The YT JEFFSY enters our 2025 trail bike the comparison test as the reigning champion after claiming both Best in Test and Best Buy in our latest trail bike test – a double victory no bike had achieved before. But with 15 high-end trail bikes in the mix, the competition is tougher than ever this year. Can the JEFFSY defend its title?
15.3 kg in size L | € 5,999 | Manufacturer’s website
The YT JEFFSY is the only bike in this test that has already proven itself in a previous comparison. As the all-rounder in YT’s MTB portfolio, it sits right between the enduro-focused Capra and the downcountry-oriented Izzo.
Despite the top-tier spec, the JEFFSY CORE 5 remains the most affordable bike in this test, retailing at €5,999. With 150/145 mm of front travel and 29” wheels, it stays true to its trail bike roots. However, at 15.3 kg, it’s of the heavier bikes in this test field. How does the JEFFSY hold up against the latest test field, which is packed with freshly updated trail bikes? Read the review to find out.
For an overview of the test field head to our “Best trail bike of 2025” comparison test – 16 of the most exciting trail bikes in our 2025 group test
The YT JEFFSY CORE 5 in detail
The JEFFSY is available in both aluminum and carbon versions. The frame of the top-tier CORE 5 model is made from what the manufacturer calls Ultra Modulus Carbon, which makes it the only bike in the JEFFSY lineup to feature a high-modulus carbon frame. This is intended to reduce weight while maintaining the same level of strength.
A tool mount at the bottom of the top tube comes standard with a Crankbrothers strap, which includes tire levers and a tubeless repair kit. Just add a spare inner-tube and a pump, and your emergency kit is complete – awesome! Items that don’t fit there can be stored in the STASH Box – yes, that’s the actual name. The storage compartment, which includes a couple of STASH Bags, is cleverly integrated into the downtube above the bottle cage. The lid closes securely and doesn’t rattle, though it’s tricky to access with a bottle in the cage. The STASH Box comes standard with all carbon frames.
The cables are routed internally and disappear into the frame just behind the head tube. Instead of being clamped, the cables are held in place by small rubber plugs. However, these tend to come loose, so we recommend securing them with zip ties. Once that’s done, the JEFFSY reveals one of its strongest qualities – an exceptionally quiet ride, with the generous chainstay protector effectively eliminating chain slap.
The spec of the YT JEFFSY CORE 5
Despite its affordable price, the YT JEFFSY CORE 5 features a high-quality spec. The suspension consists of a 150mm FOX 36 Factory fork and matching FOX FLOAT X Factory shock controlling 145 mm of travel at the rear. Although the fork relies on the older GRIP2 damper, it’s still an excellent choice, delivering a tremendous performance on the trail and offering countless adjustment options. The YT Postman V2 dropper post offers 170 mm of travel, which is on the shorter side and somewhat limits freedom of movement – especially considering that the average in this test is 197 mm.
SRAM CODE RSC brakes do stopping duties, and are combined with 200 mm rotors front and rear, ensuring powerful, reliable deceleration – an excellent match for a trail bike like the Jeffsy.
Shifting is taken care of by a 12-speed SRAM Eagle Transmission X0 drivetrain, which relies on a direct-mount rear derailleur and delivers precise, butter-smooth shifting, even under heavy load. The cockpit consists of a Renthal Apex stem and 780mm Renthal Fatbar handlebars, ensuring a sleek race-ready look.
The Crankbrothers Synthesis Enduro Alloy wheelset with Industry Nine I9 hub ensures reliable performance on the trail. The rims are fitted with a MAXXIS Minion DHF tire up front and a Minion DHR at the rear, both in the EXO+ casing and harder MaxxTerra rubber compound. For increased grip and control, we recommend upgrading to the softer MaxxGrip compound at the front. If you spend lots of time on rougher terrain, you might want to consider swapping to a rear tire with the more robust Doubledown casing for added durability.
YT JEFFSY CORE 5 CF
€ 5,999
Specifications
Fork FOX 36 Factory GRIP2 150 mm
Rear Shock FOX FLOAT X Factory 145 mm
Seatpost YT Postman V2 170 mm
Brakes SRAM CODE RSC 200/200 mm
Drivetrain SRAM X0 Eagle AXS Transmission 1x12
Stem Renthal Apex 35 mm
Handlebar Rhental Fatbar 35 780 mm
Wheelset Crankbrothers Synthesis Enduro Alloy 29"
Tires MAXXIS Minion DHF MaxxTerra EXO+/Minion DHR MaxxTerra EXO+ 2.5"/2.4"
Technical Data
Size S M L XL XXL
Weight 15.3 kg
Specific Features
storage compartment
Flip Chip
Tool Mount
Tuning Tip:
– Secure rubber stoppers with cable ties
– Softer MaxxGrip tire in the front
– Longer dropper post
The geometry of the YT JEFFSY CORE 5
The YT JEFFSY is available in five sizes, S to XXL, offering a suitable option for riders between 153 cm and 203 cm tall. Our test bike in size L combines a compact 475 mm reach and 435 mm seat tube, which is on the longer side but doesn’t significantly limit freedom of movement.
Thoughtful details like the integrated storage compartment and practical tool mount make the JEFFSY not only functional but also visually appealing.
A flip chip in the shock mount allows you to adjust the geometry of the bike, steepening both the 77.2° seat angle and 65° head angle by 0.6°. At the same time, you’ll be reducing the bottom bracket drop from 33 mm to 25 mm. YT rely on two chainstay lengths across the range: 437 mm for sizes S to L and 442 mm for XL and XXL, which is meant to ensure consistent handling across all frame sizes.
| Size | S | M | L | XL | – |
|---|---|---|---|---|---|
| Seat Tube | 385 mm | 410 mm | 435 mm | 460 mm | 485 mm |
| Top Tube | 578 mm | 593 mm | 609 mm | 627 mm | 645 mm |
| Head Tube | 100 mm | 108 mm | 116 mm | 124 mm | 132 mm |
| Head Angle | 65° | 65° | 65° | 65° | 65° |
| Seat Angle | 77.2° | 77.2° | 77.2° | 77.2° | 77.2° |
| Chainstay | 437 mm | 437 mm | 437 mm | 442 mm | 442 mm |
| BB Drop | 33 mm | 33 mm | 33 mm | 33 mm | 33 mm |
| Wheelbase | 1191 mm | 1214 mm | 1238 mm | 1266 mm | 1289 mm |
| Reach | 435 mm | 455 mm | 475 mm | 495 mm | 515 mm |
| Stack | 613 mm | 620 mm | 627 mm | 634 mm | 642 mm |
The YT JEFFSY CORE 5 on the trail
Uphill, the YT JEFFSY is a solid climber, holding its own against bikes like the Canyon Spectral and Santa Cruz Hightower. The riding position is comfortably centered, while the rear suspension is efficient enough to embark on long days in the saddle without having to reach for the climb switch.
On descents, the first thing you’ll notice is the outstanding balance – the YT makes you feel at ease from the get go, as if you’ve never ridden anything else. Steering inputs are translated directly and precisely, yet the handling never feels demanding – just as you’d hope for in a great trail bike.
The JEFFSY remains one of the most agile bikes in the entire test field, on par with the Ibis Ripmo and Canyon Spectral, with only the Specialized Stumpjumper feeling even livelier. At the same time, it’s easy to control and strikes a great balance between agility and composure, though it falls slightly behind the burlier bikes in this test when it comes to high-speed composure. That said, it remains an incredibly fun ride, offering controlled handling in all situations.
The suspension is perfectly tuned for a trail bike – not too soft, not too firm, and just right for both flow trails and natural singletracks. It provides excellent support for pumping, plenty of grip, and enough reserves to handle big hits with ease.
Even without securing a title in this test, the YT JEFFSY CORE 5 remains a clear recommendation for anyone looking for an agile, versatile, and durable trail bike.
Even in 2025, the JEFFSY remains a top-tier trail bike with no real weaknesses. It rides similarly to the test-winning Stumpjumper, though not quite as agile, and encourages fast, playful trail sessions. It’s a bike built for speed, fun, and unforgettable rides.
Who should take a closer look at the YT JEFFSY CORE 5?
The YT JEFFSY CORE 5 is a fantastic all-rounder for anyone looking for a true trail bike. It delivers fun on all types of trails, offers plenty of reserves, and feels at home on both flow trails and technical terrain. After securing victory in our latest test, we rode it extensively and intensively without any technical issues or failures – an extremely reliable bike that perfectly balances fun and performance.
Conclusions about the YT JEFFSY CORE 5
The YT JEFFSY CORE 5 holds its own in this year’s test field. It remains an incredibly fun, agile bike with outstanding suspension, excelling on both flow trails and technical sections. Thoughtful frame details make it easy to ride in everyday scenarios, and even if you invest in a few upgrades to refine the spec, the JEFFSY is still the most affordable bike in this test. Even without a title this year, the JEFFSY CORE 5 remains a clear recommendation.
Tops
- Super fun to ride
- Excellent suspension
- Highly agile
- Most affordable bike in the test
Flops
- Spec could be improved
For more info head to yt-industries.com.
The test field
For an overview of the test field head to our “Best trail bike of 2025” comparison test – 16 of the most exciting trail bikes in our 2025 group test
All bikes in test: Atherton S.150 | Canyon Spectral CF LTD | Canyon Spectral:ONfly CF LTD | Ibis Ripmo XT | MERIDA eONE-SIXTY SL | Norco Optic C1 | Orbea Rise LT M-LTD | Pivot Switchblade Team X0 Transmission | RAAW Jibb V2 | Rocky Mountain Instinct C70 | Santa Cruz Bronson CC X0 AXS RSV | Santa Cruz Hightower CC X0 AXS RSV | Specialized S-Works Stumpjumper 15 | Transition Sentinel X0 AXS | Trek Top Fuel 9.8 GX AXS | YT JEFFSY CORE 5 CF
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Words: Simon Kohler Photos: Peter Walker
