YT Jeffsy Core 3 Review

Should I Buy This Bike

If you're searching for a well-rounded longer travel trail bike, we think you'd be hard-pressed to find a better value than the Jeffsy Core 3. YT sells direct to the consumer, and they offer complete bikes with excellent builds at super competitive prices that most mainstream brands can't match. In addition to the fair price, the Jeffsy is a versatile bike with a moderate geometry that performs well in most situations and is easy to get along with. While its geometry may not exactly be “cutting edge”, it hits a comfortable middle ground and doesn't sacrifice agility or low-speed handling for marginal performance gains elsewhere. Still, this 150mm travel 29er is capable of charging hard on the descents with great stability at speed and it doesn't feel overly bulky or unwieldy at lower speeds or in technical terrain. YT's V4L suspension platform successfully blends good small bump compliance with mid-stroke support and great bottom-out resistance. On the climbs, the Jeffsy is comfortable, handles well, and feels relatively efficient. It's a touch heavy and isn't necessarily the fastest bike up the hill, be we found it capable of climbing anything we put in front of it and long days in the saddle. For the price, the build of this bike is fantastic and helps to enhance its all-around performance and quality feel. It's also shockingly quiet, with no creaks or rattles of any kind coming from it no matter how rough the trail. Perhaps one of the best things about the Jeffsy is that you might actually be able to purchase one. YT's inventory comes and goes, but when these bikes come back in stock they are sold on a first-come-first-served basis. They also sell two other builds, so you can match your new Jeffsy to your budget.

The consumer-direct Canyon Spectral 29 CF 7 is a good comparison to the Jeffsy Core 3. The Spectral also rolls on 29-inch wheels and has 150mm of rear-wheel travel, but it comes with a 160mm travel fork and a more progressive (longer and slacker) geometry. The Spectral charges a fair bit harder on the descents and is super stable at speed and confidence-inspiring in aggressive terrain, but it sacrifices a bit in the low speed, technical handling department as a result. If you're an aggressive trail rider who wants to charge hard on the descents, we'd steer you towards the Canyon. If you're seeking a more well-rounded and versatile ride, then the Jeffsy might be more up your alley. The Spectral 29 CF 7 retails for a couple hundred dollars less, but it comes with a lower-end SRAM NX drivetrain and RockShox Select suspension components.

The Specialized Stumpjumper EVO is another interesting comparison. Like the Jeffsy, it rolls on 29-inch wheels and has 150mm of rear-wheel travel. The EVO comes with a 160mm travel fork, and it has a uniquely adjustable geometry so you can really dial it in to your preferences. The Stumpy is much longer and slacker than the Jeffsy and its head angle can easily be adjusted in 1-degree increments between 63.5 and 65.5 degrees. This makes it essentially 3 bikes in one, anything from a versatile trail bike to a full-on downhill shred machine. The Specialized also has SWAT storage in the downtube and the design and details of the bike are very well sorted. If versatility through adjustability is high on your list, the Specialized is definitely the way to go. We tested the Carbon Comp build which cost just slightly more than the Jeffsy Core 3. It comes with a comparable SLX drivetrain and brakes but downgraded suspension in the form of Fox 36 Rhythm fork and DPX2 Performance shock.

Frame Design

The Jeffsy Core 3 has a full carbon frame with 150mm of rear-wheel travel. YT has employed their Virtual Four Link (V4L) suspension design which is a four-bar or Horst-Link system. The main pivot is situated just above the bottom bracket with pivots on the chainstays just in front of the rear axle and a rocker link attached midway up the seat tube. The frame has an almost overbuilt look and feel with a reinforced head tube junction and beefy chain and seat stays. The frame has molded chainstay and downtube protection, full-sleeve internal cable routing, and room within the frame for a Thirstmaster Fidlock water bottle or a small standard bottle and cage using the included mounting hardware.

The Jeffsy has flip-chips in the lower shock mount to adjust the geometry slightly. The flip-chip adjusts the head and seat tube angles by 0.5-degrees and raises/lowers the bottom bracket by 8mm. Our size XL test bike measured with a 66-degree headtube angle and a 77-degree seat tube angle in the low setting. It has a 638mm effective top tube length and a 490mm reach. The chainstays measured 440mm (435mm on sizes S-L) with a 1247mm wheelbase and 344mm bottom bracket height (low setting). The Jeffsy comes in 5 frame sizes, S-XXL. Our size XL weighed 32 lbs and 10 oz set up tubeless and without pedals.

Design Highlights

• Available in carbon fiber (tested) and aluminum frames

• 29-inch wheels

• 150mm of Virtual Four Link (V4L) rear suspension

• Designed around a 150mm travel fork

• Internal cable routing

• Chainsuck plates to protect the frame

• Integrated chainstay, seat stay, and downtube protection

• Adjustable geometry via flip chip

• Complete builds from $2,999 to $5,199

Downhill Performance

The Jeffsy Core 3 is a solid downhill performer that feels comfortable and composed at a variety of speeds and a range of terrain and doesn't require an expert skill level to enjoy. With 150mm of front and rear travel and 29-inch wheels, this bike is stable and fast, yet its somewhat moderate geometry gives it a balanced, well-rounded feel. It isn't necessarily the hardest charging bike out there, but it is user-friendly and we didn't find any situation on the descents that it felt out of place.

When we say the Jeffsy has a moderate geometry, we're comparing it to other new trail bikes with similar travel and intentions. Most bikes in the same travel bracket are now longer in reach and wheelbase, and they have a degree, or more, slacker head tube angle than the Jeffsy's 66-degrees (low setting). For example, the new Canyon Spectral 29 has a 64.5-degree head angle and a wheelbase that's 3mm longer in a size large than our XL Jeffsy. While it may seem a little behind the current longer/slacker trend, we don't think that's necessarily a bad thing. Where some bikes sacrifice low-speed handling and maneuverability, the Jeffsy maintains a bit of agility and doesn't feel unwieldy in tight, technical sections of trail. At the same time, the bike is still long and slack enough to feel stable at speed and confident on steep and rough trails. Sure, some of the longer and slacker bikes might feel more like downhill plow machines, but the Jeffsy's more balanced demeanor gives it versatility that some of those bikes lack. It didn't strike us as the spunkiest or most playful bike around, but it certainly wasn't opposed to a little time in the air or on the back wheel.

YT has employed their V4L suspension platform on the Jeffsy. We found it to feel great over small bumps and high-frequency chop, giving the bike a very damp and muted feel. We felt the mid stroke was nice and supportive, providing a bit of pop and never feeling like it was wallowing. Running just under 30% sag, we were able to get all of the rear travel, but never once bottomed it out. Even while testing on steep skidders with log and ladder drops, it handled big hits with composure and just the right amount of progression to give up all the travel willingly without feeling harsh. Additionally, the Jeffsy is unbelievably quiet, and this bike makes virtually no noise other than the tires on the trail surface. YT really did an excellent job with the chainstay protection and internal cable routing to keep it nearly silent and distraction free.

As with every other YT bike we've tested, you get a great build for the price with the Jeffsy Core 3. YT did a great job spec-ing this bike with quality components that are ready to be ridden hard. First and foremost, the Fox 36 Performance Elite fork provides a burly, confidence-inspiring front end with loads of adjustability and the quality Grip 2 damper. At the back of the bike, the Fox DPX2 Performance Elite shock takes care of the rear suspension duties. The cockpit features a sturdy and responsive E13 Plus 35 handlebar and stem combo and a YT Postman dropper (170mm size XL) to get the saddle low and out of the way. The DT Swiss M 1900 Spline wheels are clad with a matched pair of Maxxis Minion DHR II EXO tires in a 2.4-inch width. The wheels have a nice muted ride quality, and the tires have an aggressive tread with excellent cornering and braking traction. The 4-piston SRAM G2 R brakes with 200mm rotors front and rear work okay, but feel perhaps a touch underpowered for this bike.

Climbing Performance

The Jeffsy Core 3 performs just fine on the climbs. The geometry is well sorted and the suspension design provides a supportive and relatively efficient pedaling platform. We wouldn't call it the zippiest climber, but for those who aren't concerned with breaking records up the hill, the Jeffsy is a comfortable and capable companion.

At 32 lbs and 10 oz, the XL Jeffsy we tested isn't exactly lightweight. That weight combined with the aggressive tread of the Maxxis Minion DHR II tires contributed to it feeling a bit draggy at times, especially on longer paved or fire road climbs. On the trail, the Jeffsy has a more natural feel, still not an uphill rocket ship mind you, but the comfortable geometry, responsive handling, and moderate geometry feel good in most scenarios. The steep seat tube angle lines the rider up right above the cranks for efficient power transfer and an up-top position that is great for tackling technical sections. The cockpit is roomy without feeling too stretched out, and the wheelbase isn't so long that it becomes difficult to handle at lower speeds or through technical uphill puzzles. The 66.5/66-degree (high/low) head tube angle keeps the handling crisp and responsive. Flip chips in the lower shock mount also allow you to adjust the geometry slightly, and we found the high setting's higher bottom bracket to be preferred for super rocky trails to help avoid pedal strikes.

YT's V4L suspension design provides a nice calm feeling pedaling platform with good small bump compliance and excellent traction in the rear shock's open position. When seated, there's a tiny amount of suspension bob, but not so much as to feel like your precious energy is being wasted. Out of the saddle, the suspension movement is a bit more noticeable but isn't terrible, and we left the shock open on trail and only reserved the compression damping switch for longer paved or fire road grinds.

On the climbs, the build of the Jeffsy Core 3 mostly helps to enhance its performance. The SRAM GX 12-speed drivetrain simply works well with a massive range provided by the 32 tooth chainring and the newer 10-52 tooth cassette. The YT branded SDG Bel Air 3.0 saddle was surprisingly comfortable and proved to be a great place to sit and spin away the miles and vertical while testing. Maxxis Minion DHR II tires front and rear aren't necessarily the fastest rolling, but they do provide loads of climbing traction, even in loose conditions. We weren't too impressed by the freehub engagement of the DT Swiss rear hub. Sure, it works fine, but it does have a somewhat clunky and unrefined feel to it compared to faster-engaging hubs.

Photo Tour

Value

The Jeffsy Core 3 is an excellent value. The price of this bike increased just slightly while we had it for testing, but it's still more affordable than most other carbon-framed bikes with a similar build. YT's consumer-direct sales model helps to keep the price low, and this full carbon bike is shred-ready straight out of the box. There's definitely nothing that needs to be upgraded to get out and tear up the trails on this well-spec'd and affordable ride.

Conclusion

The YT Jeffsy Core 3 is a longer travel trail bike that combines a competitive price, a great build, and a well-rounded performance. This 150mm travel 29er's moderate geometry is comfortable and helps to enhance its versatility and user-friendliness. We found the Jeffsy to be easy to get along with and it performed well on the climbs and was composed and capable on the descents with an impressive terrain bandwidth.

Other Versions

YT makes three reasonably priced versions of the Jeffsy including the Core 3 build we tested.

The Core 2 is the least expensive option and an outstanding value at $2,999. It comes with an aluminum frame and a truly impressive parts spec for the price that includes Fox Performance suspension, a SRAM NX Eagle drivetrain, DT Swiss M 1900 Spline wheels, and Maxxis Minion DHR II tires.