The Cateye Rapid X2 Kinetic has a sensor designed to make it act as a brake light for your bike. In terms of build quality and the features you'd want from a rear light, it's a good design, so it's a crying shame that the brake light element is so sensitive as to be not fit for purpose in real-world applications.
The ability to signal to other road users that you are slowing down is, generally speaking, a good thing – it allows them to react sooner, reducing the risk of collision. Over the years various firms have tried to bring this functionality to the lightweight, minimalist world of the bicycle with limited success – varying from the frankly awful Sigma Rear Brake Light to the 4.5-star Lupine Rotlicht and See.Sense Icon. Now the 800lb cycling accessory gorilla has waded into the smart rear light market with the Rapid X2 Kinetic.
Physically, and in brightness, flashing modes, charging, run-time and most other aspects, the Rapid X2 Kinetic is identical to the recently reviewed Rapid X Rear. The only difference is that instead of being able to manually choose the 50-lumen high mode, it only comes on for 2.5 seconds when the accelerometer detects you are braking.
So the question must be: for an extra £13 over the Rapid X, does the X2 Kinetic actually work? Yes. And no. It's complicated.
On smooth or rough roads, fast or slow, going uphill or down, the brake function would activate. Unfortunately, it would also do so when accelerating or riding at a constant speed. That's not to say it didn't 'work' – when decelerating under braking, the brake light came on every time. The problem is the false alarms.
You could argue that any light is better than no light, but when the proposition is that you advise other road users of your deceleration, any incidence of false alarms is not going to deliver the desired reaction from them. If you're in a bunch ride and those behind realise your light is going off at random intervals, they won't trust it. A following driver will wonder what on earth you are doing – that it's simply an erratic flash.
I tried mounting the X2 Kinetic in a number of locations – rear of the fork, seatstay, seatpost, on different bikes and at different angles – all with the same fundamentally random results. In all cases even moderate braking would trigger the 50-lumen mode – but also minor and major bumps and changes in orientation would as well. To me, this fundamentally undermines the USP of a 'brake light'. Plus, with no option to manually select the brightest 50-lumen mode, in effect you're getting less light for more money.
As the form factor, installation, battery life and brightness are all winners, hopefully Cateye will release an updated version with a more reliable accelerometer to deliver on the promise of a functional, reliable brake light. Until then, I'd suggest you look at the Rapid X.
A good light but it doesn't deliver on the promised reliable brake light functionality
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road.cc test report
Make and model: Cateye Rapid X2 Kinetic
Size tested: 3 modes: Constant / Flashing / Rapid * Up to 50 lumen output
Tell us what the light is for, and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?
It's for people who want a rear light that advises others that they are slowing down.
Cateye says: "It's time for road safety to run 'round the clock. Introducing the Rapid X2 Kinetic, a movement-sensitive, day and nighttime light for your ride.
"The Rapid X2 Kinetic is a 50-lumen, USB rechargeable safety light that mounts easily on your seatpost. A built-in accelerometer automatically switches into a constant burst mode when it senses a sudden change in speed. Similar to daytime running lights on an automobile, the Rapid X2 Kinetic helps make your presence known as a cyclist. 180 degrees of visibility allows you to be seen from varied perspectives.
"A Battery Auto-Save feature makes sure you're covered the entire ride by automatically switching to a flashing mode should the battery run low. With up to 30 hours of runtime, the Rapid X2 Kinetic ensures you'll be drained from your ride long before your light is."
Other lights in the Rapid range offer different modes and brightnesses, but the Kinetic eschews these in favour of the technology to act as a brake light.
Tell us some more about the technical aspects of the light?
* 3 modes: Constant / Flashing / Rapid
* Up to 50 lumen output
* Fixed beam from pulse when stopping
* COB LED technology
* Li-Polymer battery
* 180 degree visibility
* Complex circuitry allows safe charge and discharge
* USB recharge (2 hrs)
* O-Ring attachment
* Battery auto save
* Low battery indicator
* Light mode memory
Spacer X accessory allows the kinetic2 to be mounted on the standard clip-in Shimano light mount. There is also a deep aero rubber option for aero seat posts.
It's Cateye. That means excellent.
Very easy to use. No issues here.
Really liked the simple rubber band mounting. Solid and fast.
It goes for ages: 17 hours on the rapid flash will see anyone through a week's riding.
Conflicted. It's a brightish light and lasts forever, but doesn't do what it says. Sort of.
Looks and feels solid.
Not much at all.
Pretty poor given it fundamentally doesn't deliver on its main objective. Pricey as a straightforward rear light.
Tell us how the light performed overall when used for its designed purpose
Not well at all. Too random to be relied upon.
Tell us what you particularly liked about the light
The form factor. Slim, easy on-off. Nice.
Tell us what you particularly disliked about the light
The randomness of brake activation.
Did you enjoy using the light? Yes
Would you consider buying the light? No
Would you recommend the light to a friend? No
Use this box to explain your score
I have to rate the Kinetic X2 as below average. It's 'poor' in the context of other brake lights that do work, and it's pricey; otherwise I'd agree with the review of the Rapid X light, that it's a 'good' package – but not for £50. See? Conflicted.
About the tester
I usually ride: Merida Ride 5000 Disc My best bike is:
I've been riding for: Over 20 years I ride: A few times a week I would class myself as: Expert
I regularly do the following types of riding: cyclo-cross, club rides, general fitness riding, mountain biking, Dutch bike pootling