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21g £ 39.99

The Sigma BC 9.16 ATS Computer is an 11-function wireless model, which, according to the blurb “the ideal computer to improve fitness”. In my view, it’s a good bet for those wanting proper insight into their training but not wanting to share it with the virtual world. It’s also surprisingly intuitive to calibrate and use. 

Pros: Nice selection of model, easy setup, user-friendly, clear display,

Cons: No backlight, o-ring seal makes battery changes tricky, no low battery indicator.

bicycle cyce velo rad computer wireless


Opening the packaging, I was surprised by just how similar the mounting kit looked to my long serving VDO M3L


However, despite some superficial similarities, the two are quite different. The M3 is “only” 7 functions That said, both head units use the same style mode “bar” at the base, keeping things compact, convenient and uncluttered.

computer bicycle bike wireless sigma

The Sigma has 11 functions in total, consisting of: Current speed, Average speed, Comparison of Current/Average speed (think pacer arrow to keep you on track, essentially), maximum speed, distance, total distance, ride time, total and ride time, clock, calories, and total calories. Now, what’s the ATS stand for then? Well, it basically refers to the computer’s auto stop-start function, giving a two-hour period where it will wake from hibernation, given a few turns of the front wheel.

Perfect for café and other rest stops There have been occasions where I’ve felt a backlight was a missed opportunity but this is easily overcome, using a modestly powerful helmet light, such as this Brightside Topside


In common with the VDO, the package feels very solid, although I was surprised to discover it meets IPX8, which is full blown immersion in real terms. I went this route, tossing the head unit into a bucket of icy water and it never missed a beat, which bodes very well for winter mountain biking. Build quality elsewhere is similarly solid, although their proximity to wet, mucky stuff means sensors lead hard lives, so I gave the battery contacts a precautionary lick of silicone grease.  Oh, and those lamenting the lack of wired units will be delighted to learn there’s a wired version, too.

Mounts/Fitting Kit 4/5


The mounts and sensors feel similarly robust and are as universal, as you’re likely to find. Additional kits are available at £19.99, so you can port the head unit between bikes. The head unit mount attaches to the bars/extension bracket via an adhesive and cable ties, which is reliable. The adhesive is also tolerant of switching around but ideally, select your desired angle before committing yourself. 

cycle bike velo rad cockpitbars

Zip ties are supplied, although the fork sensor can be fitted via rubber O-ring, which might lack the outright security of zip ties but fine for a road bike, and arguably, all things being equal, kinder to paintwork. 

I went the cable tie route, since Ursula is a four seasons’ go anywhere build, Situations where sensor loss is potentially more likely. I’ve also paired ours with the OEM and other, more generic magnets with no discernible loss of performance. Provided you stick to the 3mm distance between them.  In common with my VDO, the bar mount is a very secure host, although intentional removal of the head unit, say when locking up in the street, is similarly faff-free. A gentle rotation of the computer secures release. An audible click also denotes its locked in position, so you’d be going some (or incredibly unfortunate) to jettison it into the path of a bus.

Setup/Functionality 4/5

Setup proved disarmingly straightforward. Selecting things such as language and wheel-size were a cinch, once I had stopped over-thinking things, and just followed the instructions. So long as you’ve chosen your mother tongue of 


seven languages, bargain on 5-10 minutes, tops. OK, a little longer if you’re needing to measure wheel size etc. Otherwise, it's just a question of working through mode and confirm using set. You can also enter the mileage from an old, or expired computer manually, which is a nice touch. Aside from keeping an eye on your training, bike servicing/component replacement intervals are easily stuck to. 

 In fact, the “hardest” thing to configure was the clock and that only took a few minutes.  From here, simply a matter of pressing the big mode button (below) to select the desired interface i.e., whether you want to see your speed and calories burned, current speed and distance etc.

handle bars bike bicycle computer mount

Display/Buttons 4.5/5


The large display window is simple to read, even in relatively low light and around 25mph. Pacer arrows will nag/urge you to up the tempo- again, at once and its similarly easy to see how far you’ve come and whether that flapjack is in order. The mode button is intuitive, working to the same principle as others, including the VDO, so mistakes should be uncommon and attributable to tiredness. A simple, definite prod of the thumb is all that’s needed- no problems wearing full-finger gloves either, although temperatures meant I’ve primarily donned mitts, or liner types.

This is particularly welcome on group rides, or in unpredictable, stop-go traffic. Talking of stop-go, “wake” the unit by pressing the mode button at the start of your ride. Once activated, the unit’s auto sensor will kick in, automatically engaging the computer when it detects movement. There’s a two-hour grace period too, which is great if you’ve stopped at a friend’s/the café' or just parked up to explore.


Reliability/Accuracy 4.75/5

Once upon a time, wireless units were renown for being susceptible to interference and thus, quirky readouts, especially when passing electricity substations, pylons and similarly high voltage scenarios. However, ours hasn’t missed a beat, even when I’ve plonked a heart rate monitor beside it. Again, so long as you’ve set the wheel circumference manually and got the sensor/magnet proximity right, speed and other details are seamless.

Certainly in line with its Cat Eye predecessor along the same loops with identical components and within .5mph of roadside speed detection signage. No 99.9mph readouts when I’ve been grinding up a climb in bail out gear. Staying with speed, I wasn’t surprised to find a slight discrepancy when defaulting to the wheel circumference presets. Don't be lazy, measure properly.  Calories burned, rather like the wheel sizing presets is a guide, rather than gospel but to be expected at this price and still a helpful ballpark. 

Durability 4.25/5

As I said earlier, IPX8 is pretty much bombproof in terms of weatherproofing and composites also feel solid and the bracket’s tenure is similarly reliable, while still permitting easy, intentional release. I managed to lose the rubber O ring seal while changing the head unit’s OEM CR2032 battery.

Even so, with a lick of silicone grease clinging to the battery cover, ours has still shrugged at heavy rain and still passed my garden hose test without missing a beat. All things considered, there’s little to suggest it won’t lead a long and productive life. Talking of batteries, VDO estimate battery life to be around 3,000km. Our head unit’s OEM cell died within a matter of rides, but the budget replacement is still going strong. 


Value 4/5


£34.99 is competitive, especially given the specification and build quality. Cat Eye Strada Slim Wireless Computer offers a good choice of functions but retails at £49.99. Staying with Cat-Eye, their Velo Wireless is a few quid cheaper than the Sigma at £34.99. It also boasts a calorie consumption function, Current Speed, Average Speed, Maximum Speed, Trip Distance, Total Distance, Moving Time and Clock. Those looking for something simpler still may find Decathlon Van Ryssel 500 Wireless Cycling computer worth a closer look. It has eight functions and retails at £24.99.



Minor niggles aside, the Sigma BC9.1 Wireless Computer is a user-friendly model, well suited to novices, yet sophisticated enough to meet the needs of more experienced riders. Those who want an inexpensive everyday computer, without heart rate monitors, cadence or online connectivity. 

Verdict: 4/5 Well made, user friendly computer for those who don’t want or need internet connectivity. 

Michael Stening




Ryton On Dunsmore

Coventry  CV8 3FH


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