YT’s contender for best trail bike on the market is the acclaimed Jeffsy, and the flagship bike in the Jeffsy line is the Uncaged 6. Why uncaged? Well, not only is it YT’s maxim on how to live life, the Uncaged tag helps distinguish this special edition model from the Core bikes that make up the rest of the range.

Flight Attendant adds bulk, but being wireless means the overall bike stays looking clean and sleek.

So what makes Jeffsy Uncaged 6 so standout? For starters, it gets the brand new RockShox Flight Attendant electronic suspension, that automatically toggles the suspension settings on the fork and shock between open, pedal and lock modes based on the pitch of the bike, suspension data from accelerometers on the fork and shock, and whether or not you are pedalling.

And, just like the SRAM XX1 AXS drivetrain and the RockShox Reverb AXS dropper post adorning the Uncaged 6, everything is wireless so it can in theory be fitted to any bike as a kit because unlike Fox’s Live Valve there are no dedicated mounts or cable routing required. And because it’s all designed under one roof, the derailleur, seat post, shock and fork use the same battery and charger. So let’s say your dropper post runs out of juice mid ride, simply swap the battery with the shock which then defaults to the open setting and continue as normal. Only the crank sensor uses a AAA battery, which SRAM says should last for a year before needing replacing.

Everything Flight Attendant is controlled through either the fork cap or the phone app. Adjustments are easy to make and serve a useful purpose.

The Control Module on the fork is the brain and user interface of the system, but you can also make all of the adjustments through the SRAM AXS app. You can control the bias of the suspension, with five settings: that run for more open to firmer. So if you have a bike that uses a suspension system that is designed for pedalling efficiency, you’d run the bias more open. You also use the Control Module or the app, to electronically adjust the low speed compression damping on both the fork and shock, while air pressure and rebound damping in are adjusted the old fashioned way.

Based around the same full carbon Jeffsy frame that comes on the Core 4, the Uncaged 6 boasts 152mm of rear travel in the high geometry setting and 147mm in the low position. Where YT splits the difference and calls it a 150mm bike. But just like the alloy Jeffsy Core 2 that we featured in our Trail Bike of the Year test, we measured rear travel at 140mm in the low setting, so 7mm shy of claimed. The suspension is so well tuned though, that you never feel under gunned.

RockShox’s new ButterCup footnuts include a rubber bushing to reduce vibrations

Suspension

If the addition of Flight Attendant isn’t enough to get your pulse racing, how about the latest fork tech? The new RockShox Pike, Lyrik and Zeb Flight Attendant equipped forks now feature Pressure Relief Valves on the back of the lower legs for blowing off steam, just like the latest Fox forks. It’s what’s inside the 150mm travel Lyrik Ultimate on the Jeffsy Uncaged 6 that makes the biggest difference to performance though. By adding vibration damping material between the fork lowers and the air-spring and damping pistons, RockShox can tune out some of the high frequency vibration that’s beyond the operating range of the damper. Dubbed ButterCups, RockShox claims that their addition blocks up to 20% of unwanted trail chatter. And while we have no way to verify that claim, the proof is in the pudding right? So given that the new Lyrik Ultimate feels and sounds like you’re running a softer compound front tyre, we’ll take ButterCups all day long.

Paired to the Lyrik is the RockShox SuperDeluxe Ultimate Flight Attendant RCT3 shock. Like the fork, spring pressure and rebound damping are set in the traditional way, where the rebound dial is partially obscured by the shock reservoir, Flight Attendant unit and battery. Sag gradients on the shock body take the guesswork out of the initial set up, but the shock stroke measured a couple of millimetres shy of the claimed 55mm, which would explain why the Jeffsy came up short on travel.

Components

The buzz of a freehub can split opinion. For some riders the louder the better, while others like it to go unnoticed. With the Industry Nine Hydra freehub on the CrankBrothers Synthesis Carbon Enduro wheelset, every ride on the Jeffsy Uncaged 6 feels like you’re the star of the latest Rupert Walker Raw 100 edit. We can only dream, right? Factor in the front and rear specific rim profiles, spoke counts and spoke thickness, and the Synthesis wheelset offers increased stiffness and strength on the rear with a more compliant ride up front.

The left hand AXS remote controls both the Reverb dropper post and the Flight Attendant modes for hands-free adjustment

In keeping with Gucci build, SRAM’s wireless XX1 AXS shifting provides a precise, ultralight shift action that’s not impacted by the cable routing or weather conditions. The same goes for the RockShox Reverb AXS post. Our only gripe being that it comes stock with 150mm drop, but we could easily have run the 175mm option as we had 30mm of post poking out above the seat collar.

As with all of the top-end YTs, Renthal takes care of the cockpit, the 800mm Renthal Fatbar Carbon and Apex 50mm putting the rider in a very commanding position. Yes, 800mm is wide for a trail bike but hey, that what saws were made for.

In the case of the YT Jeffsy, Flight Attendant has turned a good bike into a great bike

Performance

Knowing when the rider is pedalling is game changing for Flight Attendant. Because when pedal inputs are combined with pitch detection and the vibration sensors on the fork and shock the Control Module gets a more complete picture of what’s actually happened on the trail. As such, Flight Attendant can make better decisions about how the suspension should respond in any situation. It helps too, that there are three suspension settings rather than two, so the response can be fine tuned to a much broader range of scenarios. And we should point out that lock mode is not a proper lockout, and as such, feels very similar to the firm setting on Fox Live Valve equipped Giant Trance.

Play on the descents, power up the ascents: Flight Attendant lets you save more energy for the fun stuff.

Taken together, Flight Attendant isn’t as binary as Fox’s Live Valve system and offers a much wider range of base line suspension set-ups – the Jeffsy comfortably running anywhere from 25-30 per cent sag without any quirky traits. Infact, even when we were actively trying to trick the system, it always seemed to be one step ahead. And therein lies the beauty of Flight Attendant, it’s working tirelessly behind the scenes but actually has a noticeable impact on the performance of the bike. On the Jeffsy Uncaged 6 Flight Attendant make it more efficient during hard pedalling efforts and while spinning up climbs without eroding any of the bike’s suspension performance.

No matter whether you’re climbing, descending or jumping, Flight Attendant is always in the right mode and never does anything quirky.

How much more efficient Flight Attendant makes the bike is hard to quantify, but your brain picks up on it instantly, so your enthusiasm for pedalling when you’d normally take it easy is off the chart, which is evident as your aching quads after every ride. And if you’re in any doubt about the benefits of Flight Attendant, there’s an override option, that you can preassign to lock, pedal or the open setting and it’s accessed with the second button on the AXS left-hand controller. We assigned it to the open setting just to see what its like riding the same trails with it off, and guess what? The bike felt the same on the descents and less efficient everywhere else. So you actually miss it, even though you didn’t really notice it in the first place. Strangely, the addition of Flight Attendant also made the size L Jeffsy feel bigger than the numbers suggest, and we suspect this is due to the bike feeling more stable overall. And compared to the alloy Jeffsy Core 2 that was in our Trail Bike of the Year test, the overall feeling of the Uncaged 6 is stiffer and more direct, due to the carbon wheels and full carbon frame. Yes, we still had a little bit of heel rub on the stays but it’s something we quickly adjusted to.

Four key points

• 10 low-speed compression settings on the RockShox fork and shock are adjusted electronically
• Full carbon Jeffsy frame has size specific geometry, where the XL and XXL sizes have 5mm longer chainstays
• Maxxis EXO casing tyres with the MaxxTerra 3C compound are a great choice for trail riding.
• The 150mm travel RockShox Lyrik Ultimate Flight Attendant fork features Pressure Relief Valves and ButterCups