YT Jeffsy CF Comp 1 first ride review

New 140mm 29er trail bike with boost spacing in rear

29er All Mountain Trail
The author testing Jeffsy’s wings. Photo by Ale Di Lullo

The author testing Jeffsy’s wings (click to enlarge). Photo by Ale Di Lullo

YT Industries recently brought a Jeffsy fleet to Santa Cruz, California, and invited Mtbr to cast our verdict: love or hate. (If the former, then an #ILOVEJEFFSY social media post would be in order). Both Markus Flossmann (CEO) and Stefan Willared (CTO) were on hand to talk about the bike’s design, answer questions, and provide some colorful commentary about our riding while we tried to look good for the camera. Fortunately the location was our home base, so we got to ride Jeffsy on familiar territory. Continue reading to learn our final verdict on this new 140mm 29er trail bike.

Jeffsy CF Pro. Photo by Ale Di Lullo

Jeffsy CF Pro (click to enlarge). Photo by Ale Di Lullo

We’ve already posted a first-look at the Jeffsy, which covers general information about the bike’s geometry, builds, and target use. So we’ll skip the rehash except to say that the Jeffsy is a bit less than I generally ride (29er with 160mm travel). Now on to on-trail performance of the Jeffsy Comp 1 (white bike), which is what we tested. The red frame rig in some of the photos is the CF Pro.

Jeffsy CF Comp 1. Photo by Ale Di Lullo

Jeffsy CF Comp 1 (click to enlarge). Photo by Ale Di Lullo

The Jeffsy looks quite similar to YT Industries’ other two bikes, the Capra and Tues, which is a very good thing. The main difference is the link now attaches to the seat tube instead of downtube. Additionally, the downtube takes a less direct path to the bottom bracket, which improves aesthetics and provides a location for a water bottle cage. Cables are routed both internally and externally, with the rear derailleur cable traveling inside the downtube and chainstay, dropper cable inside the seat tube, and other cables external, secured to the frame using integrated mounts with zip ties.

2017 YT Jeffsy 2017 YT Jeffsy

Cable management and routing, down and seat tubes (click to enlarge). Photos by Ale Di Lullo

Utilizing the 148mm boost rear hub standard has allowed frame’s designers to improve the chainline for these large wheeled trail machines and add additional stiffness, particularly useful with the larger wheel diameter. An additional 3mm on the drive side might not sound like much, but given the clearance, it makes a huge difference. Boost is only in the back though, with the front retaining 100mm hub spacing.

SRAM and Race Face drivetrain. Molded chain stay protectors. Photo by Ale Di Lullo

SRAM and Race Face drivetrain. Molded chain stay protectors (click to enlarge). Photo by Ale Di Lullo

The bikes all look amazing, with the paint on the alloy version being particularly eye-catching (more of a flat look rather than glossy). Keeping the finish looking flawless is easier now, and there’s no more need for old inner tubes being wrapped around the stays. YT added not one, but three molded rubber protectors, located on the lower downtube and inside both the chainstay and seatstay.

Additional frame protection for chain drops was a stroke of genius. Metal pieces are located outside the cassette on the seatstay, on the front edge of the chainstay and on the upper portion of the bottom bracket — all the points of contact from chain drops. My personal bikes have scars in those areas, so I’m excited to see something functional to address it (that I didn’t hack together in the garage and have to worry about falling off and getting sucked into somewhere it shouldn’t be).

Continue to page 2 for more on the YT Jeffsy »
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About the author: John Bennett

With 210 lbs of solid, descending mass, John is a good litmus test of what bikes and components will survive out there in the real world. And with a good engineering mind, John is able to make sense of it all as well. Or at least come up with fancy terms to impress the group.


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  • Luca says:

    Improves steering response with less offset fork (44mm vs 51mm)?How?

    • wadeholiday@gmail.com says:

      this is one that seems to be tough, and often misinterpreted.
      In my experience and research less offset slow steering, improves carving/stability, more offset lightens the steering. some engineer can help us?
      Cheers.

  • JD says:

    Not trying to be the annoying proof-reader/fact checker guy, but the comments about offset are incorrect, and you aren’t the only site to mention this. a 44mm offset will increase trail #’s and SLOW steering in comparison to the same HTA on a 51mm offset. I should note, that I personally like this since it makes it more stable at speed, but this for sure bucks the trend of more offset on 29ers. thanks for the review – looking forward to riding this and comparing to the SC hightower

  • Stu says:

    How did you find the sizing on this bike ? at 5’10 I’d be looking at the large to get the reach figure that I want but the seat tube looks huge …. especially with a 150mm dropper post.

  • Alan says:

    I rode this at a demo day recently – I’m 5’11″ /180 and the L was just right – seat post up about 1cm from lowest position – my inseam is I think about 31″, but if that close you really want to try out – Capra has same seat tube length.
    And I agree on the fork offset – I found it quite sluggish to turn, compared with Canfield EPO with exact same fork the EPO has shorter chainstay so turns quickly and needs the stability of the long fork trail.

  • muf says:

    Ive a L jeffsy cf and a M HT.
    178cm to 184 or so id get the jeffsy L. In 180.
    The HT sizes a bit bigger though 180 on M is the limit IMO.

    The jeffsy is pretty great otherwise. Climbs better than the HT. HT descends better.
    Jeffsy is also a bit higher up specially on the front end.
    Easier to point the jeffsy where you want it than the HT which goes where ir decides.

    The thing is thou.. The HT is more enduroish and will blast through things where the jeffsy requires more skill. Heck the HT feels like a 27.5 while on 29 wheels. The jeffsy still feels like a 29.

    I like both and favor the HT at the end of the day because of how it deals with gnarly stuff more easily.

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