Garmin Varia RTL510 Rear Radar System Review


“Life saver.”

“Over engineered mirror.”

“Best product I’ve bought for my bike.”



“No one should ride without one.”

I’ve heard all of the above said about the Garmin Varia radar system.  A bit like ebikes, the Garmin Varia RTL510 is a polarizing product – especially for those who have not tried it.  For every person who loves their Varia, there seems to be another saying it is a gimmick.   In hopes of shedding some reality, here is our take on this second generation radar system.

What is the Garmin Varia Radar System?

The concept and intent of the Garmin Varia radar system is simple.  Outside of being a very good “smart” safety light, the Varia’s distinguishing characteristic is that it shows you as a vehicle is approaching behind you.  Yes, part of what the Varia does is what a mirror tries to do – let you know when a vehicle is behind you.  However, comparing the Varia to a mirror is like comparing a F-35 to the Wright Flyer.  While both a mirror and the Varia are designed to help you see what is behind you, the Varia is nothing like a mirror in terms of its execution, convenience, performance and even its safety.

Garmin Varia Radar Display

For those that aren’t familiar with the Varia, it pairs with a compatible device (a list of the most common is included later in the post) and displays up to four vehicles approaching from behind on the left or right side of the screen.  It takes up a small amount of screen space on the left or right side of your Garmin display (you can assign it left if you don’t like the default right) and you can still see the majority of your display.

The video below can help you understand the fundamentals of how the system works and integrates with a cycling computer better than words.

Colors Indicate Speed

When the Varia detects a vehicle, the side of the screen flashes and, if wanted, an audible tone.  The approaching vehicle then shows up as a “dot” on the Varia.  The general speed category of the vehicle is assigned by the color of the dot.  An amber light signifies a moderate speed vehicle approaching, red signifies a higher speed vehicle approaching and green means that all vehicles have passed and it is clear behind you.  You can also see the dot proceeding up the side of the screen and get an idea of distance and speed that way as well.

 Where Does the Garmin Varia Work and Not Work?

The Garmin Varia works best on open rides that are not in urban “stop and go” environments.  In fact, the Varia would likely be a bit of a disaster in a city as there is just too much traffic around for it to process or provide helpful information.  The number of false readings will be high in a city.  Besides, in urban riding, you should assume that there is a vehicle approaching behind you.

The Varia is ideal on more open roads – paved or gravel.  If you ride on roads where there is low to moderate traffic patterns, the Varia thrives on these types of rides.  On my mostly rural rides, the Varia has few false readings and it proves a very reliable and helpful companion.  In fact, the Varia frequently alerts me to cars before I hear them.

Range and False Readings

The Varia will detect vehicles approaching from behind starting from 460 feet back. While you should always physically look behind you before pulling into a lane, I’ve never had the Varia not see a vehicle approaching from behind.  The Varia does not ever show vehicles approaching from the front.

I have seen a very small number of false readings on my mostly rural rides.   A dot will show on the screen, but no car passes.  This tends to happen when there is cross traffic behind me.  For example, climbing up from an interstate underpass can sometimes detect the cross traffic on the interstate.

Will Riders Behind Me Show on the Varia?

Outside of pelotons and larger groups, the Varia does not show other riders behind you.  Likewise, if you are leading a small group/paceline, you won’t see those riding behind you on the Varia.

Garmin Varia RTL510 Compatibility

Garmin RTL510 and Edge

As of late 2019, the Garmin Varia RTL510 is compatible with all recent Garmin computer heads.  This includes the Edge 1000, Edge 1030, 510, 520, 530, 810, 820, 830 as well as many Fenix, D2 and other Garmin head units.

Garmin has made compatibility of the Varia “open source” – they want it to work with as many head units as possible, regardless of manufacturer.  Many display units have the potential to work with a product like the Varia, but many are not currently set-up to display the Varia.  This being said, Wahoo recently enabled the feature in many of their computer heads, so there are other brands of display that you can use the TRL510 with beyond Garmin.

Garmin Varia RTL510 Safety Tail Light

I think that the industry’s pursuit of the absolute brightest safety light possible is a little misguided.  The approach is similar to what it would be like if the auto industry just made headlights brighter and brighter and not taking into account what that does to on-coming drivers.  Brighter is not always better.

Beyond the radar, the Garmin Varia is a good “smart” safety tail light.  While a number of “safety” lights are obnoxiously bright to the point of dangerous, the intensity of the Garmin Varia RTL510 does a nice job of providing a very visible light without going too far like some.

The RTL510 displays a safety light in a 220 degree range with daylight visibility of close to a mile.  This means that the light is visible from a great distance and from most directions.  Pair it with the complementary Garmin UT800 front light (we’ll post a review soon) and most riders will have all their bases covered.

Small and Light

With its narrow profile The Varia RTL510 fits nicely behind most seatposts and has a notably more attractive and finished look than its predecessor.  It no longer looks like a prototype from a lab, it looks like a finished product.   The Varia is minimalist gear, taking up only a little more room than the flashing light I would otherwise use, but providing significant features for that small weight and size increase.  I like to ride minimalist, so I like this approach!

Garmin RTL510 Battery Life

The Garmin RTL510 claims up to 15 hours of power in daytime flashing mode and up to 6 hours in the solid or pulsing night mode.  I have not been on a singular ride long enough to test this contiguously.  I do know that the battery lasts 3-4 back and forth daylight commutes of 3+ hours between charges.

Garmin Varia RTL510 Price

Not including a compatible head unit, which many riders already have, the Garmin Varia RTL510 is $200.  While some will see this as a really expensive rechargeable safety light, in our experience, the reality is more that it is a really well priced radar system.  There are few things, regardless of price, that can make a rider feel safer on their bike.  $200 seems very reasonable for this level of confidence.

Great Gift?

Cyclists are notoriously hard to buy gifts for.  Beyond fit related variables, many riders are particular as to what product or service they use.  It is easy for a well intentioned cycling related gift to backfire.  This is why we often recommend gift cards or certificates instead of a specific item as a gift.

This being said, the Garmin Varia RTL510 could very well be an exception.  It is perfect in that many cyclists are likely to not have purchased one for themselves, yet would greatly appreciate such a product once they used it.  As an added bonus, you can rest assured that you are likely enhancing the safety of that rider simultaneously.  The Varia has all the makings of a great gift.

Contact us to purchase.  While we know it is easy to click a “buy now” button somewhere, buying from us helps us keep writing product reviews and providing the fit and mechanical services that we offer. We’re happy to ship.

Garmin Varia RTL510 Radar System Conclusions:

I mentioned the polarized nature of the Garmin Varia RTL510 being similar to ebikes; on first mention the Varia is either lauded as the second coming or vilified as another example of technological excess.   So, which is it?

The Varia system is not new; this is a second generation product and we have sold dozens.  And I can’t recall anyone who has tried the system that didn’t like it once they used it.  In fact, I can’t think of any product in recent years that I’ve had more people seek me out after getting one to let me know how much they appreciate the system.  In the end, that makes for a simple litmus test.  While not perfect, the Garmin Varia is an exceptional product that is simple, reasonably priced and very effective at helping riders feel safer.

It falls under the heading of products that once you try it, you won’t want to ride without it.  From our perspective, it is hard to put a price on that.

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