See.Sense Ace rear light review

See.Sense has packed a ton of safety and even road and traffic response and report tech features into its lightweight Ace rear light. So is it the benchmark beacon of the future?

See.Sense Ace rear light overlaid with a recommends badge
(Image: © Guy Kesteven)

Cyclingnews Verdict

See.Sense ACE is a great fit and forget, multi-smart function safety booster for you and even your regular riding areas without being bulky or excessively expensive. Side visibility is limited though and it can be dazzling on pack rides.


  • +

    Sentient rear light safety

  • +

    Light, bright and waterproof

  • +

    Range of effective bike and body mounts

  • +

    Easy smartphone control

  • +

    Theft and crash alerts

  • +

    Fast recharge

  • +

    Traffic/road feedback for planners

  • +

    Basic fun ride facts


  • -

    Limited side visibility

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    Not as punchy as single LED lights

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    Traffic modes can currently irritate following riders

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See.Sense is all about expanding what bike lights can do for you and your riding environment, and the Ace stands out as a smart enabled, sentient safety booster with ride reporting and smartphone app control tech. It’s still an eye-catching, compact, waterproof and easy to use rear light from a practical point of view too and really well priced considering the level of tech it comes with. 

With that said, the wide-angle visibility isn’t so great, and automatic traffic safety measures can be anti-social on group rides, but with those two concerns in mind, how does the See.Sense Ace fare in a test against the best bike lights on the market?

The See.Sense Ace rear light on a bench next to its mounting bracket

The See.Sense Ace features a flat face and a large number of small LEDs, rather than a single high-power bulb (Image credit: Guy Kesteven)

Design, specification and performance

Despite its huge feature list, the See.Sense Ace is physically quite small, with a wide flat clear lens over a sheet of COB LED bulbs and the broad silicone power button sitting in the top third of the ‘screen’. The mount is a new design to us too, with a separate cradle that you plug either a round or aero-tube-shaped rubber shoe into and then strap in place using one of the five different sized O-rings provided. The light then clips into this holder using two central slots or upper or lower slots that are slightly angled to level out the light on sloped surfaces. If I'm honest this seemed worryingly flimsy at first but while it certainly wobbles about a lot, I’ve been battering the Ace all over the place on road and gravel and it's still with me. It’s never faltered even when filthy or subjected to several hours of continuous rain and rear wheel spray so the IP67 waterproof rating rings true. The ACE is packaged with a bag and pocket clip too, or a GoPro style mount can be added for £9.99 / €11,65.

The See.Sense Ace rear light laid sideways on a bench next to its mounting bracket

Three angled slits on either side allow the light to be tilted, while five different sized O-rings and two seatpost brackets are included to help you achieve the perfect fit (Image credit: Guy Kesteven)

Despite a claimed 125-Lumen maximum output, it’s not as explosively visible at very long range as single high power LEDs we've compared it against, as the power is spread across multiple tiny LEDs. The flat design means sideways visibility is limited to incidental spill rather than any specifically directed power too. It’s still very visible from the rear 3/4 though with a constant mode and five different flash/strobe/pulse settings you can toggle through manually via the big silicone button or select via the Smart.Sense smartphone app. The app also lets you switch on the ‘brake light’ function that increases brightness when the onboard accelerometers sense you’re slowing down suddenly.

The accelerometers combine with light sensors and onboard processors to increase brightness and/or flashing rate of the Ace in response to sudden swerving or direction changes that it perceives as busy or dangerous traffic situations. It also responds to increases in surrounding light levels by increasing power and flash rates. Unlike the See.Sense Beam front light, those functions can’t currently be turned off, so the Ace can get excitable on twisty roads or when triggered by the lights of following riders which won’t make you popular in the pack. See.Sense tells us that might be changed in the firmware shortly though.

Piggybacking the GPS in your phone via the app (or linking it to one of the best cycling computers) lets it record basic speed and distance ride data and even gives you approximated calorie counts (in kcal or banana/coffee/donut/pizza equivalents, commuting fuel savings and CO2 offset). It’ll even collect all the stop, start, rattle and swerve data you collect on your rides, add any notes you want to include in your ride report, and parcels them up as anonymised data which you can forward to See.Sense or your local authorities to provide up-to-the-minute traffic data to help with their planning. 

The accelerometers also provide theft- or crash-alert functions, which will tell you if your bike is moving when you're not on it, or notify a designated saviour that you aren’t moving anymore. They obviously depend on Bluetooth range/phone coverage but they’re definitely useful features that make the See.Sense Ace a real safety booster. 

Despite all the sensing and thinking it's doing, the ACE still runs for ten hours in flash mode off a two-hour charge via the mini-USB port hidden on the back. The phone app will also give you a low charge prompt to make it even less likely that you'll be left in the dark.

See.Sense Ace rear light

The flat face does mean that side-angle brightness is lower than we'd like (Image credit: Guy Kesteven)


All-round and long-range visibility isn’t as good as See.Sense’s numbers suggest and we’d like to be able to switch off the traffic sensing modes for group rides but otherwise, the See.Sense Ace packs an amazing amount of genuinely useful smart features into a bright, compact and very user-friendly light, particularly for around town. 

Even if you only use some of the features, it's still very good value, especially if you buy one of the See.Sense bundle options.

Tech specs: See.Sense Ace rear light

  • Price: £44.99 / €52.47
  • Weight: 37g (29g light + 8g bracket)
  • Power: 125 Lumens max
  • Run time: 10 hours on Flash
  • Battery: N/A
  • Sizes: 58mm high, 32mm wide, 19mm deep

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