2017 YT Jeffsy CF 27 Pro

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The wheel size debate is a dead horse beaten into mushy glue by this point. The hatred forged by some toward 29ers is likely rooted in experiences from a time when the only options were Gary Fisher hardtails. The market has matured, and frame, wheel, suspension, and tire selection have come a long way. 27.5 and 29-inch bikes are different tools that excel in different ways. That being said, this tester has a hard time wrangling many 29ers. Remember how Danny Hart had a skid mark up his ass for the first half of the 2017 season? That skid mark is how some of us feel on big wheels.

This past February, YT introduced the Jeffsy 27. It looks a lot like its brother the Jeffsy 29, a bike we've reviewed in detail before, and from a quick glance you might find the two difficult to tell apart. So why did they make a 27.5 version? Was it just because some people are so resistant to accept a wheel size? We set out to find what the new ride had to offer aside from smaller hoops and the appeal of high-value, direct-to-consumer sales that the brand made popular in the mountain bike world.

Strengths

• Incredible value
• Ultra-progressive suspension design gives it a playful, bottomless feel with good off the top traction
• Ability to increase rear travel with a shock swap
• Externally routed rear brake
• High-end build kit that won't leave you wanting
• Ships to your door

Weaknesses

• Limited to miniature water bottle size
• Occasional harshness over medium size bumps at speed
• Not a standout in the climbing category
• Outdated front fork and hub axle standard
• Seat tube lengths may be a bit too tall for some
• Requires minimal assembly

YT Jeffsy CF Pro 27 Highlights

• Carbon fiber frame
• 27.5-inch wheels
• 150mm (5.9-inches) of front and rear wheel travel
• Virtual 4-Link (Horst) suspension design
• Tapered headtube
• Internal cable routing for shifter (partial) and dropper (full) // External for brake
• Dropout chain suck guard
• Integrated frame protection
• 180mm rear brake post mount
• Coral red and jet black paint/graphics look fast as shit
• 92mm GXP press fit bottom bracket with ISCG05 mounts
• Boost 148mm rear spacing with 12mm through axle, non-Boost 15mm front
• Measured weight (size Medium, no pedals): 27.8-pounds (12.6kg)
• MSRP $4,799 USD

Just like the Jeffsy 29, the finer details are pretty dialed on this ride. With exception to the cute little sippy cup of a water bottle and a non-Boost front axle, the bike checks all of the key specification boxes that many of today's riders are after.

The Boost-spaced rear end moves through a familiar Horst style linkage that YT refers to as their Virtual 4-Link suspension design. Suspension characteristics that were generally well received were transplanted over to the new model. Like all YT bikes, the layout is progressive enough that running a coil shock is perfectly doable:

The model we tested comes paired with a Metric-sized 230x60mm FOX Float DPS Performance Elite air shock, providing 150mm of travel. Those looking for a little extra party can move to a longer stroke 230x65mm shock – which YT does on the highest end CF Pro Race build – to get an additional 10mm of bump-eating capability.

With exception to the cute little sippy cup of a water bottle and a non-Boost front axle, the bike checks all of the key specification boxes that many of today's riders are after.

The shock and pivots are all out in the open and easily accessible. Every bearing is sealed for longevity, and the use of two bearings on the driveside of the main pivot bodes well for that crucial area.

YT says they've made the "high modular" carbon fiber tube walls "thicker in critical areas to make sure the frame can handle the abuse, and integrated protectors keep the downtube and chainstays out of harm’s way when the action heats up." The polyurethane downtube guard is a bit on the small side, but it's there nonetheless. We dig the small aluminum protection plates located on the frame near the chainring and cassette to prevent frame damage should the chain derail.

Jeffsy frames use a mixture of internal and external cable routing that is clean and well thought out, with the rear brake remaining entirely external for easy maintenance. Small guides ensure the rear derailleur cable and small portion of internal dropper routing stay quiet inside the frame.

The Jeffsy 27 comes with ISCG05 tabs in case you get extra rowdy and start trying to throw your chain off into the woods. For those that choose to throw more chains, a removable e-type adapter can be added to mount a front derailleur.

With a total of six models to choose from, including two aluminum and four carbon versions ranging from $2,599 to $5,599 USD, YT has a Jeffsy 27 to fit a lot of budgets.

Geometry

Perhaps most importantly, YT lengthened the reach 15mm across the entire size run of the Jeffsy 27 compared to the Jeffsy 29, bringing it up to speed with the competition and making bikes that will fit a wider range of rider heights.

The bike feels lively and light due to the playful nature of the suspension. While that might mean feeling a bit more feedback from the trail, some will prefer this to the perceived heavy feeling of a bike that spends a lot of energy trying to gobble every bit of terrain imperfection.

The bike feels lively and light due to the playful nature of the suspension. While that might mean feeling a bit more feedback from the trail, some will prefer this to the perceived heavy feeling of a bike that spends a lot of energy trying to gobble every bit of terrain imperfection. Rolling speed is well maintained by the bike, especially with pumping input translating effectively into moving the bike forward.

Though this tester is admittedly a terrible jumper, the Jeffsy 27 provided a stable and predictable response to lips (versus something like the original Santa Cruz Bronson where every jump was a roll of the dice with your life). It handled steep roll-ins thanks to the slack head angle and dove with confidence into corners. At 5'7" (1.70m) tall on a size medium frame, it swapped direction in alternating turns quickly – something this tester has struggled with on comparably sized 29ers of any brand.

The only geometry beef we had is one we also had with the Jeffsy 29. Even when slammed against the seat collar, the 150mm travel Race Face Turbine dropper post was a hair too tall for shorter testers on an otherwise glove-like fit. Swapping to a 125mm dropper post would fix this, we just had to be mindful that full seatpost extension meant a few millimeters too tall of a perch to keep the loins happy.

Initial impressions for climbing held true throughout the testing period. The steep 75-degree seat tube angle put us in a comfortable climbing position that kept the front end from wandering too much while still providing traction to the back end. It’s a good thing the shock has a quick-adjust compression lever, however, as it's helpful on steep, sustained climbs. The first bit of travel after sag is quite active, and with the shock wide open you’ll be losing some effort to the suspension. In the middle compression setting the bike stays much more steady and will reward you for sitting and spinning up a climb. If things call for it, short bursts out of the saddle are effective at getting the bike to punch up techy parts of a climb without blowing out all your energy. Full lockout mode was only used as a novelty on the road to the trail one time. The bike climbs appropriately for a 150mm trail/all-mountain bike, but it isn't a standout in the climbing category.

Build Kit

YT is well regarded for offering component specs that are great values and sensible choices. It’s clear that they do their homework on choosing what an educated rider would want for a given budget. The $4,799 CF Pro build we tested leaves little that could be improved upon without substantial investment, and the parts you get out of the box will keep you rolling happy for a long time. The choice to go non-Boost up front may make fork upgrades a few years from now more difficult, however, though there are some aftermarket hub conversion options available.

YT chose to spec this bike with the FOX Float DPS Performance Elite air shock with an EVOL air sleeve and FOX 34 Float Performance Elite fork up front, giving you 150mm of travel on both ends. The Performance Elite series features the exact same internals as FOX's Factory series, minus the Kashima-coated stanchion tubes. The move to give you the upper end internals and save money on the glitz of Kashima is a welcome budget sacrifice. Can you really feel the few percent slicker performance on the trail? Probably not as much as you can feel the extra few hundred dollars in your bank account that could easily fund a ride trip.

We ran the fork slightly stiffer than where we would normally run it, which felt more balanced with the progressivity of the back end. Keeping the front air spring a bit stiffer and more open on both compression and rebound damping seemed to allow the fork to ride higher in its travel. A FOX 36 or a RockShox Lyrik would be a more capable fork for some of the rougher trails we rode, but would come with weight and budget penalties. The 34 surprised us with what it could handle, and if you need more the Capra might be a better bike for your needs.

YT is well regarded for offering component specs that are great values and sensible choices. It’s clear that they do their homework on choosing what an educated rider would want for a given budget.

As we've come to take for granted, the Maxxis High Roller II EXO casing tires provided a good balance of weight, traction, and rolling speed. YT specs the bike with a firmer 60a rubber compound on the rear tire for better durability.

e*thirteen's TRS+ wheels delivered on being reliable and cost appropriate. The loud rear hub comes with the association of a much more expensive wheelset, but it’s not all talk. The fast engagement was great to have when ratcheting our way through tricky climbs or getting on the gas after blowing a corner. They came setup tubeless on our bike, and we suffered no flats or burps during the test (knock on wood). By the end of the test they weren't perfectly round but could still be trued to a very good tolerance.

SRAM’s super adjustable Guide RSC brakes didn’t suffer from any of the previously known issues associated with these brakes and performed well throughout. The wise choice of a 200mm rotor up front meant plenty of power was on tap when paired with the still capable 180mm rear rotor. We only dealt with minor fade on the longest of descents and even that was quite manageable.

The 12-speed SRAM X01 Eagle drivetrain never dropped a chain, skipped a shift, or left us wanting. This drivetrain performs better and lasts longer than the previous 11-speed options from SRAM.

The bike is quiet down the trail with the exception of the buzzing rear hub. The only part that was changed for the test was the SDG Fly Mountain saddle which was swapped out purely for subjective preferences.

Long Term Durability

Some of the rubber frame guard material has started to lift on the chainstays due to heel rub, but this is nothing that some tape or glue touchups couldn’t fix. The downtube has sounded off a few dreaded rock strikes with no observable damage, and the finish has held up quite well with only minor blemishes. There are a few chips in the finish near cable entry/exit ports, however.

We performed two bolt checks more out of curiosity than anything else and found nothing loose in the pivots. We never had any suspension squeaking or odd frame noises. Though press fit bottom brackets have a poor track record, this one never creaked. A season of wet riding might have produced a different outcome, but we had no issues.

So long as you keep up with regular maintenance, we have no qualms saying this bike should provide you with years of reliable riding. YT provides a handy exploded diagram to make pivot service easier. The bike is backed by a three year warranty (five in the US) and crash replacement program.

What's The Bottom Line?

The main word we kept coming back to through the course of the test to describe the Jeffsy 27 was FUN. It encourages the kind of exploration and hootin' and hollerin' in the woods that still defines the mountain bike experience for us after all these years.

It’s not plush, but it’s not harsh. If you’re a passive passenger there are better bikes for you. The Jeffsy 27 requires you to push it a little to really show off its potential.

Regardless of what you feel about wheel size, the geometry adjustments made to the 27 version of the Jeffsy are good tweaks over the 29 version, making this a great option for anyone looking for a 27.5 trail bike. While it might not be the best enduro race machine for those purely concerned with hunting speed, you would be hard pressed to find a better everyday trail ripper, especially for the money.

Visit www.yt-industries.com for more details.

Vital MTB Rating

• 
  Climbing: 3.5 stars - Very Good
• 
  Descending: 4.5 stars - Outstanding
• 
  Fun Factor: 5 stars - Spectacular
• 
  Value: 5 stars - Spectacular
• 
  Overall Impression: 4.5 stars - Outstanding

About The Reviewer

Kevin Shiramizu - Age: 32 // Years Riding MTB: 20 // Height: 5'7" (1.70m) // Weight: 170-pounds (77.1kg)

During the two decades Kevin has been riding mountain bikes he accumulated multiple state championships in Colorado for XC and trials riding, a Junior National Championship title in trials, and went to Worlds to get his ass kicked by Euros in 2003. His riding favors flat corners and sneaky lines. After a doozy of a head injury, he hung up the downhill bike for good in early 2010 and now foolishly rides a very capable trail bike with less protection and crashes just as hard as ever. He likes rough, technical trails at high elevation, but usually settles for dry, dusty, and blown out. He spent five good years of his youth working in bike shops and pitched in efforts over the years with Decline, LitterMag, Dirt, and Vital MTB. He also helped develop frames and tires during his time as a guy who occasionally gets paid to ride his bike in a fancy way in front of big crowds of people.