The Jeffsy has a solidly-built frame, the main pivot is very wide, and the rear stays and pivot junctions are properly chunky. A flip chip lets you change the frame angles by half a degree.
There’s reasonable clearance around the 2.4in rubber fitted, but no chain guide mounts and only space for YT’s own stubby, side-loading Thirstmaster 3000 cage and bottle (£41.90!).
The 29er version has a shorter reach than the 650b-wheeled Jeffsy 27 (445mm on the large) and its tall seat tube makes sizing up a no go.
YT Industries Jeffsy 29 kit
A flip chip lets you change the frame angles by half a degreeMick Kirkman / Immediate Media
Fox’s Rhythm is an awesome fit-and-forget fork for the price and YT has specced a short-offset version (44mm) here for a stability/agility double win.
DT Swiss’s M 1900 wheels offer a great ride feel and killer reliability, and their 30mm width is fully exploited by the 2.4in Maxxis Minion DHR II tyres. The SRAM Guide R brakes get a 200mm front rotor for extra stopping power, and the 780x35mm Race Face bar adds extra steering authority.
While the Shimano SLX mech and shifter have a light and easy action, shifting across the wide-range e*thirteen cassette is clunky and the smallest 9t cog is noisy and rough.
The grip-taped lever of the e*thirteen dropper is a joy to use, but the single intermediate position of the post is hard to engage on the fly and reliability hasn’t been great on our long-term samples.
YT Industries Jeffsy 29 ride impressions
The carbon Jeffsy 29 won our Trail Bike of the Year mega test and the alloy version is a fast, agile and enjoyable bike on all but the toughest trails. While they’re slightly heavier to get going, its 29in wheels still have a rolling advantage over 650b hoops and its 2.4in DHR II tyres grip decisively in the turns.
Thanks to the YT’s relatively short length and fast-reacting fork, it hustles through tighter, slower sections. The fork and shock are tuned relatively tight off the top to give a firm feel that helps it skip and skim over the top of roots and rocks rather than hugging the ground.
The fork and shock are tuned to give a firm feel that helps it skip and skim over the top of roots and rocks rather than hugging the groundMick Kirkman / Immediate Media
It pedals cleanly and efficiently enough to make the ‘medium’ low-speed compression lever setting on the Fox DPS shock largely redundant, and drives and pumps well off backslopes and drops to create extra speed.
With a linear action, the rear suspension does find its speed-carrying limit relatively soon over bigger stuff, though. The firm SDG grips and stiff 35mm bar don’t do anything to isolate impacts either, so you’ll soon start to feel beaten up if you’re pushing the Jeffsy hard.
While the 29in wheels and shorter-offset fork help with stability, the limited reach, wheelbase and 760mm bar can make it feel more twitchy and less settled than other bikes in faster turns and flat-out sections. It also feels cramped for air on longer climbs/efforts.
Despite these major handicaps, the Jeffsy 29 is still a fast and enjoyable bike. That makes the short reach and the excessively high seat-tower arrangement, which stops you sizing up, doubly frustrating. Especially when the 650b version of the bike gets the same big bar and aggro tyres — which show it’s intended to tackle serious trails — along with the progressive dimensions the 29er is lacking, for the same price.