The updates hint at a bike that’s even happier on the descents than the previous version, which won our Trail Bike of the Year test in 2018. Both 29in and 27.5in versions of the Jeffsy are available, although it’s the 29er that will probably be more popular with trail riders.
The YT Jeffsy 29 CF Pro is one of our Bike of the Year bikes for 2019. To read reviews of the other contenders and the categories tested across road, mountain and women’s bikes, visit our Bike of the Year hub page.
Frame construction seemed top-notch during testing. The linkage bolts are all accessible from the non-driveside of the bike, which makes servicing easier.
The internal routing is neatly designed and YT says it’s reduced the places mud can collect through the rear of the bike.
All the pivot bolts are accessed on the non-drivesideDan Milner
The head and seat tubes are both relatively short, which should help riders who want to ‘size up’ to fit on a bigger bike.
The geometry updates boost the YT Jeffsy’s descending capabilities and contribute a fair amount to the difference in feel of this new generation bike. But, I’d argue it’s the updated suspension kinematic that makes the Jeffsy such a great all-rounder.
RockShox’ Charger damper is one of the best out thereDan Milner
YT has added about 30 percent extra anti-squat at the sag point, meaning the bike is less prone to energy-sapping pedal bob.
Through the pedals, the Jeffsy feels sprightly and eager to accelerate, while there’s still buckets of support to help push against the pedals for generating speed through flowy trails and berms.
YT Jeffsy 29 CF Pro ride impressions
SRAM’s Guide brake family is by far the most commonly seen on trail bikes this yearDan Milner
While the 2018 Jeffsy was ridiculously agile and a heap of fun to ride, thanks to that longer geometry, this year’s model has a more planted feel.
Arguably, this additional capability means the Jeffsy loses some of its fun-loving character, however the added composure through larger impacts and a stiffer chassis mean the Jeffsy is a better proposition when you want to let go of the brakes and plough through terrain.
When it comes to climbs, the updated suspension makes its presence felt. The lack of bob means those higher intensity efforts are more efficient, and the back-end is rock solid when you’re sat pedalling.
The suspension isn’t so tight that there’s no small bump sensitivity, so traction on technical climbs is fine, and there’s little lurch as you crest more square-edged lumps.
YT Jeffsy 29 CF Pro wheelset
There’s a big caveat though, and it’s arguably the Jeffsy’s weak point.
The E13 TRS Plus tyres are very Marmite. During testing on steep, loamy Welsh hillsides, their aggressive tread — especially at the shoulder — and soft compound meant plenty of grip.
Smooth lines on the driveside JeffsyDan Milner
Combined with the 470mm reach (L) and 66-degree head angle, this gives the Jeffsy an enviable feeling through corners.
Pitch the bike on its tyre’s edge, weight and point the bars towards the exit, and let off the brakes and you can be confident of exiting at warp speed.
That soft compound and aggressive shoulder didn’t work as well on the hard, rocky trails of Finale Ligure, though, where we completed the Jeffsy’s testing.
The e13 dropper has a light, quick action that I lovedDan Milner
There’s a noticeable transfer from middle to shoulder as you enter a turn, and that soft compound starts to squirm when it’s pushed into the rocks.
This gives a slightly vague feeling to the bike’s cornering when pushing really hard on rocks and hard-pack.
Our test team all wanted to ride the updated bikeDan Milner
If I had the Jeffsy as a longer-term test bike, I’d be tempted to add a tyre such as the Maxxis Minion DHF up front, which has a slightly more rounded profile and feels more predictable on its shoulder.
And it’s a good thing that YT improved the Jeffsy’s climbing characteristics because the TRS+ tyres aren’t the fastest of rollers — the Jeffsy climbs well despite the tyres, rather than the tyres helping to keep things efficient.
YT Jeffsy 29 CF Pro spec overview
The Jeffsy’s updates make it hugely capable on a wide range of trailsDan Milner
The 800mm-wide Race Face Turbine bar mated with a 50mm stem allow you to muscle the bike around, while the 200mm rotor at the front aids the SRAM Guide RS’s overall ability to bring the bike to a controlled stop.
While the 2018 Jeffsy won Trail Bike of the Year thanks to its cheeky attitude, the 2019 version has grown up
SRAM’s GX Eagle groupset is a fine drivetrain on a bike like this, however I reckon a 32t ring, rather than the 34t, would be better suited to the bike — especially given the bigger hoops.
There’s a 600ml bottle made specifically for the Jeffsy — available for all frame sizesDan Milner
YT has fitted a 600ml bottle into every size of the Jeffsy frameset, but you’ll need to use the YT bottle with the Fidlock system — and it does rattle a bit.
A final thumbs up goes to the E13 TRS Plus dropper, which has a fantastically light feel and snappy return through the grip-taped lever.
YT Jeffsy 29 CF Pro overall
Tyres aside, the Jeffsy 29 CF Pro is still a benchmark when it comes to all-round performance. The upgraded climbing capability, matched with that new geometry, ensures it’s still hugely capable when the trails return to the valley floor.
The suspension is supple enough to deal with small bumps, yet progressive when things get chunky.
While the 2018 Jeffsy won Trail Bike of the Year thanks to its cheeky attitude, the 2019 version has grown up — simply put, it’s a better bike technically.
It might have lost some of its cheekiness, but it’s still a great all-round trail bike that I’d gladly recommend.
Riding since the age of 13, Technical Editor Tom has ridden hundreds of bikes over the past few years, from aero race bikes to EWS-ready enduro rigs, with a fair few others in between. Most likely found in the woods practicing his scandi-flicks.