Review: Serfas Thunderbolt Red Tail Light

A bright and lightweight light

Lights Lights Shootout

2015 Lights Shootout

Serfas Thunderbolt Red Tail Light Front

The Serfas Thunderbolt doesn’t sound noteworthy until you get your hands on it. It’s about the size of an AA battery, but when you turn it on, it’s like a light fountain. The Thunderbolt headlight puts out about 90 Lumens and the tail light about 30. It is just so incredibly bright for its size and weight.

It’s got a simple form factor too and can it can be placed in a lot of areas on the bike. It has four ears on the corners and it’s attached to any tube with two big rubber straps. This tail light is best in flash mode, as it is very visible day or night.

It’s aged a little bit in the last two years since it was introduced and $40 is a little pricey now compared to the competition. Also, mounting is not that versatile if you don’t have a pipe or surface to strap on to. The angle of the tail light is not ideal when mounted on the seatpost, but the light is so bright it hardly matters.

Video: Test with the Serfas Thunderbolt Red Tail Light. Tail Light was shot from 20 yards away with a camera at fixed exposure. The light was pointed at the camera then turned to the side. Different flash modes were activated.

The new clear housing really improves side visibility on this light.

Integrating Sphere Measured Lumens

This light measured 31 Lumens in an integrating sphere. Claimed Lumens by the manufacturer is 35 Lumens. The Lumen-hour graph below shows how the light performs over the first three minutes of its battery cycle. Compare all Lumen Tests here »

Serfas Thunderbolt Tail Light Lumen Chart

  • Great output with omnidirectional ‘to be seen’ light
  • Awesome size and weight
  • Good side visibility with clear housing
  • Has matching head light available
  • Price is a bit high now at $40
  • Run time is limited at 1:30
  • Should have more mounting options on the backpack or clothing
  • Price: $40
  • Claimed Lumens: 35 Lumens
  • Measured Lumens: 31 Lumens
  • Time on High: 1:30 Hours
  • Charge Time: n/a Hours
  • Mounted Weight: 40 grams
  • Category: Tail Light
Overall Rating

4.5 Stars 4.5 out of 5 Stars

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This article is part of Mtbr and RoadBikeReview’s 2015 Lights Shootout. To see all the bike lights tested CLICK HERE.

About the author: Francis Cebedo

The founder of mtbr and roadbikereview, Francis Cebedo believes that every cyclist has a lot to teach and a lot to learn. "Our websites are communal hubs for sharing cycling experiences, trading adventure stories, and passing along product information and opinions." Francis' favorite bike is the last bike he rode, whether it's a lugged commuter, ultralight carbon road steed, singlespeed or trail bike. Indeed, Francis loves cycling in all its forms and is happiest when infecting others with that same passion. This obsessive personality has also turned him into a bit of an addict when it comes to high quality coffee and IPAs.

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