Bike lights

How to choose your bike lights

The first question isn't how many lumens, but what you need the light for: be seen or see the road. The two purposes call for different brightness levels, beams and budgets. And road rules require a white front light and a red rear light from dusk onwards.

Be seen: 20 to 100 lumens

In town and on lit roads, lights make you visible. Around 100 lumens at the front and 20 to 80 at the rear are more than enough. What matters here is side visibility, the flashing modes that catch the eye, and battery life. Compact models (Knog Plus, Lezyne KTV) fit in a pocket and mount without tools.

See the road: 400 to 2,400 lumens

• 400 to 800 lumens : unlit country roads at a moderate pace. The minimum you need to spot a pothole in time.
• 800 to 1,500 lumens : the sweet spot for riding fast on roads at night and on easy-going trails.
• 1,500 lumens and above : night-time mountain biking and technical descents, where you need to light up a wide area and see far ahead at the same time.
• Above 1,000 lumens, most lights can sustain maximum brightness for only 1½ to 2 hours. Check the battery life at the brightness setting you'll actually use, not at the eco setting.

The beam matters as much as the lumens

A well-designed road light has a beam cut off at the top, which lights the road without dazzling oncoming drivers. A mountain bike light casts a wide beam to cover the singletrack. Even with the same lumen output, these lights perform very differently — and using a mountain bike light on the road can endanger oncoming traffic.

Features that make a difference

• The brake light (Sigma Buster RL, BBB Signal Brake) shines brighter when you slow down, as detected by an accelerometer. A real safety benefit when riding in a group.
• The rear radar (Garmin Varia, Wahoo Trackr, Coospo TR70) detects approaching vehicles and alerts you on your GPS bike computer. It's one of the most significant road-safety accessories of recent years.
• The adaptive modes (Lezyne Ai Alert) adjust brightness to ambient light and speed.
• The dedicated Garmin, Wahoo or GoPro mounts let you mount the light beneath the bike computer mount rather than on the handlebars — neater and more aero.

Mounting and charging

Check the handlebar or seatpost diameter you're mounting it on, and the mounting method: a slip-on silicone strap (quick, universal), a screw clamp (more secure at high speed), or a quarter-turn interface. On a seatpost aero, you need a dedicated mount — the detail most often overlooked. As for charging, theUSB-C has become standard; a few models still have a removable battery, useful on very long rides.

Front and rear lights, or a kit

Kits (Knog Twinpack and equivalents) cost less than buying two lights separately and are enough for urban riding. Once you're riding properly at night, it's better to choose them separately: a powerful front light and a highly visible rear light have different price points.

To find out more: How to choose your bike lights

See also: Bike light parts and accessories · GPS bike computers · GPS and camera mounts