YT Decoy MX Core 5 | Electric Mountain Bike of the Year contender

Setup

Unfussy suspension helped make setup easy.

For my 75kg kitted-up weight, I inflated the fork’s spring to 98psi and installed three volume-reducer spacers. I fully opened all the external rebound and compression adjusters.

I put 196psi in the rear shock after consulting my test notes the last time I tested a Decoy and, like the fork, also opened all the external damper adjustments.

I was happy with these settings and they remained unchanged for the duration of testing.

Thanks to the sensibly specced DoubleDown tyres, I used my preferred pressures (24-26psi front, 27-29psi rear) without fear of puncturing.

YT Decoy MX Core 5 climbing performance

The seat tube angle feels slack, especially when ridden back-to-back with bikes with steeper angles. Whether that’s an issue for you will depend on quite a few factors, so indulge me for one minute.

A large chunk of that slackness can be mitigated by dipping your saddle’s nose down and moving it as far forward in the seat clamp as you can. This steepens the effective seat tube angle and helps place your hips over the bottom bracket.

But tackling a steep incline increases the amount of weight over the rear wheel with a corresponding lightness at the front.

Turn the technicality dial up one or two notches and control is quick to get away from you.

Running the seat at full height – which moves your hips even further back compared to a lower position – makes you feel stretched-out; your backside is a long way rearwards, which causes your shoulders to sink towards the bar.

While aggressive and great for maximum effort, when you need some extra bandwidth – such as increased joint articulation – to hoof the bike up and over obstacles, that stretched-out position does little to help.

I found myself busy trying to compensate and get over or in front of the cranks to pick up and move the bike from one line to the next. This leaves little in the tank for any sprinklings of inspired line choice, grip management or keeping the front wheel on the ground.

Turn the dial back to gentle fireroad ascent and you needn’t worry; the Decoy is as comfortable as any other bike; if this is your kind of riding, ignore the above.

If you’re likely to tackle technical ascents as much as gnarly downhills, a bike with a steeper seat tube angle will serve you better.

Shimano Deore XT M8150 Di2 Hyperglide+ performance

Di2 HG+ is a great performer, if a little confusing to start with.

Using the app to set your cadence, shift and other preferences takes a while to learn, but once you find your perfect settings, it's very good.

Gear changes are swift and responsive, and the time between button push and derailleur movement is seriously quick.

Shifts, as long as you don’t mash the button multiple times, are crisp and smooth. While SRAM has certainly taken the on-power shifting crown with Transmission, Di2 HG+ is nipping at its heels.

Unlike SRAM’s timed shifts, which have been criticised as too slow by many, when you want to dump Di2 HG+’s gears the derailleur will respond dutifully and instantly, shifting as many cogs as you command.

While great in theory, if you try to change too many gears too quickly – which is all too easy to do without the physical cabled connection between derailleur and shifter – chain jams between the upper jockey wheel and cassette are frequent.

Care is needed to avoid making a mess of your drivetrain with over-exuberant shifts.

The shifter’s design is the perfect electronification of a manual model. The buttons are the same across both designs and the tactile feedback is firm but not hard. Top work here, Shimano.

Motor performance and battery life

The EP801 motor has plenty of power – kicking out 600W and 85Nm – but it’s only delivered between certain cadences. The harder you pedal, the less assistance it gives – regardless of how you’ve got it tuned in the smartphone app.

Delivering its power naturally rather than rewardingly, which is great for feeding in grip and control on technical climbs, it’s not the same ebike joyride you get from a Bosch motor.

The large 720Wh battery – while bulging beneath the bike’s down tube – delivers good range. Using solely Boost, I managed to exceed 1,200m of ascent on a single charge. Although, once again, compared to Bosch’s 750Wh Performance Line CX, battery life isn’t quite as good for the amount of power you get.

Once you’ve run out of juice, the Di2 gears still shift when you tell them to, but the Free Shift function ceases to work.

YT Decoy MX Core 5 descending performance

Downhill, the Decoy’s demeanour is impressive.

The Tall bar instils confidence in steep, gnarly tech. Weighting them only creates more grip and control, rather than a nail-biting over-the-bar roll of the dice.

442mm chainstays and an 817mm front centre keep your weight relatively central. While the 469mm reach is closer to a size-large than the bike’s XL moniker, combined with its other figures it helps provide plenty of stability.

Little rider input is required to keep it on-line; it’s inert when provoked by repeated stutter bumps or undulations, insulating its rider from distracting inputs.

Sitting pretty and remaining still and controlled, it saves you from doing the legwork to calm things down.

Created by one part geometry, the other suspension, even through roughed-up chunder, the bar and pedals remain level with the horizon.

It tracks your chosen line with laser-guided precision, regardless of the type of terrain you’re rolling over. The excellent Crankbrothers Synthesis wheels play a significant role here, combined with the frame and suspension.

Plenty of rear-end progression eats up large bumps and hefty hucks to flat without incident, but also provides a wicked amount of mid-stroke support.

Its geometry remains composed and still in high-load berms, unwavering in the face of compressive forces.

This predictability gives a chilled and easy-to-ride vibe, emphasised by just how smooth and supple its beginning stroke is; the Decoy fades into the background, leaving you to focus on shredding.

While Di2 shifting performance is great on the way up, downhill its freewheel-focused automatic gear selection proved to be a surprising delight.

On undulating trails with ever-changing speeds, nine times out of 10, it had selected the right gear when I was ready to pedal. This was arugubly better than SRAM’s technology of the same ilk.

The main downer, however, is the Hyperglide+ Di2 variant won’t change gear automatically when you are pedalling. This strange scenario means you have to think some of the time and take your brain out for the rest.

At times, it leaves you lost in a cloudy 12-gear soup as you try to figure out which gear you're in, and whether you have to shift or not.