Lezyne Strip Pro Ai Alert 400+ Rear Light

The Lezyne Strip Pro AI Alert 400 is a very nice rear light that's easy to fit and pushes out some serious lumens for a long time, as well as packing a decent braking function. So long as you don't take the AI claims as seriously as Lezyne does it's a solid investment. And it's right up there with the offerings in our best rear bike lights buyer's guide.

Let's dive into the AI bit first shall we? Clearly a £60 light isn't doing real-time machine learning of how you ride and it isn't adjusting its braking function on the fly to match your riding style: the light's documentation specifically says that it's not collecting rider data. So what is going on that deserves a big 'AI' sticker on the side?

Well, Lezyne told us that it collected over 1,000 hours of riding data on the light, including speed, accelerometer and braking actions and fed all of that into a machine learning algorithm that tried to make sense of what braking looks like, and when the 150-lumen flashing brake light function should be activated. The idea is to move away from simple on-off accelerometer-activated braking and cut out some of the false positives.

And does it work? Well, it detects braking, quite a lot of the time, and you can't trigger it by shaking it with your hand in the shed, so yes: it works. The usual provisos about other road users being able to interpret a change of light pattern as a braking action apply here.

I spent a fair bit of time with my light on the bar (so I could see it) and tried different types of braking – slow, sudden, juddery – and the light is best at picking up strong braking and a bit more intermittent when the signals aren't as clear.

I tried it on my seatpost and also on my seatstay – the silicone strap is pretty versatile and aero seatposts are no problem – and anecdotally I'd say that it works better when it's upright. At a bit of an angle on the seatstay it was noticeably less likely to trigger.

I'd say it's probably a bit better than a simple accelerometer circuit. I wouldn't necessarily say it's 'the next generation in cycling light safety and visibility' as Lezyne confidently claims.

Aside from all that, though, what it definitely is is a really good rear light: there's loads to like about the unit itself. For a start it's IPX7 waterproof, which is really the gold standard for a bike light: I'd have no qualms about fitting this to a bike with no mudguards and heading out into the rain for hours.

The light itself has a wide 270° field of visibility and the 400-lumen day 'highly disruptive' flash mode is really, REALLY bright. As is always the case with Lezyne lights you get a big selection of modes, seven on this unit, all the way down to 5-lumen Femto mode which it says will last for 80 hours; I got bored waiting for it to die after a couple of days. Even on its 80-lumen constant output, which is a lot of rear light, you get five and a half hours of runtime from the 1900mAh battery.

I used this light on a 25-hour, 400km audax with more than half of that in the dark, and never got close to running it down even though it was on in some mode or other all the time.

If I was the kind to slap on some tribars to try to beat my ten time on a dual carriageway of a Saturday morning, then it would also be a good pick for that thanks to that day flash mode. And everything in between, really: short of hillclimbs where you might baulk at the 71g weight, this is a light that's very easy to recommend for all types of riding.

Value

It's fairly expensive but not the priciest we've reviewed.

The most comparable light is probably the Ravemen TR500, which costs about the same.

The Exposure Boost-R will cost you half as much again. You can have this light without the AI braking tech but for an extra fiver on the list price it's worth having.

Conclusion

The AI tag may not be totally warranted but this is still a very high-quality rear light that's easy to fit, bright, impressively waterproof and with great running times. What more do you want from a rear light?

Verdict

Excellent rear light you could use for any type of riding, with good braking function