The latest (and greatest?) YT Jeffsy Core 5 is down 5mm on travel from the old bike and now stands at 145mm with a 150mm fork. In a world where bikes are constantly getting longer, lower, slacker, burlier, and more aggressive, this is something of an oddity. There’s no Side Wing either, that asymmetrical strut between the downtube and seat stay, an addition we were expecting to see here. So what exactly is YT up to here?
YT’s done all this to better settle the Jeffsy into its range, 20mm shorter in travel than its big brother the Capra, an enduro bike with 165mm travel in its full 29er build. Admittedly it’s now closer in travel to the downcountry Izzo with 130mm of bounce, but the Jeffsy is intended for burlier trails and more aggressive riding than our favorite short-travel whippet.
Moreover, YT wanted to make Jeffsy excel in the area all trail bikes need to - pedaling performance and climbing ability. Most of us don’t buy a trail bike to sling it on the back of an uplift trailer, instead we need to earn our descents, and that means efficient climbing and decent support from the suspension.
The anti-squat characteristics have been adjusted too, with YT’s suspension engineers getting to work to increase the figure and better hold the bike in the right position. In theory the Capra shouldn’t bob as much on the climbs then, and will stay settled when braking and accelerating.
YT has also added more progression to the shock tune, to stop the bike bottoming out over drops or when you get something wrong. Add all this up and it means there’s less suspension in the first place to play with, and the bottom of the stroke will be harder to dip into. Could we be on for a harsh and bumpy ride then?
Design
The Jeffsy keeps its four-bar linkage design, the shock is driven directly by the seatstays, which is almost certainly lighter and simpler than the Capra’s yoke-driven design. In fact from the side the Jeffsy looks pretty similar to the old bike, the only obvious difference being the now missing bridge between the top tube and seat tube - YT has filled this in and given the bike a chunkier and more modern aesthetic.
Look closer though and you’ll see YT has added internal downtube storage, previously the preserve of top-end brands like Specialized and Santa Cruz. Chopping a hole into the downtube of a bike isn’t the easiest thing to do because the surrounding area needs reinforcing, adding weight and cost. However, in a world where the most exclusive brands add this functionality, and direct sales brands like Canyon look like getting in on the action too, it’s a must.
The Jeffsy’s storage doesn’t have the biggest door, it’s decently wide but not quite long enough and that makes getting things in and out a little fiddly. But inside there are two waterproof tool wraps, and the door itself is watertight, making the whole package a decent proposition.
YT’s bikes haven’t been big on sizing in recent years, but the Jeffsy looks set to change that. At the bike’s launch, I rode the size XL, which had a 495mm reach when we ran a tape measure across the bike. YT has added around 20mm to the bike’s length across the range, meaning it’s introduced a good size order change. In fact, with a low top tube and good standover height you can now choose between two sizes.
Barely anything else has changed in the Jeffsy geometry charts, bar an updated seat tube angle that’s now bespoke to each size. The idea is to give each size in the range an identical effective seat tube angle of 78 degrees across all sizes. The two different chainstay lengths from the Capra have also been employed, with sizes XL and XXL bikes benefitting from 5mm more room than the smaller models.
Specifications
YT has a history of speccing great components, and the tradition continues here with no expense spared. The introduction of T-Type has increased the allure of the bike and certainly the cost, with a £6,000 price tag previously unheard of on the Jeffsy. I also managed to snap the chain the first day out on the Jeffsy, which is almost unheard of and totally at odds with the SRAM Transmission test that performed flawlessly. I can only assume there was a fault, or I somehow got really (really) unlucky.
YT has specced Maxxis Minion and Minion DHRII tires, which cut a good compromise between grip and rolling speed. And best of all, YT has abandoned its cheap dual compound tires for the latest 3C EXO+ casing models that add a little bit of weight but a whole lot of puncture protection. It has twice the tread and sidewall puncture protection, and a 20 percent protection increase from pinch flats, and I was happy to run the pressures pretty low, all without flatting.
Best of all though is the Fox Factory level suspension, Fox has reduced the compression damping on its latest shocks and forks, so rather than just opening them up fully the settings are now very usable.
Performance
YT’s suggestion is to run the bike at 30 percent sag, or 16mm on the shock shaft, a figure that sounded way too soft. Nevertheless I set it just so, and I’m glad I did. The Jeffsy has supple suspension and it sits into the available travel easily, resulting in a cushioned feel more akin to an enduro bike. Don’t get me wrong, you can get to the limits of the travel pretty easily on big-hit enduro tracks, but there’s no harsh bottom out thanks to that extra progression.
Making a bike pedal better than its forefathers almost always results in a worse feel downhill, and while this could possibly be true with the Jeffsy we’d need a lot more testing and time on the bike to figure this out. My point is, the change has been very subtle, and the bike is still a consummate descender.
It does pedal well too though, something which couldn’t be said about the old Jeffsy, which tended to wallow about too deep in its stroke. It could be something as simple as the improved seat angle, putting the rider into a better position for pedaling that’s allowed for this change. But I think there’s more going on because it’s better when you’re stood up and cranking the bike along too, the Jeffsy feels more urgent and direct, easier to work up to speed, and happier to hold it there.
Six thousand pounds is a lot of money for a YT, apart from the Flight Attendant equipped YT Jeffsy Uncaged 6, I don’t think there’s been a Jeffsy yet to match it for price. It is however the most high-tech bike the brand’s ever made, and honestly I believe it’s good value because of that. It’s definitely expensive, but compared to the competition from other brands the Jeffsy Core 5 delivers a lot - where else can you buy a carbon framed bike for less, complete with Transmission drivetrain, Fox Factory suspension, internal frame storage, and partial size-specific chainstays? Whether you need this of course is debatable, but there are plenty of less pricey bikes in the range to check out, stretching down to £2,500 for the Core 1.
YT’s new Jeffsy Core 5 is actually a good value bike then, despite its high-for-direct-sales price of £6,000. I like it not for the downtube storage, which while useful is a shade too small, but for the improved pedalling performance and the great ride feel when descending.
Early verdict
YT’s made subtle tweaks to the Jeffsy to deliver a better all-round trail bike, concentrating on climbing performance and pedalling efficiency. And they couldn’t help themselves building in internal frame storage and adding SRAM’s Transmission drivetrain too
Tech specs: YT Jeffsy 2023 Core 5
- Price: $6,499 / £5,999 / €5,999
- Discipline: Trail/All-Mountain
- Frame: Ultra Modulus Carbon, 145mm travel
- Head angle: 64.1 degrees
- Seat tube angle: 71 degrees (large)
- Reach: 470mm (mid tested)
- Fork: Fox Float 36 Grip 2 Factory, 150mm travel
- Shock: Fox Float X Factory 210x55mm
- Wheels: Crankbrothers Synthesis Enduro Alloy I9 wheels
- Tires: Maxxis Minion DHF/DHRII 3C EXO+ 29x2.5/2.4in
- Drivetrain: SRAM XO Eagle Transmission crankset, cassette and derailleur, SRAM AXS Rocker shifter
- Brakes: SRAM Code RSC 4-piston brakes, SRAM HS2 200mm rotors
- Seat post: YT Postman V2 170mm post
- Saddle: SDG Bel Air 3.0 saddle
- Bar and stem: Renthal Fatbar 35 780mm bar, Renthal Apex 50mm stem
- Sizes: S, M, L, XL (tested), XXL
- Weight: 14.8kg
