YT Jeffsy Core 3 review | Trail Bike of the Year contender

The YT Jeffsy Core 3 sits bang in the middle of a completely refreshed five-bike Jeffsy line-up.

The Jeffsy has long been a popular bike in our Trail Bike of the Year test, with a win under its belt in 2018, and a number of podium spots in subsequent years, even when the outgoing model was long in the tooth.

The Jeffsy has traditionally been a ridiculously fun trail bike, with tons of pop and a low-slung attitude. It's a bike that has always felt as if it loves being rallied around the woods.

This new version of the model sees subtle alterations in geometry and suspension performance. It's outfitted with the latest features we've come to expect, such as SRAM's Universal Derailleur Hanger and down tube storage in the carbon models, which includes my test rig.

This carbon 29er delivers 145mm of rear-wheel travel and 150mm up front.

The new Jeffsy is still an incredibly fun bike to ride. However, it feels as though the focus has shifted a little towards the longer-travel, enduro-ready YT Capra, with a faster, more planted ride that’s had its poppy feel detuned just a touch.

In some ways, this generation of the Jeffsy feels as though it has grown up a little – it’s up to you whether you think that’s a good or bad thing.

YT Jeffsy Core 3 frame and suspension

I’ve always been impressed with YT’s frame finishing and it’s no different here.

The pivots are all (bar the driveside chainstay pivot) easily accessible from the non-driveside of the bike for easier frame stripping. They receive decent protection from the slop with an additional seal over the standard double-sealed bearings.

The frame’s built to look good for longer, with plenty of protection and a slimline rear triangle to reduce heel rub. The removable down tube bumper even has sound-deadening behind it.

There’s also plenty of carrying capacity.

Elsewhere, there are rivets under the top tube to stash tools, a 620ml bottle is included and there's storage in the down tube.

This is accessed via a smooth-operating, almost water-tight door, revealing neoprene socks to stop rattles, and an in-tube barrier to preventing everything from falling towards the BB.

The latest-generation frame’s 145mm of travel is provided by YT’s V4L 4-bar Horst linkage, with a pivot sat on the chainstay ahead of the rear axle to minimise the influence of pedalling and braking forces on the suspension.

This iteration of the Jeffsy sees 5mm less travel, but, more isn’t always better – it’s what you do with it that counts, right?

As is typically the case with new bikes, the suspension is said to ramp up more at the end of the travel to help deal with the big blows.

YT tells us that the anti-squat is 105 per cent at the 30 per cent sag point, which indicates it should remain fairly neutral when pedalling.

YT Jeffsy Core 3 geometry

Five sizes are offered, with projected rider heights of between 153cm and 203cm.

At 182cm, I rode the size-Large bike.

As has often been the case with the Jeffsy, the geometry is really ‘average’.

This might sound like a criticism, but I mean nothing of the sort. The numbers are all consistent with what a do-it-all trail bike should be.

The reach of 475mm won’t require riders to completely re-address their riding style to make it work, because while it’s not short, it’s certainly not one of the most stretched trail bikes.

A slack-ish head angle of 65 degrees puts the front wheel nicely in front of the bars, contributing to an 810mm front-centre, and the seat angle is just about steep enough for efficient pedalling, without putting excess weight through the wrists or sit bones.

At my saddle height of 750mm, I measured it at 76 degrees, which is quite a bit slacker than the 76.9 to 78.6 degrees quoted across the sizes.

There is a flip chip built into the suspension linkage, which steepens angles by 0.6 degrees and raises the BB by 8mm – for the bulk of my testing I left the bike in the low position.

Chainstays are set at either 437mm (S, M, L) or 442mm (XL, XXL).

YT Jeffsy Core 3 specifications

This mid-level bike might not represent as good value as we've come to expect from YT, but as ever, the kit is all pretty decent stuff.

At the time of writing, YT has reduced the bike to £3,299, making it much better value.

The suspension, from Fox, is Performance-level. This means the 36 fork, with 150mm travel, gets the basic GRIP damper, while the Float X shock is also the most basic of its family. It still gets a lockout lever, though.

SRAM's wireless kit might steal the limelight, but SRAM's mechanical GX drivetrain still shifts well, and does so better than Shimano mechanical kit when coated in UK grime – in my experience.

SRAM’s Code R brakes are powerful enough for a trail bike, too.

Front and rear-specific Maxxis Minion tyres, in suitably tough EXO+ casings, are wrapped around no-nonsense DT Swiss M1900 wheels.

A Renthal cockpit joins an SDG saddle, sat atop the latest version of YT’s Postman dropper, which enables easy travel adjustment of up to 25mm. The Large bike I tested has a 170mm-travel post.

15.3kg isn’t light for a trail bike, but the Jeffsy feels ready for any treatment.

YT Jeffsy Core 3 ride impressions

With simple dampers front and rear, setting up the fork and shock is a quick job – simply inflate to the desired sag level and add a click or two of rebound damping, from fully open.

Then, give it a couple of laps and perfect your setup.

I tend to start with 28 per cent sag at the rear, pop in the recommended pressures on the back of the fork for my weight, and see how it goes.

On a bike like this with decent tyres, I put 21psi in the front and 22psi in the rear, with tweaks to suit the conditions and tracks.

YT Jeffsy Core 3 climbing performance

Though the seat angle at my pedalling height isn’t quite as steep as YT's geometry chart suggests, the Jeffsy still proves a comfortable place to sit, with a roomy front half that doesn’t feel cramped and a pretty decent hip position over the cranks.

That said, on the steepest pitches, the seat angle puts your weight a little further back in relation to the axles. With a 437mm chainstay length, which isn’t super-long, one can feel a little perched over the rear axle.

Fortunately, the anti-squat figures and general demeanour of the bike means it doesn’t sit deep into its travel, or feel particularly wallowy when you’re spinning the cranks.

The Jeffsy strikes a balance between a bike that hoovers up every trail imperfection but feels sluggish, and one that bumps over everything but is ruthlessly efficient.

In many respects, it sits in the middle of the bell curve in terms of how it approaches climbs, which is a plus point in my eyes.

The Jeffsy is comfortable as you rattle it up rocky ascents, with the rear suspension taking the harshness out of rocky ledges. It’s supple enough to help the Minion DHR II eke out traction in loose and muddy surfaces.

At the same time, while it might not set records up your local hill, it doesn’t feel as though you’re pedalling through treacle.

If you want to put a real spurt in, the Float X’s lockout lever is within easy reach. However, its position in the middle of the front triangle makes getting hold of your bottle, located under the shock in the belly of the bike, a little more of a stretch.

The feeling through the cranks is good, too. SRAM’s GX drivetrain is smooth, shifts well under power and shrugs off mud and grit well.

YT Jeffsy Core 3 descending performance

As soon as there’s an inkling of a negative incline, the Jeffsy seems to want to pick up speed.

This makes the bike a demon on trails mellow and manic, ensuring trail-centre laps are just as much fun as steep sessions in the woods.

Both tyres have the thicker EXO+ casing, which you wouldn’t normally consider quite as sprightly as the thinner, lighter EXO casing found on many trail bikes at this price point. Props to YT for ensuring the Jeffsy still has an engaging ride.

The tyres contribute to a feeling of composure over rocky trails, their thicker carcass helping dull impacts.

This works well with the suspension – the Fox 36 Performance is a fine fork.

The GRIP damper contributes to a wonderfully comfortable ride, smoothing the way over rocks and roots effortlessly.

On smooth and steep tracks, I occasionally twisted the low-speed compression dial by a click or two towards the firmer end, just to calm the front end down a touch. It enabled me to push a little more aggressively through the bars to generate speed via pumping the fork, or to offer even more support as the bike entered a catch berm.

The Performance level Float X shock in the middle of the bike is also a smooth performer. It sits nicely in the middle of its travel, quietly getting on with the job of filtering out the worst of the trail noise.

It has an active feel, that deals with each impact as they come, giving a smooth ride that matches that of the front.

Previous-generation Jeffsys have been ridiculously fun to ride, and that pattern continues with the latest version.

There’s still pop and support, but not quite at the same level as the previous bike.

This, along with the active suspension, meant the bike felt more planted over high-frequency chatter, encouraging me to pick up speed, but also offering a little less encouragement to find every lip going.

The Jeffsy is a really easy bike to get on and ride and quickly feel at home on.

Its relatively neutral geometry doesn’t throw up any surprises, and its blend of angles and measurements means it’s super-easy to tip into a turn or slither down a chute.

The head angle is slack enough to give confidence when you’re in the steeps, while at the same time it’s not so slack that it that hinders the bike’s ability to easily twist and turn as it threads a line through the trees.

Though a little longer than before, the chainstays help when you want to loft the front wheel and contribute to its ability to turn on a dime.

How does the YT Jeffsy Core 3 compare to the Canyon Spectral CF7?

The Jeffsy and the Spectral are inevitably going to be compared. On the face of it, and on the trail, they’re similar bikes.

Both feature tidy carbon frames, with neat finishing touches and great aesthetics.

The Spectral has more radical geometry, largely thanks to a long 500mm reach, compared to the Jeffsy’s 475mm. This contributes to the Spectral’s 850mm front-centre, which is 40mm longer than the Jeffsy’s.

Add in the Canyon’s KIS system, where the springs pull the bar back to centre in order to calm handling over loose terrain, and ‘connect’ the front and rear wheels, and it’s perhaps not a surprise that the Spectral just has the edge in fast, steep and technical trails.

Both bikes have a playful attitude, although I’d suggest the Jeffsy has the edge here – it’s fun and engaging to ride, even with its updates from the previous generation.

I’d argue that, at RRP, the Spectral represents better value, though.

Yes, the 36 Rhythm is a cheaper fork, but I prefer the Spectral’s Shimano SLX brakes, and most of the other items of kit are largely similar.

YT Jeffsy Core 3 bottom line

The YT Jeffsy Core 3 is a great trail bike.

Up hills, it blends grip-giving suppleness with efficiency, ensuring you aren’t spinning out, nor wasting watts.

Downhill, the bike is capable on a broad range of tracks, from fast and flowy to much more chunky.

It’s a fun bike, but this version feels like a more mature version of the previous-generation Jeffsy, being calmer and more composed on choppier terrain, while perhaps losing a little of its poppy streak.