There are many reasons for wanting to be able to ride a mountain bike on singletrack at night. The reasons range from wanting to do longer rides after work than daylight allows, wanting to participate in a race format that requires riding at night such as a multiday race or 24 hour race, or simply being able to get home when an afternoon ride runs long due to an untimely mechanical, a slow trail, or an overambitious ride plan.
Everyone has been in a situation when the sun goes down, visibility approaches zero, and a ripping piece of singletrack turns into a long hiking trail because riding by starlight is impossible.
Then there’s the simple reason that riding bikes in the dark is novel and fun. Whatever the reason, there are a certain things that can make riding in the dark an enjoyable experience rather than one to be dreaded.
Amount of Light
When riding at night, the speed you will be comfortable maintaining is directly correlated to the amount of light available. While it is possible to putter down a trail with only a small headlamp, a bright light will allow you to ride at nearly full speed.
Light output is measured in lumens and the brightest bike specific lights on the market currently are rated at a staggering 3,000 lumens. In comparison, a standard commuter light output is about 150 lumens.
Of course, more lumens equates to a larger light and heavier batteries. While 3,000 lumens may be great for a racing scenario — where the added speed possible due to the increased visibility would make the extra weight worthwhile — no one wants to carry around an extra pound of lights on all rides as a backup in case the sun goes down before the ride is over.
The happy medium with light seems to fall around the 1,000 lumen range. A 1,000 lumen light will weigh in around half a pound (about the same as a point and shoot camera) and will produce ample light for riding singletrack at a reasonable pace.
For racing on trails at night, most people tend to be happy with about 1,500 to 2,000 lumens, generally split between a handlebar light and a helmet mounted light. These setups will generally weigh in around a pound, including batteries.