, most of them are optional and can be easily turned off. But there are still some that are less reliable, such as vehicle type classification in the rain, that clearly need more work. The same goes for how it color-codes every single vehicle as orange, defeating the purpose of color classification. I’d like to see Garmin offer two toggles in the radar settings, one to disable vehicle classification, and one to disable some of the excessive color-coding. They already have similar toggles for other features in the radar, so these aren’t too much of a stretch.

Beyond that, there’s the 196m bug for other ANT+ bike computers, which I mentioned earlier. Literally minutes before publishing, Garmin confirmed via e-mail that this bug will be resolved tomorrow in a public beta update. It’s a silly easy fix for a mostly minor issue, but equally, this never should have slipped out of testing. In Garmin’s push to reduce leaks over the last year, it’s dramatically shrunk its external beta testing pool, and as a result, we’ve seen a very clear rise in launch-day bugs/issues across the majority of Garmin’s marquee products. Bugs that should have been caught, and equally, we’ve seen a rise in reviews highlighting these issues. It seems like Garmin needs to find a better way to navigate that situation.

Setting that aside, though, in terms of this radar, it’s ultimately the best product on the market today – and from a pricing standpoint, Garmin knows it. They know if you buy a random $100 knock-off radar, it’s going to miss cars and be pointless (as countless reviewers have shown), and they know if you want the previous gold-standard radar (the RTL-515), you can still buy that micro-USB-laden unit for $149. Ultimately, I’d love to see a USB-C version without all the new lane detection/etc bits for $199 (but including the increased range). Whether or not that happens, I guess I can dream.

With that, thanks for reading!