First Look: The 4iiii Fliiiight Smart Trainer


Remember back in May when 4iiii announced the acquisition of STAC the company (which made trainers and aero/fit stuff)? And remember when they hinted that they’d have a new trainer product in time to show at Eurobike?

No? Ok, well, I did. And more importantly – so did 4iiii and STAC. And true their word they’ve got a new trainer product to show at Eurobike, the Fliiiight trainer. Yes, again, there’s four i’s in there. My keyboard already hates me enough after the last 24 hours.

Now if you put on that memory hat again you might remember that STAC’s past trainers have been unique in that the resistance is done via magnets that don’t actually touch your rear wheel, but rather generate forces to resist it. As such, there’s zero sound from the trainer itself, with the only sound coming from your normal bike drive chain (which in this case mostly depends on how clean you keep it).  Their concept carries through to Fliiiight , except now with a far easier setup/configuration, and no more need for wheel weights.

Here’s the quick overview video:

[embedded content]

Got all that? Let’s dive into the tech specs of the updated version.

Tech Specs & Initial Ride:

The best way to sum up the entire 4iiii Fliiiight is in three words: Not complicated anymore.

Alternatively: Not convoluted anymore

Further: Not fugly anymore

I’ve gotta believe that when 4iiii/STAC sat down to build this iteration, they looked at their top complaints by users and reviewers and simply checked through them all. The previous version was complicated and convoluted to setup. Not hard, but just prone to plenty of places it could go wrong. And when it went wrong – then people had a bad setup. I remember the first time I tried it out on their unit at the show floor and was like ‘Woah, this is so much better than my setup at home!’, after which we talked through the nuances of that setup process for their unit versus what I did wrong. Once I went home I was able to replicate it.

So to start, the entire system now has this crazy robotic automatic calibration ‘thing’. Seriously, the entire back half of the trainer has an internal motorized slider than moves left and right independently (the two arms), and then figures out where your wheel is (independently) and shifts in real-time to match your wheel and the sub-second variations of your accelerations (For real: Just watch the video).


But it gets more fascinating than that. They’re using an optical sensor affixed to the tips of the little poles near your rear wheel to measure acceleration so that they can adjust for it in real-time on resistance.


All you do is place this small white straw/sleeve bit on your spoke, and it uses that as the reflector:


Next, if you actually watch the system in the back, it ‘pulses’ in and out dependent on your cadence. One of the things 4iiii says this addresses is the sub-second changes that you output on the wheel-speed, which in turn means the entire thing feels smoother since the system can compensate on it constantly and instantly. But how does it feel? More on that in a second, first, some tech specs.

So let’s run through the key tech specs:

– Price: $599USD, October availability
– Wheel-on trainer, requires metal wheel (not carbon frame)
– Portability: Yes, with 2hr built-in battery if you want
– Max Resistance: 2,200w
– Max Incline Simulation: 7%
– Accuracy level: +/- 1%
– Trainer Control: ANT+ FE-C & Bluetooth Smart FTMS
– Power Transmission: Both ANT+ & Bluetooth Smart open power signals
– Cadence Transmission: Yes
– No more wheel weights needed

So why aren’t wheel weights needed? Well, previously the wheel weights served to increase the flywheel weight which in turn increased road-like feel. It was also to negate the lack of precision on the magnetic resistance aspect constantly changing. In other words, it provided smoothing. But with the fast resistance changes, they can do it all magnetically.

Actually, before we talk about ride feel – it’s actually a portable trainer that’s viable for warm-ups at races. That’s because it has a battery built into it, which gives you about 2 hours of ride time if needed:


And, in a signal to the rest of the industry to ‘catch-up’, they went with power via USB-C. In fact, it goes one step further, it’s got a trip-friendly detachable magnetic USB-C cable included with it. Kinda like the old MacBook chargers (you can also buy this cable for your newer MacBook or USB-C device). So if you trip over it, the cable part simply detaches and nothing is broken:




Now back in the STAC/STAC Halcyon days this trainer was more well suited towards ERG, given it’s slightly lower incline resistance, and slightly less road-like feel. In some ways, that stays the same. The unit tops out at 7%, which is lower than most trainers of this price point. At the same time, my guess is that you’ve never bothered to change your Zwift ‘Difficulty Level’ setting from the default of 50% (on purpose or otherwise). So that means that any 14% grades in Zwift actually become 7% grades from a trainer feel/resistance standpoint. And again, almost nobody (except apparently me) changes it.

So since there are almost no grades above 14% in Zwift, then the 7% limitation of this trainer probably doesn’t matter too much in practice for most people (unless you like climbing up simulated hills with full resistance, in which case this isn’t the trainer for you).

That takes us to the next bit: Road-like feel of the Fliiiight.

It’s kinda-ok. It’s not bad, but it’s not fantastic, and the other units at $599 have better feel. Still, I’ll defer judgement till the final software/hardware version. There’s some software tweaks they want to make – which can and likely will impact road-like feel, since everything about this trainer is driven by the software and how efficiently and correctly it can move the magnets (including positioning).

Right now 4iiii says that the final version of hardware should be wrapped up in the next couple of weeks at most, and then they should be ready to start shipping in October.

Of course – as with the Fliiiight, the main appeal of the trainer is simply the silence, as well as lack of vibrations. There are none of either. So the only sound you’ll hear is that of your drive chain, and for apartment dwellers that may have thin floors or walls – there’s no vibrations from the trainer, since your rear wheel is just floating spinning in air, not physically rubbing/driving against anything like a typical wheel-on trainer or direct drive trainer would. Or perhaps, folks looking for a light and portable solution to take to races that can still throw down some serious power in a structured workout.



I’m happy to see 4iiii/STAC listened to all the feedback about their previous generation units, perhaps most notably starting with the looks of it. Gone is construction cone orange, and in comes a sleek black unit. Sure, it’s not as flashy, but it’ll more easily blend into peoples apartments and living rooms without folks avoid that portion of the room like a public works project.

On the technology side, the new robotic alignment system is simply cool to watch. I mean, sure, it’s more accurate and all that jazz…but let’s be honest: Everyone is entertained by crazy robots. Still, it does serve a purpose: Accurately configuring your wheel for each use, and then being able to track your wheel in real-time as it rotates. All of that means that gone are the days of finagling with the sensor (hopefully). And getting rid of the wheel weight fiasco is also much appreciated too – it means you can use your bike wheel more easily inside and out (versus before you mostly just left a secondary wheel with the weights on it).

Of course, the downside to the trainer is that the road-like feel isn’t super high-end at this point. There’s also the limitation of needing some form of metal rim on your wheels. If you’ve got fancy carbon race wheels, those won’t work. Though given virtually every bike you buy comes with a set of basic metal-rimmed wheels, I suspect most athletes have a set somewhere around.

Ultimately, I’m looking forward to testing out the final version of this, hopefully later this month. I’ll circle back then or early October with a full in-depth review once that happens.

With that – thanks for reading!

Heads up: You can pre-order the 4iiii Fliiiight via Clever Training. Doing so helps support the site here, and you can use DCR Reader Coupon Code DCR10BTF to save yourself 10%, plus of course free US shipping. Thanks for the support!