YT is a German direct-sale brand with a strong presence in the more extreme end of mountain biking, so it’s no surprise that its 150mm Jeffsy trail bike is a dab hand when it comes to going flat-out on descents.
I tested the 29er Jeffsy, but 650b options are available too.
The Jeffsy won our Trail Bike of the Year test in 2018, and was updated with a new shape and suspension kinematic just before the 2019 test where it podiumed again. Subtle changes have been made for 2020, and we reckon they make the Jeffsy even better than last year’s bike.
YT Jeffsy Pro 29 frame and suspension details
YT has built the Pro 29 with its full carbon frame, and the 140mm of rear suspension is controlled by a four-bar suspension system.
The frame itself has incredibly clean lines, both for aesthetics and functionality. All the bolts, bar the driveside chainstay pivot bolt, are accessed via the non-driveside to make maintenance easier when the bike is up on a workstand. This also leaves the driveside a lot cleaner looking, certainly around the rocker-linkage.
YT has also minimised ‘shelving’ in the rear triangle, which is an area where mud can collect – so reducing this is no bad thing.
The frame has internal cable routing, with the cables clamped at their exits to reduce rattle, and down tube and chainstay protection are added. The dropped top tube gives ample standover.
YT Jeffsy Pro 29 geometry
YT is bang up to date with the Jeffsy’s shape. It’s not so extreme as to need a complete readjustment to your riding style, but with a long-ish front end, slack head and steep seat angles, there’s little in the way of excuses when you head up or down.
The 435mm seat tube is also especially short, which is great if you want even more length from a bike and are able to ‘size up’.
There’s a flip-chip in the suspension linkage, allowing you to add or drop half a degree and a few millimetres of height – for the purpose of the geometry list, the bike has been set up here in its low setting.
- Seat angle: 77 degrees
- Head angle: 66 degrees
- Chainstay: 43.5cm / 17.13in
- Seat tube length: 43.5cm / 17.13in
- Top tube (effective): 61.5cm / 24.21in
- Head tube length: 11cm / 4.33in
- Bottom bracket drop: 3.2cm / 1.26in
- Wheelbase: 1,226mm / 48.27in
- Stack: 62.7cm / 24.69in
- Reach: 47cm / 18.5in
YT Jeffsy Pro 29 specifications
The Jeffsy’s spec is fairly top-drawer for the money, especially considering the carbon frame. It’s also a spec list that clearly shows that YT has descending at the heart of its DNA.
Suspension comes from RockShox, with a 150mm Pike Select+ fork that contains the Charger damper, while a Super Deluxe Select+ shock controls the back end.
This shock has a piggyback oil reservoir that helps keep the shock cool on long descents, thus keeping its damping more consistent.
E13 wheels are shod in MaxxGrip Maxxis tyres which have a sticky compound for extra grip.
The hubs have RockShox’ over-sized TorqueCaps around the axle, said to improve the hub/fork interface when it comes to stiffness. Whether there’s a noticeable difference on the trail is negotiable, however the caps aren’t the snuggest fit on the hubs, and so were easily knocked while trying to get the wheel in and out, which was a pain.
The rest of the kit comes from household brands such as SDG, E13 and ODI.
YT Jeffsy Pro 29 ride impressions
Our 2020 Bike of the Year testing predominantly took place in the South West of the UK during winter. This included loops round trail centres, natural muddy and rooty tracks dug in to Welsh hillsides, as well as laps at BikePark Wales.
A number of bikes, including the Jeffsy, were taken to Spain for the final set of tests, where we rode on dry, rocky flow trails, super-technical rock gardens and some loamy enduro tracks. Thanks to BlackTown Trails for their help with finding these test tracks.
The Jeffsy was very quick and easy to set up, with RockShox’ suspension being some of the easiest out there to plug and play.
YT Jeffsy Pro 29 climbing performance
YT redesigned the Jeffsy’s kinematics in order to boost anti-squat around the sag point for better climbing performance than the previous generation Jeffsy.
It’s not wallowy, as such, but much more than gentle spinning up hills does get the shock bobbing around a little.
Flick the compression switch on the shock and all is well again, but on rough climbs, you’ll want the shock open to keep the wheels rolling smoothly over undulations.
Quicker rolling tyres would certainly help on climbs. The MaxxGrip compounds add noticeable drag and thus kill an element of zippyness from the Jeffsy on short uphill sprints.
That said, on steep technical climbs, the steep seat angle puts you in an excellent position over the cranks.
Also, the rangy geometry means there’s ample space to move around over the bike, ensuring the front wheel goes where you want it to and the rear wheel grips; if traction is limited, the rear Minion DHRII is as likely to grip as any other tyre around.
YT Jeffsy Pro 29 descending performance
When trails got really chunky, it was the Jeffsy that stood out from the crowd.
Despite being YT’s ‘trail’ bike, the Jeffsy feels like a mini-enduro bike at times, with a do-or-die attitude to big rocks, matted roots or flat-out gap jumps.
YT has switched to Maxxis rubber for 2020, away from the love them or hate them e*13 TRS tyres on the 2019 bike.
There’s a pair of Minion DHRII’s, with the MaxxGrip compound up front, and MaxxxTrail out back, and a well-supported 2.4in carcass that sits on E13 TRS Plus rims with a 27mm internal width.
While grip levels are just as good, the Jeffsy rolls faster and feels more predictable than last year’s contender when you lean it onto the shoulder treads.
The stability afforded by the compound means that even when you bury the wheels into a catch berm, the tyres resist contorting unpredictably, helping you maintain control.
A 150mm Pike Select+ fork is plugged into the 66-degree (Low setting) head tube, giving plenty of bump-eating damping and travel, and a stiff enough chassis to allow you to push it through corners and batter over rocks.
While the Ultimate level forks get independent high- and low-speed compression adjustment, the standard Charger damper in the Select+ feels pretty sweet from the get-go and I didn’t miss the extra adjustability of the Ultimate fork found on the Propain Hugene.
The fork is matched by a piggy-backed Super Deluxe Select+ shock that performs well, giving smooth, controlled and amply adjustable travel that’s easy to set up and can be tweaked with volume spacers quickly, should you wish.
It remained perfectly consistent on longer, pummelling descents, with little in the way of damping changes through heat.
The suspension is supple early on, allowing the rear Minion to scrub speed easily via the SRAM G2 RSC brakes, as well as keeping the chassis feeling calm and composed.
Up the impacts and YT’s expertise when it comes to DH and enduro bikes clearly shows. The shock’s bottom-out bump-stops are barely tickled at full travel as the kinematic’s progression effortlessly slows the shock’s shaft speed down, preventing your ankles from compensating for any harshness.
Its suspension gives it an un-flappable feel, dealing with rocky and rooty chunder, but perhaps lacking the element of pop that some of the more playful bikes have.
On flatter, more mellow trails the Jeffsy doesn’t quite have the same sprightly feeling of some of the peppier trail bikes around, largely thanks to the super-grippy tyres, so riders who spend a lot of time on flowy, woody trails or hammering trail centres might find a better ride on a ‘smaller’ trail bike.
YT has got the Jeffsy’s shape just right: the 470mm reach (Large) and 435mm chainstays give a wheelbase of 1,226mm that’s long enough, taking the head angle into account, to give stability without becoming unwieldy.
This long, yet neutral shape makes it an easy bike to jump on and ride, without the need to reassess how you position your body over your bike.
On the steepest of tracks, the longer front-end provides security to weight the front wheel for maximum control, while still avoiding feeling like it’s going to tip you over the front.
YT Jeffsy Pro 29 bottom line
The Jeffsy is a beautifully built, well-specced trail bike with a definite bias towards the rowdier end of the trail riding scale.
YT has got the shape perfect for such a bike, with an easy to jump on feel that won’t surprise but will flatter and help improve your riding skills.
The rear suspension is excellent, assuming you favour all-out descending performance over some climbing capability. It’s smooth, composed and utterly controlled in virtually every situation.
That’s not to say that it can’t climb, but the small amount of pedal bob and the grippy tyres certainly put the brakes on a little.
All this combines to make the Jeffsy our pick of this year’s Trail Bike of the Year test if you’re looking for a bike that’s sole purpose is getting you down a hill, flat out.