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YT Jeffsy AL One 29 2017 Review

Solid handling, reasonable geometry, and 29er rollover keep the bike capable, but the too-progressive rear suspension is harsh in rough terrain
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yt jeffsy al one 29 2017 trail mountain bike review
Credit: Jenna Ammerman
Price:  $2,999 List
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Manufacturer:   YT Industries
  • Fun Factor - 25% 5.0
  • Downhill Performance - 35% 7.0
  • Climbing Performance - 35% 7.0
  • Ease of Maintenance - 5% 4.0

Our Verdict

The YT Jeffsy 29 offers solid climbing performance and reasonable downhill skills. The Jeffsy is a nice option for long days in the saddle where your not hyperfocused on a single ride characteristic. The suspension design is decisively harsh and tends to beat you up on rougher descents. Bigger, rapid-fire hits force a jackhammering ride. This can knock you off line. The 29-inch wheels rolling well and keep your momentum through rock gardens. The big-wheeler corners with grace, but not with 29er defying skill. Direct steering and compact geometry grant sharp steering and comfortable climbing. The stiff 32:42 gearing is another story. Though it can handle black diamond terrain with admirable stoicism, the Jeffsy is way more fun on mellower, flowing trails without a lot of rock. YT has trouble keeping this little black and red beauty in stock. At $2,999 for the nearly flawless AL One 29 build, it's not hard to see why.
Pretty strong climber
Great on long rides
Fun in flow
Rough rear suspension ride over rocks
The Jeffsy performs best on smooth terrain when only dabbling in technical downhills. New-school flow trails, for instance, are excellent aboard this bike. The Jeffsy can handle anything, making it's a solid choice for a new rider who's not sure what type of terrain they want to ride. The Santa Cruz Hightower is a better climber and far superior descender. If you want sharp handling and a little less aggressive ride, consider the killer ninja-like Ibis Ripley LS. Want to crank up the rad-factor? The hard-charging Santa Cruz Hightower LT is far more aggressive.

Our Analysis and Test Results

The YT Jeffsy 29 has seen a ground-up redesign for 2019. The version we tested is no longer available from the manufacturer.

2017 Analysis and Test Results

Five pro bike testers spent ten weeks and countless Sierra Mountain laps to compare four consumer direct mountain bikes. We pitted the trail-focused YT Jeffsy AL One 29 against its Commencal counterpart, the 2017 Meta TR 4.2 Essential and cross-examined them against their enduro brethren, the 2017 YT Capra AL Comp and the 2017 Commencal Meta AM 4.2 Essential. Then we ranked the four consumer direct models against all the trail bikes we've tested in our Trail Bike Review.

Of note, the Jeffsy was only available in Medium when we purchased our bikes. The other three bikes are Large frames. This wasn't ideal, but it worked, with two of our testers straddling the medium/large size divide.

yt jeffsy al one 29 2017 trail mountain bike review - this wagon-wheeled vessel is easily maneuvered and reacts well to...
This wagon-wheeled vessel is easily maneuvered and reacts well to rider input.
Credit: Jenna Ammerman

Fun Factor

One of our testers describes the YT Jeffsy as a "shotgun of a bike." It gets the job done, but it's got a kick to it. A shorter top tube makes maching downhill over rocks more nervous than wide-open joyous.

The most fun part of having a Jeffsy around is never having to say "no" to a ride, any ride. It loves flow and can take successive punches down the biggest rock gardens that the local Sierra ridges can offer up. The catch? You need to bring skills and guts to the latter type of ride. It can make it through only if you're working for it. The ride quality in the rocks has a jackhammering feel that hedges towards type-two fun. The rolling speed, trail smoothing, and momentum holding qualities of 29er wheels work. The Jeffsy suspends you atop them in a comfortable way.

yt jeffsy al one 29 2017 trail mountain bike review - cornering abilities are impressive on this "big wheeler".
Cornering abilities are impressive on this "big wheeler".
Credit: Jenna Ammerman

A polite bike, the YT Jeffsy only rises above perfunctory fun on flows, foothill type trails. Descending through rocks feels more like enduring than enjoying. The same goes for climbing on it's stiff 32:42-tooth gearing. Where the Jeffsy really earns its keep, and your loyalty is on all-day, mountain-topping, sloggathons. Once your legs are up to the stiff gearing challenge, the bike sticks with you the whole way. Getting out and about in the hills for miles and miles is the kind of a good time we can get behind.

The YT Jeffsy doesn't invite playful behavior like the Ibis Ripley LS, a 120mm travel 29er, nor does it charge like the Santa Cruz Hightower. Of course, the frames of these bikes set you back $3,000 and $3,500 respectively. Opportunity costs in the mountain biking game.

The YT Jeffsy is a predictable and reasonably capable bike, earning it an average fun factor. The Santa Cruz Hightower is a similar bike with a more capable and plus attitude, it scored higher. The Ibis Ripley won the category for its zippy and sporty handling.

yt jeffsy al one 29 2017 trail mountain bike review - fast and flowy trails are where the jeffsy feels most at-home.
Fast and flowy trails are where the Jeffsy feels most at-home.
Credit: Jenna Ammerman

Downhill Performance

While the Jeffsy's stiff suspension can stand up to burly descents, it's not a confident ride. The reliable front end of the bike gets little backup from the rear, which rides like it has less travel than it does. We'd have guessed 120 or 130mm. The Commencal Meta TR is a much easier ride. All these issues fall away as fast as your worldly cares on smooth, sinuous singletrack. The trails where occasional rocky or rooty bits won't last long enough to rattle your ride are far more pleasant. Responsive steering makes for a front end reliable enough to keep you on your chosen line. The trail dictates how much you'll enjoy piloting the Jeffsy.

Adding to the bike's startled and disrupted feeling on rocky descents is the Jeffsy's tight cockpit. All the testers agreed that the top tube feels tight for a medium. We measured it at 578mm. The cramped sensation combines with a short wheelbase and steep feeling head tube angle in both flip chip settings (66.2 / 66-degrees H/L) to feel unstable at speed on descents. The steep seat tube angle (76.2 / 75.5-degrees H/L) centers the saddle in an already too tight cockpit when the dropper's down, adding clutter. We all found ourselves way over the back of the bike when headed down steep hills. The short wheelbase put us right over the rear axle. It's a disconcerting backseat kind of ride. At speed, we still wanted more top tube between us and the rocks.

As a result of the cramped quarters and rough ride, this bike has a speed limit in the rocks. The suspension handles intermittent drops linked by smooth sections no problem. What it doesn't like, is successive hits. These are a shock to your system, and the bike gets kicked off line fairly frequently. Luckily, the 29-inch wheels and responsive handling keep it somewhat forgiving. The Santa Cruz Hightower provides a far more confident ride in sustained rock gardens.

yt jeffsy al one 29 2017 trail mountain bike review - hold on tight through the rocks, this bike is shaken when things get...
Hold on tight through the rocks, this bike is shaken when things get rowdy.
Credit: Jenna Ammerman

On smooth trails letting the Jeffsy run wide open is less of a concern and more of a matter of course. The YT Jeffsy is a snappy and responsive ride and doesn't have a bulky feel. Working around switchbacks requires little forethought or effort. This bike doesn't require a lot of body language, but it responds well to it if you want to give 'er. The rear suspension/shock combo doesn't exactly pop you out of berms — it's more of a gunning for it moto feel. The bike is at its best when laying angles to the dirt and sweeping down smooth trails. The cornering knobs on the Onza Ibex 29 x 2.4" tires hooked up well-enough in dry conditions, allowing us to lay the bike right over. They did blow out in a few corners, and we got a few dual wheel drifts, but they were predictable failures. The narrow 22.5mm rims still irk us though. A wider footprint would be better.

A good strategy is to air over shorter sections of chunk. The Jeffsy is a grounded bike but isn't fundamentally opposed to airtime. The short cockpit works to your advantage, as the handlebars are beneath you and easy to wrest into the air. The short reach can make you feel unstable in the landings.

The YT Jeffsy scored well for its disappointing, yet solid, downhill skills. The slightly burlier Yeti SB5.5 and Santa Cruz Hightower LT win the category. The similarly-equipped Santa Cruz Hightower edged out the Jeffsy thanks to its far more plush and supportive ride.

yt jeffsy al one 29 2017 trail mountain bike review - the yt jeffsy comes in third in the trailish downhill time trial...
The YT Jeffsy comes in third in the trailish downhill time trial course, 0.2 seconds ahead of the last place Meta AM on the 2 minute 45 second trail segment.

The Jeffsy finished second to last in our consumer direct downhill timed trials, as shown above. It is a very tight spread, however, with the winning Commencal Meta TR coming in just 1.9 seconds ahead of the Jeffsy. It is interesting however that the 29-inch wheels didn't win the day against the 27.5-inch competition, a consistent trend in previous testing. The test trail features pedally sections connecting rock drops and tech sections, likely favoring the trail bikes.

yt jeffsy al one 29 2017 trail mountain bike review - the jeffsy is a comfortable climber and its 29-inch wheels stay out...
The Jeffsy is a comfortable climber and its 29-inch wheels stay out of holes.
Credit: Jenna Ammerman

Climbing Performance

The geometry of the YT Jeffsy sets you up for climbing success — upright, over the bottom bracket. Forward positioning keeps the front wheel weighted, prevents wandering and promotes responsive steering. The short wheelbase works around corners with ease. The bike gets right on the line you tell it to, ready to lay down some power. You'll need it. The 32:42 gear ratio demands fitness. This setup doesn't make a whole heck of a lot of sense on a trail bike. Constantly cranking makes it challenging to relax and enjoy the climb. It almost makes us miss 2x drivetrains. A 30-tooth chainring up front (a 28 if you like a real slow roll) or an E*Thirteen extended range 11-speed cassette would go a long way here. The climbing gear does give you nice torque for getting up and over obstacles, but we'd rather just shift for it.

Adding to Jeffsy's climbing challenges, our Rockshox Monarch RT shock developed an odd hitch in its giddy-up midway through testing. When locked into climb mode the first bit the shock is supportive, but not fully rigid. Approximately 35% through its stroke, our shock developed a knock or sticky point with every pedal stroke. It is almost as if it's binding up. It's a bizarre "clunky and dumb" sensation according to one tester. Luckily, it fades into the background after a while. Still, the Jeffsy plodded its way to efficient pedaling. As a result, we tried to avoid, the pro-pedal lockout, though it did keep the Jeffsy's angles from slouching.

We normally have great experiences with the RockShox Monarch RT rear shock and are writing this issue is a one-off. We'll keep you updated on the ongoing investigation.

yt jeffsy al one 29 2017 trail mountain bike review - the jeffsy loves fast, downhill straightaways.
The Jeffsy loves fast, downhill straightaways.
Credit: Jenna Ammerman

The suspension is stiff enough that the Jeffsy climbs efficiently regardless of the shock setting. Standing to crank feels solid and the big wheels help in technical sections. The wagon wheels are particularly effective with a head of steam. The suspension doesn't sag excessively when you're hammering out of the saddle, but it feels more damp than snappy. It holds on to traction though, until the Onza Ibex tires break away in wet conditions. If it's dry, you're golden. You can still feel the sticky point, hub engagement isn't stellar, and you've got 29-inches of wheel to punch out of a corner and up to speed, but it all works if you are willing to.

The YT Jeffsy scored in the top half of test bikes for its solid but bland climbing skills. The short-travel Ibis Ripley, Yeti SB4.5, and Santa Cruz Tallboy ran away with this category. The Jeffsy tied with the formidable Santa Cruz Hightower.

yt jeffsy al one 29 2017 trail mountain bike review - rolling in just behind the yt jeffsy on our rock-tastic technical...
Rolling in just behind the YT Jeffsy on our rock-tastic technical time trials, the Meta TR came in ahead of the last place Meta AM by 4.4 seconds on a 2:45 sec:min course on average.

The Jeffsy won our consumer direct climbing time trial, coming in just 0.5 seconds ahead of the Meta TR and beating the Commencal Meta AM by 4.9 seconds. You can see the full results in the chart above. Those 29er wheels are hard to deny, but they don't outrun the comfortably nimble climbing of the Meta TR by much.

Ease of Maintenance

Key factors when considering a bike are price, performance and the quality of the build spec. The ease or difficulty of servicing the bike should not be overlooked. Frame bearings on full suspension bikes require attention and occasional service to keep running smooth. The suspension, drivetrain, dropper post, and brakes need regular maintenance as well. Our serviceability rankings below are explained in the trail bike review

YT bikes use a variation of the Horst Link design. This system is relatively straightforward and the bearings and hardware are easy to work with. The bearings are a little lower quality than the best bikes on the market and the finishing quality isn't top notch. In addition, the aluminum to aluminum clevis joints can get beat up. The Rockshox suspension has a shorter service interval than Fox alternatives, so we rate it lower. SRAM brakes are harder to bleed than Shimano alternatives and require corrosive fluids.

yt jeffsy al one 29 2017 trail mountain bike review
Credit: Jenna Ammerman

Frame Design and Suspension Overview

A 140mm 29er with a 66-degree head tube angle, the Jeffsy has the bones of an aggressive trail bike. These numbers also belong to the trail-crushing Yeti SB5.5. The Jeffsy doesn't reach that level of performance. YT's extremely progressive Virtual 4-Link (V4L) suspension, based on the Horst Link design, amplified trail chatter, shaking rider confidence. The upside is that the RockShox shock will indeed feel bottomless, and utilize most of its stroke. One of our testers preferred the unalterably stiff feel on both the Jeffsy and the YT Capra. The rest failed to get used to the jarring feel. Another tester described it as unresponsive, EMT speak for dead. The V4L gained efficiency from a rear shock's climb switch when ascending, though the bike doesn't struggle too mightily to make progress in open mode.

yt jeffsy al one 29 2017 trail mountain bike review - a look at the virtual 4-link suspension design.
A look at the Virtual 4-Link suspension design.
Credit: Jenna Ammerman

The Jeffsy has a Flip Chip to switch between two geometry settings, an efficiency-oriented High setting and a charging Low position. We tested the Jeffsy in both settings. We measure the bikes to get apples-to-apples comparisons. The head tube angle is a mid-slack 66-degrees in Low and 66.2 in High. Short, 436mm chainstays keep the bike compact with a 1162mm wheelbase. A 578mm effective top tube makes for a relatively tight cockpit that is surprisingly comfortable for long days in the saddle. In the High setting, the 338mm bottom bracket gets your center of gravity down without threatening too many pedal strikes. The same applies to the 330mm Low setting. It's not breakthrough geometry, and it doesn't come together with that extra spark of special, but it works. The Jeffsy weighs 30lbs 12oz.


One of the YT's advantages is that cutting the cost of the middle man and leaves plenty of budget for a quality build spec. The Jeffsy is no different, with its Al One 29 build providing a rock solid spec. Even that tricky shock is a reputable one, and we're pretty sure we just got unlucky on our test bike.

yt jeffsy al one 29 2017 trail mountain bike review - the rockshox pike is the definition of reliable.
The RockShox Pike is the definition of reliable.
Credit: Jenna Ammerman

Fork and Shock — The 140mm RockShox Pike RC performs predictably, providing a stiff, responsive ride. We liked it.

yt jeffsy al one 29 2017 trail mountain bike review - our rockshox monarch quickly developed a sticky point approximately...
Our RockShox Monarch quickly developed a sticky point approximately 35% through its stroke.
Credit: Jenna Ammerman

The RockShox Monarch RT on the other hand quickly deteriorated during testing. It developed a sticky point or knock 35% into the travel. This hitch in the stroke annoyed us to no end on the climbs. We blew right through it on the downhills.

Wheels and Tires — A DT Swiss E1900 Spline wheelset provides sufficient but lackluster hub engagement. The 22.5mm inner rim width is much narrower than we'd prefer. The extra traction and cushion a wider rim, say 30mm, and some meatier tires would help this bike on the way up and the way down.

yt jeffsy al one 29 2017 trail mountain bike review - the onza ibex tires were respectable performer.
The Onza Ibex tires were respectable performer.
Credit: Jenna Ammerman

The Onza Ibex 29 x 2.4" tires were decent. These tires are similar to the Maxxis High Roller II in appearance and washy performance. These tires perform respectably dry conditions, and riders in wetter climates will be switching them out in a hurry. They also had tubes. We don't like tubes.

yt jeffsy al one 29 2017 trail mountain bike review - a sram x1 drivetrain is an awesome specification on a $3000 bike.
A SRAM X1 drivetrain is an awesome specification on a $3000 bike.
Credit: Jenna Ammerman

Groupset — As drivetrains go, the SRAM X1 11-speed is pretty hard to complain about, with high quality, crisp shifting. The gear ratio is odd for a trail bike though, with a 32-tooth chainring linking up to a 42-tooth cog to make for one stiff climbing gear. Jeffsy's granny's got legs. On the upside, the bike can certainly crank on the downhills and in the flats.

SRAM Guide RS brakes with a 200mm SRAM Centerline rotor up front and 180mm in the rear give you plenty of control and power in your braking. None of our testers, even the big ones, had any trouble shutting this 29er down.

yt jeffsy al one 29 2017 trail mountain bike review - we love the responsiveness of the 35.0mm bar/stem combo.
We love the responsiveness of the 35.0mm bar/stem combo.
Credit: Jenna Ammerman

Handlebars, Seat and Seatpost — The burly 35mm clamp on the 780mm RaceFace Turbine handlebars give tons of control while keeping a profile low enough to sneak through the trees with relative ease. A 50mm stem keeps the steering direct.

yt jeffsy al one 29 2017 trail mountain bike review - the e*thirteen trs+ dropper post had its cable snap out of the box...
The E*Thirteen TRS+ dropper post had its cable snap out of the box. Luckily, it is pretty easy to work with.
Credit: Jenna Ammerman

The SDG Fly Mtn saddle is fine, but the E*Thirteen dropper leaves reliability and performance to be desired. The cable actuated system has trouble finding its indexed stops, leaving you riding like an escaped merry-go-round horse, bobbing slowly up and down to find a lock. Tightly restricted external cable routing makes it very hard to adjust cable tension on the fly. On the plus side, it's easy to access for repairs. You'll probably need to.

Build Options

yt jeffsy al one 29 2017 trail mountain bike review
We rode the Jeffsy AL One 29 for $2,999. For $400 less, you can snag the Jeffsy AL Two, with the same tire and rim combo you get a slightly downgraded SRAM GX drivetrain with the good old dual ring setup, RockShox Pike RC fork, and slightly less adjustable RockShox Monarch R rear shock. This component spec is still excellent, and we say go for it if you can stand a front derailleur.

The carbon version of our bike, the Jeffsy CF One 29 is only $400 more at $3,399. It keeps the SRAM X1, and it gets you an upgraded fork, the RockShox Pike RCT3. Also, they upgrade the rear shock to the RockShox Monarch RT3. That's insane. This is an unprecedented value if you're dead set on carbon. The Jeffsy CF Two 29 carbon takes a similar step up but opts for a dual ring Shimano XT drivetrain.

The CF Pro 29 and CF Pro Race 29, $4,799 and $5,599 respectively, get into Fox shock and SRAM X01 territory. The Pro Race has the higher quality suspension components but the CF Pro is your only SRAM X01 Eagle option.

You can get any of these builds with a 27.5" wheelset on the same frame. We like that the 29-inch wheels add some forgiveness to this taskmaster of a bike, but we haven't gotten on a smaller wheeled version to date.


For $2,999 you get high-quality components on a reasonable frame with a very progressive rear suspension. This is an excellent immediate value, letting you start shredding trails on day one. It's also a great value if you like epic days on mainly smooth trails. If you're planning on tackling technical, this bike isn't going to make it easy for you. You may be better served investing in a solid frame with a not-so-solid spec and building it up over time.

Suggested Upgrades

First things first, set your tires up tubeless. All you'll need is some tape, valves, and sealant. Then take off that 32-tooth chainring and slap on a 28 or 30-tooth for some easier spinning. Or get real fancy with an E*Thirteen extended range cassette. The first option is a $50 fix. The second runs more like $300. A new dropper post could improve your riding experience. The KS Lev Integra is a popular, simple, and reliable option for $299 or so.

yt jeffsy al one 29 2017 trail mountain bike review - smooth trails + high speeds = fun aboard the jeffsy.
Smooth trails + high speeds = fun aboard the Jeffsy.
Credit: Jenna Ammerman


The YT Jeffsy isn't quite the hardcore trail slayer we anticipated. The AL One 29 build we tested makes for a reliable machine that successfully employs the physics of big wheels. The bike doesn't get hung up on rocks, and it rolls like the dickens, but still wraps around corners with ease. We just can't get behind the rear suspension, which never feels good over rock and is terrible on rapid-fire hits. On long rides though, the Jeffsy seems to step up its game just as you're losing yours. This bike can take on nearly any terrain. Still, the smoother the trail, the nicer the ride. If that's your style, the Jeffsy rolls in at a price point that's hard to beat.

Clark Tate, Pat Donahue, Joshua Hutchens, Curtis Smith

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