While YT claims that the Jeffsy is "the most aggressive trail bike on the market," I don’t quite agree. However, what I do believe is that it’s an incredible bike and, as such, is the worthy winner of our 2018 Trail Bike of the Year test.
- The YT Jeffsy 29 CF is one of our Bike of the Year bikes for 2018. To read reviews of the other contenders and the categories tested across road, mountain and women's bikes, visit our Bike of the Year hub.
On paper, the 140mm travel Jeffsy 29 doesn’t necessarily stand out. The geometry is dated and the kit, while good, has some slightly left-field choices — some work well, some don’t really add much over the kit you might expect to see normally. Fortunately, few actually detract from the ride. But YT proves that a bike is more than the sum of its parts and they’ve been combined here to make one of the most fun bikes available on the market.
The frame is a full carbon affair, with smooth lines and a well-chosen aesthetic that has found favour with everyone who’s seen it. The suspension linkage follows a regular four-bar design with a horizontal shock placement, and a rocker link that merges smoothly between the front and rear triangle. Cables sit on top of the down tube, aiding easy home maintenance.
The frame doesn’t come with the latest metric length shocks. I’d have expected a Deluxe here from RockShox most likely, but it comes with a Monarch RT3 in the previous sizing instead.
I don’t have any issues with this being the case, because the Monarch is a fine-feeling shock with decent damping and plenty of tuning issues, and it shouldn’t be a turn-off if you’re looking to buy the Jeffsy. Fortunately, it does come with Boost spacing now, which is a standard that has a subtle, but noticeable difference in feel.
There’s a flip-chip to adjust the geometry slightly, although throughout the test I left the bike largely in the low and slack setting because, well, I'm yet to find a bike that’s better in its tall and steep setting.
The geometry is a little short, with a reach of 445mm in the size Large frame. This is balanced with a 440mm chainstay in the Large and XL (the Small and Medium frames get a 435mm stay).
A 67-degree head angle sticks the 29in wheel out front, while the 74.5-degree seat angle is bang in the middle of the range I’d expect to see. The 32mm bottom bracket drop is bang on the money, but the 480mm seat tube length is perhaps a touch longer than ideal, depending on your proportions.
This seat tube length does make it a touch trickier to upsize the frame, should you wish to get a longer reach. At six foot, I had to pretty much slam the post in the frame to get the saddle height right on a Large.
While the back end is controlled by a Monarch RT3, the fork is a Pike RCT3 with 140mm of travel. The bike rolls on a pair of e*thirteen TRS wheels wrapped in e*thirteen TRS+ tyres in 2.35in width. The drivetrain uses Shimano’s XT shifter and mech with an e*thirteen TRS+ cassette with a 9-46t range, driven by a Race Face Turbine crankset.
Race Face also provides the cockpit with a Turbine R bar and stem combo. A SDG Fly MTN saddle sits on a TRS+ dropper post.
The TRS+ cassette is an interesting proposition. The 9-46t range is wider than the 12-speed SRAM Eagle groups found on many bikes the Jeffsy competes against, though obviously it has one extra gear ratio to play with.
The 9t isn’t quite as smooth feeling as a 10t on the Eagle cassette, nor is the shifting quite as smooth across the block. You’ll also need to give the cassette a smear of grease now and again to keep it running quietly.
However, I like the feel and reliability of the Shimano XT shifter and mech, so this in combination with the wide range is a fair addition to the bike.
YT Jeffsy 29 CF on the trail
Put the Jeffsy on the most demanding of tracks and some of the ‘issues’ with the frame’s geometry become apparent. The shorter than average reach makes it a bike that’s not quite as stable and composed as some, certainly if you’ve had to pick the size based on the reasonably long seat tube.
Likewise, if the bike was to be ‘better’ in the steeper, rougher tracks, a degree or two off the head angle wouldn’t go amiss.
I also found on some of the bigger hits that the suspension doesn’t have quite the same bottomless travel feeling found on some of the other bikes that competed in Trail Bike of the Year 2018.
In reality, though, if you regularly ride these tracks — and we’re effectively talking DH and EWS tracks here — you’d be better off on an enduro bike anyway.
On the trails (which I reckon this bike will spend most of its life) it's an absolute hoot.
Yes, I like longer, slacker geometry, but the shape of the Jeffsy means it’s highly manoeuvrable both on the ground and in the air, and with light handling it's super happy to sling its way through corners. The numbers the bike has wouldn’t have been out of place three years ago and bikes were still fun then, right?
Up front the TRS+ tyre has a soft compound that cuts nicely into soft dirt and mud, and grips well on rocks and roots. On smooth, hard-packed berms the shoulder knobs are prone to folding, giving a slightly vague feel, but they do grip.
It’s not a tyre you see often on production bikes, probably because it’s arguably not the best all-rounder, but if you ride in the woods a lot you’ll appreciate it.
At the back the tyre provides acres of grip on loose climbs and during braking, however it's a bit of a drag on smooth climbs.
As you’d expect from the top-line Pike fork, the control offered to the front wheel is exceptional; the damping is spot on and the chassis is a perfect match for the kind of bike this is. The bars are reasonably stiff, but the combination of the tyres, with their decent volume, and the fork remove any noticeable harshness.
The rear suspension gives the bike a real poppy, playful feel, which really promotes the Jeffsy’s character. Point it at a rock or root and you’ll quickly find yourself gapping to the next smooth section, because the bike just encourages you to spend as much time in the air as possible.
If you hit really choppy stuff quick, the back end can get overwhelmed a touch, but if the back end is packing down a touch the low bottom bracket and grippy tyres give you enough confidence to hold on until things smooth out a bit.
This raggedness can even, dare I say, be part of the bike’s appeal. It does, however, reward finesse and precise guiding through the rougher stuff.
While the rear tyre is draggy, the Jeffsy isn’t too bad at getting back up the hills. There’s a Pedal mode on the shock for off-road climbing and a lockout if it’s smoother.
The seat angle gives you a reasonable position over the cranks, though that shorter reach means it isn’t the roomiest of bikes. It’s not going to aid you in quests for KOMs, but this bike really suits the kind of rider who wants to pedal up socially, then have maximum enjoyment on the way back down.
YT Jeffsy 29 CF overall
I rode well over a dozen bikes for the Trail Bike of the Year category in 2018's Bike of the Year, covering everything from bikes that could be competitive at your local cross-country race to ones that wouldn’t be out of place in an enduro race.
The Jeffsy just squeezed into the top spot simply because it was the most fun bike in the test to ride (assuming you get your kicks from having a laugh, rather than just going flat-out everywhere).
The Jeffsy is okay at climbing, doesn’t feel slow on the flat and through the turns and can handle big descents. It’s also hilarious to ride. It encourages you to pop off the next root in the trail, try to gap rocks and scandi-flick round the upcoming corner.
With a component package that can just about cope when things do inevitably get out of shape, you’re sure to have had a blast each and every time you ride it. And that’s why the YT Jeffsy 29 CF is our Trail Bike of the Year.
If you're looking for alternative options, have a look at the following list. Each bike has been thoroughly tested and robustly reviewed. Click on the links for the full review.
- Norco Sight A2 29
- Trek Fuel EX 8 29
- Canyon Spectral CF 9.0
- Orbea Occam TR H10
- Marin B17 3
- Transition Scout NX
- Commencal Meda TR V4.2 Essential
- Santa Cruz Tallboy Alloy R
- Juliana Joplin R
- Specialized Rhyme Carbon Comp 6Fattie
- Canyon Spectral WMN CF 9.0 SL
- Yeti Beti SB5 C-Series XT
- Scott Contessa Spark 910