Summary of advantages and disadvantages of rearward sensors for road bikes and main products

Posted at: Apr 12, 2023

Rearward sensors for road bikes are important accessories that increase safety when cycling. The following is a summary of their advantages and disadvantages and a comparison of specifications of major products.

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What is a road bike rearward sensor?

A road bike rearward sensor 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 Rearward Sensors for Road Bikes

The advantage of a rearward sensor 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 left.

This leaves them vulnerable to vehicles approaching when they are not looking backward, but by installing a rearward sensor, they can always check their rearward position because they can see approaching vehicles on the cycle computer in their hand.

Rearward sensors 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 Rearward Sensors for Road Bikes

Although rearward sensors 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 rearward sensor is meaningless on its own and must be used in combination with a cycle computer or smartphone. The rearward sensor alone costs more than $100, and if you also need a compatible cycle computer, you will be investing several tens of thousands of yen.

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 rearward sensor for road bikes

Detection range and accuracy are important

The performance of a rearward sensor 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 rearward sensor.

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 rearward sensor 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 rearward sensor. 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 rearward sensors.

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 rearward sensors for road bikes

Product Sensing Distance Range Angle Battery Time
Garmin Varia Rear View Radar RTL510 140m Non-public up to 15 hours
Bryton GARDIA R300L 190m Non-public up to 17 hours
Magene Radar Rear Light L508 140m up to 40° up to 16 hours

Garmin Varia Rear View Radar

Garmin’s Varia is the standard for rearward sensors for road bikes, and now the second generation RTL510 is available.

The main appeal of Garmin Varia is the high accuracy and peace of mind that comes from Garmin, which has been manufacturing sensors for commercial and private use for many years, and its affinity with cycle computers.

The Edge series of Garmin cycle computers as well as most cycle computers that support rearward sensors are compatible with Garmin Varia, so there is the advantage of not having to choose a cycle computer.

Bryton GARDIA R300L

The GARDIA R300L is a rearward sensor released in 2023 by Bryton, which also competes cosmetically with the king of cycle computers, Garmin.

The biggest advantage of this product is that it is $80 cheaper than its rival, Garmin’s Varia RTL510, and can be purchased for less than $200. It is also higher than Garmin’s Varia RTL510 in terms of performance, with a maximum sensing distance of 190 meters and a battery life of up to 17 hours.

Although this is a new product to the market, it is a rearward sensor from Bryton, which has a certain reputation for cycle computers, so there is a sense of security.

Magene Radar Rear Light L508

This rearward sensor is from Magene, a Chinese manufacturer of inexpensive power meters, cycle computers, and smart trainers.

The affordable price is typical of Chinese manufacturers, and a high-performance rearward sensor can be obtained for less than $200. Some products are sold for as low as $140 at overseas retailers, making them a good first choice if you are looking for a low-priced product anyway.

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