Advantages and Disadvantages of Rearview Radar for Road Bikes

What is a road bike rearview radar?

A road bike rearview radar is a “proximity sensing sensor” that is mounted on the rear of the bicycle.

Its main role is to detect the approach of a vehicle passing from behind and notify the rider. This is expected to enhance safety when riding and contribute to the prevention of traffic accidents.

In automobiles, functions to recognize approaching vehicles, such as rear cameras and corner sensors, are increasingly being installed as standard equipment. In bicycles, however, this accessory is still not widely used, but it has gradually gained recognition in recent years.

Advantages of Using Rearview radar for Road Bikes

The advantage of a rearview radar is that it can properly detect hazards.

Unlike cars and motorcycles, road bikes are not often fitted with side mirrors, and rearward checking is done by looking backward. This in turn tends to make people inattentive to the road ahead, so it is normal for road bikers to check behind when changing lanes or turning.

This leaves them vulnerable to vehicles approaching when they are not looking backward, but by installing a rearview radar. Rear view radar allows them to constantly check their rearward position and the rider can see approaching vehicles on the cycle computer.

Rearview radar also work effectively at night and in bad weather, so they have the added benefit of enabling safe rearward checking even in poor visibility conditions.

Disadvantages of Rearview radar for Road Bikes

Although rearview radar make road bike riding safer, the biggest disadvantage is that they are not completely reliable.

If a vehicle approaching from behind is fast or if there are many vehicles around, there may be a delay in the sensor’s response. Therefore, the use of rear sensors does not eliminate the need to check the rear of the vehicle, but only to provide support.

In addition, a rearview radar is meaningless on its own and must be used in combination with a cycle computer or smartphone. The rearview radar alone costs more than $100, and if you also need a compatible cycle computer, you will be investing several hundreds dollers.

It is up to the individual to decide if he or she should invest in an “expensive bicycle accessory that does not work perfectly.

What to look for when choosing a rearview radar for road bikes

Detection range and accuracy are important

The performance of a rearview radar is determined by its “detection range” and “detection accuracy.

Naturally, the wider the detection range and the higher the accuracy, the higher the performance of the rearview radar.

On the other hand, if the detection range is narrow or the accuracy is low, “the car was already approaching when the sensor detected it”, and accidents and dangerous situations cannot be avoided. This makes it meaningless to install rear sensors.

The detection range of rear radar is determined by the “sensing distance” and the “radar’s vertical and horizontal range angles. The longer the sensing distance, the better, and the wider the range angle, the better the accuracy of detection on curves and other non-straight lines.

Let’s also check compatible devices and warning methods.

Since the rearview radar is basically attached to the seat post, it does not warn on its own, but rather on a display linked to a cycle computer or other device. Depending on the linked device, there are different warning methods, such as vibration, flashing lights, and audio alerts, but they are meaningless if the warning is not understood.

Cycle computers may display the detection signal on the vertical side of the screen, or a cycle computer with LEDs may use LEDs to notify you, but you should decide which is easier for you to see according to your style.

Also, make sure that your cycle computer or smartphone can be paired with a rearview radar. Basically, you will connect with either ANT+ or Bluttooth, but some products can only be connected with either, or the cycle computer may not support rearview radar.

Battery life is also important.

Since rear sensors are battery-operated, “how long they last” is also very important. Especially on long rides, it will be stressful if the battery runs out in the middle of the ride, so choose a model with as long a battery life as possible.

If you are going to use it for long rides, you should choose a rear sensor that can be used for more than 10 hours.

Main Rearview Radar Sensors for Road Bikes

Garmin Varia Rearview Radar

The gold standard in rearview radar sensors for road bikes is Garmin’s Varia series. The latest models include the RTL515 (3rd generation) and the budget-friendly RVR315. The previous generation RTL510 has been discontinued by the manufacturer and is now only available as leftover stock.

Garmin Varia stands out for its unmatched accuracy and reliability, thanks to Garmin’s long history in producing both commercial and consumer-grade sensors. Another major advantage is its compatibility with bike computers—not only Garmin’s Edge series but also many third-party devices that support rearview radar.

The key differences between the RTL515 and RVR315 lie in the presence of a taillight and battery life. The RTL515 includes an integrated taillight and offers longer runtime, making it a better choice for long-distance rides. The RVR315, while more affordable, offers only 7 hours of use, which might be insufficient for all-day rides.

Bryton GARDIA R300L

Bryton, Garmin’s cost-performance rival in the bike computer space, released the GARDIA R300L rear sensor in 2023.

Priced about ¥8,000 lower than the Garmin RTL510, this model comes in under ¥20,000 while offering superior specs: a detection range of up to 190m and battery life of up to 17 hours. Although it’s a newer entry in the market, Bryton’s solid reputation in cycling electronics adds a level of reassurance.

Magene Radar Rear Light L508

Produced by Chinese manufacturer Magene—known for affordable power meters, bike computers, and smart trainers—the L508 offers a strong value proposition. Japanese distributor Growtac, known for brakes and rollers, handles domestic sales.

As is common with Chinese brands, Magene offers aggressive pricing. This rearview radar provides solid performance for under ¥20,000, and sometimes even cheaper through international retailers. It’s a top pick for riders looking to try radar tech on a budget.

iGPSPORT SRTL SR30 Smart Radar Taillight

Chinese cycling electronics brand IGPSPORT offers this competitively priced radar taillight. With similar specs to its competitors but a lower price point of ¥16,830, it’s a strong contender in the market.

Note that it is currently only compatible with iGPSPORT’s own computers, specifically the iGS630 and BSC300 models.

TREK CarBack Radar Rear Bike Light

This is TREK’s official rearview radar. While designed by TREK, it transmits data via both ANT+ and Bluetooth, allowing use with non-TREK devices just like other third-party sensors.

What sets it apart is its impressive 240m detection range—about 100m longer than most other models. It also integrates a taillight and is competitively priced at around ¥25,000. The only downside is its relatively short battery life of up to 7 hours.