Jeffsy

The Jeffsy range is split into six completes across aluminum and carbon, with pricing running from roughly $3,000 to the mid-$6,000s in the US. Core 1 and Core 2 are aluminum, then carbon appears from Core 2 CF upward, with the carbon frame bringing the STASH downtube storage. All builds share the same wheel size and the same core travel format, so the riding differences are primarily down to suspension, drivetrain, and wheels.

At the entry point, Core 1 AL uses Marzocchi suspension, Shimano Deore shifting, and SRAM DB8 brakes with 200mm rotors, and it’s also the heaviest build listed. Core 2 (in both AL and CF) is the first big step in suspension with a Fox 36 Performance fork and Float X Performance shock, and it also brings higher-end brakes (Hayes Dominion A4) and DT Swiss wheels; it’s a meaningful jump if you care about damping quality and braking feel.

Core 3 steps into Transmission with SRAM’s T-Type drivetrain and moves to Crankbrothers Synthesis Enduro alloy wheels, while Core 4 CF goes further with Fox Factory suspension and SRAM X0 Transmission plus lighter wheels. Value calls in the reviews tend to cluster around Core 2 for riders who don’t need carbon storage, and Core 3/4 for those who want the carbon frame features and the cleaner, higher-end control from the drivetrain and suspension upgrades.

Across reviews, the Jeffsy Mk III tends to be described as easy to settle into, with a ride character that prioritizes calmness and traction over a hyperactive, ultra-pop feel. BikeRadar sums up the shift from prior versions as “calmer, faster and more composed” (BikeRadar), and Pinkbike frames the appeal around “easy and intuitive handling” (PinkBike). On mixed terrain, that translates to a bike that will do long climbs without feeling like a pure gravity tool, then carry speed and stay quiet when trails get rougher.

Suspension feel comes up repeatedly. MBR called it “pillowy” at the recommended 30% sag (Mountain Bike Rider), while The Radavist highlighted an “isolated” sensation at speed until tuning brought more feedback (Theradavist). Several testers noted that setup changes can meaningfully alter the bike’s character, and that the Jeffsy’s supportive tune helps it avoid wallowing even with a fairly active feel.

The main tradeoffs are familiar for this category. Weight is repeatedly mentioned, especially on higher-spec builds, and a few reviewers wanted more stability when pushing very steep or very fast trails. Off-road.cc found it could feel “skittish at speed” with the stock front-end numbers and short rear center (Off), and Singletrackworld fixated on the “65° head angle” as the limiter on steeper descents (Singletrackworld). Others, riding different terrain and setups, were less bothered, which is a hint that rider style and local trail speeds matter as much as the spec sheet.