YT Industries Jeffsy MK3 Core 5 first ride review

YT has brought some long-awaited updates to its trail platform. Here's our first ride report

Liam Mercer

Oct 25 2023

YT Industries’ Jeffsy has filled the role of an all-round trail mountain bike since its conception in 2016. The name has become synonymous with trail riding and received high acclaim for its solid blend of capability and versatility. Today, YT has unveiled the third-generation Jeffsy and upgraded it with a host of long-awaited updates to elevate its ride character. We tested it in Forest of Dean to find out if YT Industries has nailed the notoriously difficult third album.

YT Industries Jeffsy MK3 Core 5 - Technical details

The YT Industries Jeffsy has been built with versatility at heart but with a sprinkle of gravity flavour. As such, the bike now gets 150mm of suspension at the front and 145mm at the rear, a respective 10mm and 5mm increase.

Its geometry has also been tweaked. The large frame I sampled, gets a 475mm reach, a 64-degree head tube angle, and a 77.2-degree seat tube angle. There’s a size-specific chainstay that measures in at 437mm on S, M, and L bikes and goes up to 442 on XL and XXL frames. The bottom bracket drop is 33mm, but all of that can be steepened and raised thanks to a flip-chip.

It’s not just a case of nip and tuck with the geometry this time around, as YT has paid special attention to the seat-tube angle. Each size gets its own effective seat-tube angle which steepens as the frame gets larger and this has been done to offer the average saddle height for that particular frame size. So the effective seat tube steepens from 76.9 degrees to 78.6 across the size range but, at YT’s assumed height, the saddle sits at 77.2 degrees. Of course, this depends on your saddle height.

Another change, apart from its uber sleek new look, is a cool downtube storage that’s purposely been put above the bottle cage mounts in order to negate all chances of a wobbly bottle cage. It’s not just a hole cut into the frame either as at each end there are stops built in to prevent excessive rattle. Speaking of which, every bike comes with a bottle and cage right out of the box.

Finally, YT Industries has tweaked Jeffsy’s suspension kinematic, with a 105 percent anti-squat at 30 percent sag that’s said to drop away quickly as it dives past the sag point and that should minimise pedal kickback. The brand says that this also increases acceleration on the pedals and traction basically everywhere. There’s also a bit more end progression compared to the previous model.

YT Industries Jeffsy MK3 Core 5 - Componentry

For my couple of days with the latest Jeffsy, I was treated to the top-spec build which came with the most modern of conveniences, namely SRAM’s XO Eage T-Type AXS drivetrain. Interestingly on this bike, YT has picked the two-button rocker shifter, rather than SRAM’s latest POD offering because the man behind the brand, Markus Flossman, prefers the ergonomics of the older unit. I must say, I agree.

With its fancy drivetrain, the Core 5 build comes with a raft of luxurious componentry, including a Fox 36 fork and Float X damper in the brand’s Factory variety. This level of Fox kit gets the uber-slippery Kashima coating and all the adjustments you could dream of.

This build rolls on a pair of Crankbrothers Synthesis Enduro alloy wheels which has become a mainstay of most of YT’s spec sheets. Each wheel is tuned for the specific use at each end of the bike, so the front rim is wider and there are fewer spokes for more control and compliance, whereas the rear gets more spokes and a narrower rim for a more durable wheel and less rolling resistance. However, YT has chosen to stick with alloy rims, rather than carbon for increased hardiness on technical terrain.

Along with the Renthal finishing kit is an updated version of YT Industries’ Postman dropper that now gets some adjustability as well as clamping bolts mounted to the side of the head, which now features a lower stack.

YT Industries Jeffsy MK3 Core 5 - Performance

The first day of testing consisted of some of the finest trails around the Forest of Dean region, including hand-cut berms and lips littered with natural but easy-going technical features. On the second day, we headed up to Risca for some more intensive testing, as we took the tail end of Hurrican Lee directly to the face.

I’m a big fan of the bike’s new silhouette. Out goes the top tube/seat tube brace and in come tubes with a more flowing form. Not that the last generation Jeffsy looked bad but YT’s mild tweaks make it look far more contemporary.

On paper, the geometry is nothing too far out from the norm. The figures are fairly common on a bike of this type and it didn't take long for me to adjust to things.

When being pushed through transitions and corners, the brand's conservative take on the new geometry design has paid off. It’s been lengthened enough to encourage a very confident level of stability but as soon as it’s leaned into a turn, that reasonably short chainstay and well-positioned bottom bracket keep the fun coming. It’s keen to be whipped around the tightest of corners but without sacrificing traction, unless that's what you're looking to unlock – in which case, it will reward you.

The Jeffsy is easy to ride fast, which came as a huge surprise given some of the conditions it faced. Where traction should have been scarce, the Jeffsy managed to claw something up and when combined with its longer and slacker geometry, unwavering confidence at speed comes incredibly naturally.

What really took me by surprise was the properly sorted suspension kinematic – something most brands consider the holy grail. When pedalling, the shock does not move and, because of that, it’s quick up a hill. Most noticeably, cheeky pedal strokes pay back in dividends, rewarding with easily regained momentum when cranking up surprise mid-descent climbs. In these situations, the Jeffsy felt like a bike with far less travel, offering a level of responsiveness on the pedals that brought me right back to the Canyon Spectral 125, a bike with only 125mm of rear-end squish.

But I say holy grail because it’s a platform that is keen to open up when things get chunky, too. It’s a very well-designed layout that keeps the rear wheel hugging the ground when you want it, almost making it feel more than 145mm of travel with heaps of support under compression. So it can happily be pushed quickly through all manners of tech without being reprimanded but it’s more than happy to pop out of berms and get airborne, too.

YT Industries Jeffsy MK3 Core 5 - Early verdict

This suspension kinematic, plus its wisely selected geometry figures results in a very well-rounded bike. It's a machine that'll happily be pedalled around blue, red and black trail centre tracks while remaining a force to be reckoned with when being pushed down steep and natural terrain. YT has built this bike to handle almost everything.

Having only spent a couple of days on the bike in very mixed conditions, it’s tough to highlight any downsides but I felt as if the dropper post was a little on the short side, something that I’ve found on other YT bikes, too. Even though this large frame gets 170mm of drop, its seat tube is short at 435mm and I noticed other journalists had their droppers somewhat far out of the seat tube, too. As the Postman V2 dropper is now adjustable, it wouldn’t hurt to spec a longer dropper as standard.

Dropper post woes aside, the YT Industries Jeffsy MK3 shows huge promise and, dare I say, may well be the trail bike to beat in 2024. Its combination of confidence and mischief-inducing ride character, along with its excellent suspension platform has resulted in a bike that epitomises the modern trail bike recipe. It's superb.

www.yt-industries.com

Author block

Liam Mercer

Tech Editor here at off.road.cc Liam can also be found photographing bikes as well as revelling in cycling's intricacies. Whether it's gravel, mountain, or e-MTB as long as it's a bike on dirt, he's happy.