The new YT JEFFSY has caused quite a sensation. However, for this group test, we had last year’s model. The reason for this is that YT currently only offer the new frame in a carbon version which is outside the price limit of this test. Can the bike still deliver?

For an overview of the test fleet head to The best budget trail bike of 2019 – 11 mountain bikes head to head

YT JEFFSY 27 AL Base | 150/150 mm (f/r) | 14.48 kg | € 2,299

Although YT JEFFSY 27 AL Base’s frame has remained unchanged for two years now, the bike is far from outdated. A beautiful shape with a modern design, good componentry, and the whole thing for only € 2,299 – fantastic! The entry-level model we tested comes with FOX suspension consisting of a Rhythm fork and a Performance shock, both offering 150 mm travel. Shifting is taken care of by a SRAM NX-Eagle 12-speed drivetrain, and you’ve got MAXXIS Minion DHR II tires providing grip. We were also impressed with the smooth performance of the 150 mm SDG TELLIS dropper post. The only components we didn’t like are the SRAM Guide T brakes. They simply don’t provide enough braking power for a bike as capable as the JEFFSY. Helping riders leave their backpack at home, YT have developed their own water bottle and cage that fits into the space under the shock – there’s not enough room for a regular bottle. Unlike its 29er aluminium counterpart, the 27.5″ frame has internally routed cables for a cleaner, sleeker look.

Bang Boom Bang – the JEFFSY likes it rough!

Helmet POC Tectal | Glasse Oakley Jawbreaker Polarized | Jersey ION Tee LS 3/4 Scrub Amp | Backpack EVOC STAGE 12 l | Short ION Bikeshorts Scrub Amp

The YT JEFFSY 27 AL Base in detai

Fork FOX 34 FLOAT Rhythm 150 mm
Shock FOX FLOAT DPS Performance 150 mm
Brakes SRAM Guide T 200/180 mm
Drivetrain SRAM NX Eagle
Seatpost SDG TELLIS 150 mm
Stem Race Face Affect 50 mm
Handlebar Race Face Affect R 780 mm
Wheels DT Swiss M1900 SPLINE 27.5″
Tires MAXXIS Minion DHR II 2.4″

Better closed
The FOX 34 Rhythm delivers a solid performance overall. Heavier and active riders should definitely close the low-speed compression by at least one-third to avoid excessive sag.
The SRAM Guide T-Brake can’t live up to the demands of the JEFFSY. It lacks power and reliability. Besides that, adjusting the lever reach is very fiddly.
The climb switch lever easily jumps from open to trail mode. During our tests, the shock switched from closed to open by itself several times.
An option
If you ride a lot of flat and flowing trails, it may be worthwhile putting the flip-chip in the high position.
For a quick spin
If you like leaving your backpack at home for a quick spin on your home-trail, you should include the THIRSTMASTER 3000 in your order – and yes, that’s really what it’s called.
Size S M L XL
Seat tube 410 mm 450 mm 480 mm 520 mm
Top tube 573 mm 602 mm 625 mm 648 mm
Head tube 95 mm 110 mm 125 mm 135 mm
Head angle 66.5°/67.0° 66.5°/67.0° 66.5°/67.0° 66.5°/67.0°
Seat angle 75.0°/75.5° 75.0°/75.5° 75.0°/75.5° 75.0°/75.5°
Chainstays 430 mm 430 mm 430 mm 430 mm
BB Drop 15/9 mm 15/9 mm 15/9 mm 15/9 mm
Wheelbase 1,138 mm 1,169 mm 1,200 mm 1,224 mm
Reach 415 mm 440 mm 460 mm 480 mm
Stack 584 mm 597 mm 611 mm 620 mm

The YT JEFFSY 27 AL Base in test

The riding position on the YT JEFFSY 27 AL Base is comfortable overall. However, we had to push the saddle as far forward as possible to get our weight further to the front for a more comfortable position on steep climbs. You will also want to activate the climb switch to prevent the pedal bob you’ll have to contend with if you don’t. The bike is guaranteed to get you to the top of the trailhead, but there is no mistaking YT’s priorities when they developed this bike.

Tuning tip: more powerful brakes

Typical of the direct-to-consumer brand, it’s all about good times on the descent, and there is a lot of that to be had on this bike despite the low price! It takes a while to get the JEFFSY 27 AL Base up to speed, but once it’s going, it’s hard to stop. The rear suspension is very sensitive with seemingly bottomless travel, the geometry is confidence inspiring and very composed. Demanding, rough trails don’t faze it at all. However, some of the rider’s energy is sapped on easier flow-trails. It might be worthwhile adjusting the flip-chip to the steeper geometry setting for those kinds of trails. The FOX 34 Rhythm performs solidly, though it can’t quite keep up with the better forks in the test field. It feels less defined, especially on fast, repeated hits. Overall, the geometry is nicely balanced, but the plush rear suspension means you have to actively get your weight over the front of the bike to avoid understeer – the YT wants it steep! Still, it corners very predictably and is generous in forgiving mistakes. If you’re thinking of signing up for your next Enduro race, the JEFFSY 27 AL Base is the right partner for you.

Just pull up, the JEFFSY will take care of the landing!


The YT JEFFSY 27 AL Base is a bike for those who like descending hard and fast! It convinced our test crew with its plush suspension, good geometry and decent spec at a very fair price. Although it will get you up to the top of every trail, the JEFFSY has a more relaxed approach to climbing.


  • very composed on rough trails
  • excellent rear suspension
  • good value for money


  • sluggish climber
  • underpowered brakes in steep terrain
  • a bit cumbersome on flat trails

Riding Characteristics



  1. sluggish
  2. efficient


  1. cumbersome
  2. playful


  1. nervous
  2. confident


  1. demanding
  2. balanced


  1. harsh
  2. plush

Fun Factor

  1. planted
  2. poppy

Value for money

  1. terrible
  2. very good

Technical Data


Size: S M L XL
Weight: 14,48 kg
Travel (f/r): 150/150 mm
Wheel Size: 27,5"
Price: € 2,299

Intended Use

XC 8
Trail 9
Enduro 10
Downhill 11

For more info head to:

The test field

For an overview of the test fleet head to The best budget trail bike of 2019 – 11 mountain bikes head to head

All bikes in test: Canyon Spectral CF 7.0 | FOCUS JAM 6.8 NINE | Giant Trance 29 2 | MERIDA ONE FORTY 800 | Propain Tyee AM Performance | RADON SLIDE TRAIL 8.0 | ROSE PIKES PEAK AM1 | SCOTT Genius 950 | Specialized Stumpjumper Comp Alloy 29 | Trek Remedy 8

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