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YT Jeffsy AL Comp 27 2018 Review

A sharp handling aggressive trail bike with a preference for fast flow trails
YT Jeffsy AL Comp 27 2018
Credit: Jenna Ammerman
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Price:  $2,799 List
Pros:  Very fun on flow trails, sharp handling, excellent build kit as a whole
Cons:  Poor shock specification, Very progressive suspnsion design is harsh in sustained rock gardens.
Manufacturer:   YT Industries
By Pat Donahue, Joshua Hutchens  ⋅  Feb 8, 2018
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  • Fun Factor - 25% 7.0
  • Downhill Performance - 35% 7.0
  • Climbing Performance - 35% 6.0
  • Ease of Maintenance - 5% 4.0

Our Verdict

The YT Jeffsy 27 AL Comp is a capable bike that provides high-end performance on flow trails but provides a decisively rough ride on bony terrain. Two testers spent three weeks putting this 150mm travel trail bike through its paces. The Jeffsy 27 offers a rock-solid ride that is at its best on fast and smoother trails. With a healthy amount of rider input, this bike is responsive and playful. Sustained rock gardens are less pleasant. A questionable shock specification and a very progressive suspension design create a rough ride that can dish out a beating to the rider. Climbing skills leave something to be desired. While the climbing motion is calm and smooth, this bike's shock creates an ineffective climbing position in both the open and climb settings. Under rider weight, this bike settles deep into its shock stroke, dropping the rear end too far. This creates an ultra-slack effective head tube and seat tube angles and is detrimental to climbing abilities. At $2,799 the 27 AL Comp is a tremendous value and offers a fantastic build kit.

Our Analysis and Test Results

The YT Jeffsy 27 has received a total overhaul. As a result, the version we tested is no longer available.

Should I Buy This Bike?

Riders seeking an aggressive trail bike that boasts impressive components at an extremely competitive price will love the Jeffsy 27 AL Comp. Yes, there are 140-150mm trail bikes that offer superior performance on rough or old-school trails. That said, few if any can match the quality of the build kit. Riders who prefer new-school flow trails to rough and burly ones will be happy with this bike. If you are considering this aggressive bike to dabble in some park riding or enduro racing, there are better options. Still, the value is high and, at the end of the day, cash is king.

We tested the Jeffsy 29 AL Comp this summer. The 29er version offers 140mm travel while the 27.5 iteration has 150mm of squish. Overall, we prefer the Jeffsy 27. The 29er is our choice for longer rides and wide open trails. The Jeffsy 27 is our choice for the more playful rider who values cornering abilities and flickability. The 27.5 version feels substantially more aggressive and confident at speed. Not surprisingly, both bikes feature that same super-progressive suspension design that makes rough trails jarring.

Riders looking for a more aggressive 27.5 trail bike with better climbing skills should consider the Rocky Mountain Altitude. The Altitude has 150mm of travel and offers more climbing efficiency. This bike hustles uphill like a bike with significantly less suspension. When aimed downhill, this bike is capable and can handle the majority of trails. Enduro-grade steep gnar can disturb the Altitude and push it outside of its comfort level. Our Alloy 50 test bike boasted an impressive value and sold for $3,399 with Fox Suspension and Shimano XT 1x11 drivetrain.

The Canyon Spectral offers impressive performance at an unrivaled value. This bike retails for $2399 and features impressive components such as a SRAM GX Eagle drivetrain, RockShox Pike fork, and aggressive tires. The Spectral offers relatively aggressive downhill performance and sharp handling. Climbing is predictable and efficient.

Not convinced you need quite as much travel? Love the idea of a sporty trail bike? The Commencal Meta TR V4.2 is a 130mm trail bike with semi-aggressive performance. The Meta TR is a reliable climber with solid uphill handling. Despite the chunky weight of our test bike, this bike is easy to power uphill. Downhill performance is precise and handling is sharp. Slicing and dicing your way down your favorite trail is a blast. At $3,249, the Meta TR Essential is yet another impressive value in the consumer direct arena.

YT Jeffsy AL Comp 27 2018 trail mountain bike - virtual 4-link (v4l) is a variation of the horst link design.
Virtual 4-Link (V4L) is a variation of the Horst Link design.
Credit: Jenna Ammerman

Frame Design

The YT Jeffsy 27 is designed around 150mm of rear wheel travel. This is 10mm more squish than the 140mm Jeffsy 29 we tested last summer. The suspension design is dubbed Virtual 4-Link, which is a variation of the popular Horst Link system. YT designed the Jeffsy to be very progressive. This design works well enough, but it is a little too progressive for our liking on sustained rock gardens. Part of the problem for the AL Comp build can be blamed on the questionable shock specification.

Our large test bike has a 622mm effective top tube and 434mm chainstays to produce a 1201mm wheelbase. We measured the reach to be 460mm. This bike features adjustable geometry labeled high and low. This is a straightforward flip-chip system. We rode this bike in both geometry settings with no obvious preference.

In the low setting, we measured our Jeffsy 27 to have a 65.9-degree head tube angle, 74.8-degree head tube angle, and 340mm bottom bracket height.

In the high setting, we measured the bike to have a 66.5-degree head tube angle, 75.1-degree head tube angle, and 345mm bottom bracket height.

Our large test bike weighs 30 lbs 6 ounces without pedals and set up tubeless.

YT Jeffsy AL Comp 27 2018 trail mountain bike - high speeds and fast trails are a blast aboard the jeffsy.
High speeds and fast trails are a blast aboard the Jeffsy.
Credit: Jenna Ammerman

Design Highlights

  • - Available in aluminum and carbon fiber
  • - 150mm of rear wheel travel, designed around 140mm fork
  • - 29-inch version available with 140mm rear wheel travel
  • - 27.5-inch wheels only
  • - Boost Spacing
  • - Two aluminum build kits retailing for $2,299 and $,2799.
  • - Three carbon fiber builds ranging from $3,499 to $4,999.
  • - Available in Small-XL

YT Jeffsy AL Comp 27 2018 trail mountain bike - the jeffsy feels great on an isolated big impact.
The Jeffsy feels great on an isolated big impact.
Credit: Jenna Ammerman

Downhill Performance

Shredding new-school trails is very fun aboard the Jeffsy. With a bit of body language and a dose of speed, this is a responsive and playful bike. Charging down rough sections of trail is less pleasant. The very progressive design provides a jarring downhill experience that can beat you up. The components on our test bike worked well, but we think the rear shock and Maxxis High Roller II front tire could be easily improved.

In both geometry settings, this bike is confident. It isn't phased or deterred by high speeds. The Jeffsy doesn't get the speed shakes or have any obvious geometry flaws on flow trails. It takes a little bit of body language, but the Jeffsy is responsive and works through corners effectively. Dip the shoulder and this bike rails through corners. Riders are encouraged to keep the pedals turning on the downhill to keep building speed. This bike is very balanced in the air and has an appetite for side-hits and boosts.

YT Jeffsy AL Comp 27 2018 trail mountain bike - the jeffsy 27 is happy to hop around the trail.
The Jeffsy 27 is happy to hop around the trail.
Credit: Jenna Ammerman

Riding rough and bony trails is less awesome. Much like the Jeffsy 29 we tested, the super progressive feel detracts from performance. It should be noted that since the Jeffsy stays higher in its travel and doesn't compress as much as more plush and linear bikes, it might be faster. That said, it can be too physically demanding and uncomfortable for riders who aren't racing the clock. When you are motoring through rocks, it feels like your riding a bike with far less travel. This can be downright jarring and harsh. This bike really demands proper form and soft elbows/knees through rock gardens to take the edge off. Larger, isolated, hits are absorbed effectively and you are going to have a hard time bottoming out on this bike.

We ran up to 40% sag on our RockShox Deluxe RT and still couldn't get through the travel. There were no volume bands in our shock. We feel a higher end shock where you can tune high and low-speed compression could go a long way in helping this bike feel a bit more plush. A coil shock, which is inherently more linear than an air shock, could be a nice choice too.

The Maxxis High Roller II tires performed well enough in testing. That said, a more aggressive front tire would go a long way. A Maxxis Minion DHF would inspire a bit more confidence leaning into corners.

YT Jeffsy AL Comp 27 2018 trail mountain bike - the effective head tube angle, when sagged into its travel, makes...
The effective head tube angle, when sagged into its travel, makes for tricky climbing position.
Credit: Jenna Ammerman

Climbing Performance

The Jeffsy 27 is a solid climber that is limited by some components. The calm and relatively bob-free climbing motion is hampered by how deep this bike settles into its shock stroke in climb mode. Seated or standing the way the shock settles deep in its stroke to creates a very slack effective head tube and seat tube angle.

This bike has an impressive climbing motion. If we briefly ignore our problem with the rear shock, the Jeffsy is a calm and effective climber. There is minimal pedal bob, and grinding uphill is impressive for a 150mm travel bike.

Our main issue climbing this bike is how the bike gets stuck deep in its shock stroke. Even with the use of the climb switch, the Jeffsy sinks down into its wide open sag point and creates a very slack effective head tube angle. Most bikes have shocks where the climb switch holds you up higher in the stroke and prevents the geometry from getting too wonky. We measured the effective head tube to slacken to approximately 62.1 degrees when sagging to approximately 35%. One obvious solution would be to run more air in the shock, but downhill performance will become even harsher.

YT Jeffsy AL Comp 27 2018 trail mountain bike
Credit: Jenna Ammerman

Uphill handling is reliable and went relatively undiscussed among testers. This is a good thing. The manageable wheelbase makes it easy to pull this bike up and over obstacles. The front wheel stays planted and navigating tight switchbacks is relatively easy.

The components on our AL Comp build kit worked well on the climb. The E*Thirteen 11-46-tooth cassette is a fantastic addition. The 32:46t climbing gear is manageable. We would still rather see a 30t chainring up front to provide an even more relaxing climbing experience.

Photo Tour


The YT Jeffsy 27 AL Comp is an impressive value. Quality components at an impressive price and solid performance are a recipe for success. There are better performing bikes in the aggressive trail category. That said, potential buyers will be hard-pressed to find a better value at the sub-$3000 price point.

Build Highlights

  • - RockShox Pike RC — 150mm travel
  • - RockShox Deluxe RT rear shock
  • - Shimano SLX 1x11 drivetrain with 32:46t climbing gear
  • - SRAM Guide RS brakes
  • - E*Thirteen TRS+ dropper post
  • - DT Swiss M1900 Wheelset
  • - Maxxis Minion High Roller II 2.4-inch tires front and rear

YT Jeffsy AL Comp 27 2018 trail mountain bike - a well-equipped bike for $2,799 is hard to argue with.
A well-equipped bike for $2,799 is hard to argue with.
Credit: Jenna Ammerman


The Jeffsy AL Comp is an aggressive trail bike with a clear preference for fast and flowy trails. Riders who prefer slashing through berms and carrying speed will like this bike. The super-progressive rear end makes rock gardens feel harsh. The Jeffsy is a respectable climber although it tends to settle too deep in the shock's travel, creating a very slack sagged or effective head tube and seat tube angles. Regardless of its shortcomings, potential buyers will be hard pressed finding better components on a harsh but rock-solid frame that sells for $2,799.

Pat Donahue, Joshua Hutchens

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