As has become standard, the Jeffsy boasts Boost 148 rear axle spacing. Cable routing is mostly external apart from the dropper that enters the seat tube just above the bottom bracket junction, and the rear derailleur cable which runs internally. Fortunately, the other cables run neatly on the top of the down tube with guides doing a good job of keeping them in place and minimising excessive rub.

As with their Capra and Tues, the Jeffsy makes use of a Virtual 4 Link suspension system that has a progressive suspension design with easy movement through the mid travel and support ramping up close to the end of the range. Unlike the Capra, there is no strut between the downtube and seat tube supporting the linkage. The rocker link bolts are also very neatly hidden under the seat stay. This has freed up some space in the front triangle to fit a small, proprietary water bottle and mount. The mounting and bottle can be added to the bike at checkout and did not come with our test bike.




Build Specifications

  • FrameJEFFSY CARBON 29"
  • Bottom bracketRACE FACE TURBINE
  • Rear derailleurSRAM X1
  • ShiftersSRAM X1
  • BrakesSRAM Guide RSC
  • CassetteSRAM XG 1150
  • ChainSRAM PC1130
  • TyresONZA IBEX
  • HeadsetACROS AIX-326
  • Actual weight13.23 kg including YT mudguard and Shimano SPD pedals

Specification Highs & Lows


The wheels are the only have-to upgrade on my list of "Lows". With an inner diameter of 22.5mm (outer diameter: 27mm) the DT Swiss M1700 Spline wheelset is the weakest link on the specification sheet. I swapped these out for a cSixx XCM 29 wheelset which has an inner diameter of 26mm which made a significant difference in terms of the tyre profile, and therefore grip and traction, and stiffness. Wheel deflection was also notably better on the wider carbon cSixx rims.

The saddle has proven itself incompatible with my body. I'm not one to shy away from a low profile saddle but, even though I have owned one before, the SDG Circuit was not my idea of a day's fun in the sun. It was simply too narrow and hard and became uncomfortable on longer rides. I first tried Specialized's Power saddle and then their Henge Comp - both of which were comfortable, with the Henge staying on the longest. I have since put one on my Knolly Warden as well.

The Rockshox Reverb lever sits in an awkward place. I prefer it to be on the left-hand side below the handlebar, as it is quite a bit easier to push and actuate the dropper without too much movement in your hand. Swapping this out will only follow a wheel upgrade and while I'm at it, I will most likely change it out for RockShox's 1x remote lever.

The Race Face Love Handle grips are quite thin and I found them tiring on longer rides. These made way for a set of ODI Rogue grips I had in my spare stash. These were then replaced by SDG Hansolo Lock-On Grips which are also manufactured by ODI. I found these to be a perfect match for all-day rides as well as the shorter, more technical blasts that the Jeffsy is capable of.


With the wheels the only exception, the bike arrives kitted out ready to ride. Great tyres, nice wide bar with a short stem, solid suspension in the Pike fork and Monarch shock, and a dropper seatpost as standard. Simply put, the bike comes very well specced straight out of the box, and even more so considering the asking price and capability.

On the Trail

At 179cm with an 84cm inseam (77cm saddle height) the large size with its 445mm reach was a perfect fit with the stock cockpit. Size-specific rears are a nice touch with the L and XL running chainstays being 5mm longer than the S and M.

The YT Jeffsy does a remarkable job of being capable and well-balanced in both the high and low geometry settings. You won't hate climbing and just riding along in the low setting and you won't loath descents and technical sections in the high setting. Some bikes, when dropped to the low setting and fully geared towards descending, are a real battle with climbing and/ or pedal strikes. Conversely, some bikes in the high setting actually feel too upright, which leads to a drop in confidence when railing corners. Although the differences, and certainly the benefits of each setting can be felt, the bike is competent in either setting.

It is a capable climber and makes light work of climbs even with the all-mountain Onza Ibex tyres. I settled on a shock setup that leaned towards plush, running 25% to 30% sag. This had me using platform damping on my way to the top on longer rides.





Through rough stuff the rear is nicely isolated from braking, keeping the suspension active when needed. Stay off the brakes for as long as you dare and the bike rewards with good old fashion fun. Overall traction and grip are excellent with the tyres and suspension doing a great job of keeping up with the dialled geometry and balanced feel. As mentioned above, I swapped the wheels out for a carbon wheelset that was both wider and lighter. This elevated the ride even further and is certainly something I would recommend to those looking to eke every last drop of fun out of the bike

Simply put, the YT Jeffsy 29 is an incredibly fun and capable bike. So much so that between the mountain bikes I have at my disposal (Knolly Warden Carbon, Momsen VIPA Trail, and Momsen ST-F29) it was the bike I rode the most this year. Compared to other bikes reviewed this year, the Jeffsy was the one I always liked to come back home to and quickly became my benchmark bike.

It transcends categories as it will happily be your play pal and do duty on race day should you choose to. If you participate in stage races often enough you can add a lighter wheel & tyre combo to the mix and still cash in on the fun bits. Thanks to the 29er wheel size and balanced suspension it will cover distance with ease, with the only real drawback being its weight on very long rides involving serious climbing. But I'm saying this as a comment to the marathon crowd in comparison to a race focused steed, so not really natural territory for the Jeffsy.

The reason for highlighting that is to try and convey just how capable this bike is, and just how suited it will be for a large portion of riders out there. If you're a trail rider at heart who does the odd race or two, this could be the bike for you. If however you are a racer who rides trails as part of your training only, then maybe look at one of the excellent 120mm 29ers out there.

As mentioned in my 3-month update, the only reliability niggle I've had was with the SRAM Guide RSC brakes that suffered a technical issue. Since they have been warrantied they have been faultless and performed as expected. The rest of the bike has been as reliable as man's best friend.





When he reviewed the YT Jeffsy, Nick Webb concluded: "In my reviews, I try to not get too carried away with emotions but with it being Valentine’s Day, I’m allowed to make an exception. I really love Jeffsy! The bike strikes a remarkable balance between an all-day kilometre eater, and big mountain shredder. No matter where you point the Jeffsy, it manages to excite. The Jeffsy has gone straight to the top of my “if you could have only one bike” list."

That is about as spot on as it can be for how I feel about this bike. It is fun, it is capable, it is fast (up, down and around) and it is a looker. Thanks to YT Industries direct to consumer model, it also offers great specification for the money and if you're happy to spend a bit extra to get it exactly how you want it, you could have yourself the perfect all round bike.

If I could have only one bike, one bike to do it all with, it would be this one. Or an Evil The Following.