The Stumpjumper Evo, by a meaningful margin. Tier-matched, the carbon 15 EVO Expert (Shimano XT Di2) weighs 14.48 kg in the medium-equivalent size, while the Fuel EX 9.8 XT Di2 comes in at 15.08 kg in size M — about 600 g.

Drop down to the alloy builds and the gap widens dramatically. The alloy 15 EVO Comp Alloy is 16.55 kg; the alloy Fuel EX 8 is 16.89 kg, and reviewers measured production samples closer to 17 kg. For long pedaling days, the Evo's the easier bike to live with.

Both run 145 mm of rear travel. The fork is where they diverge — the Stumpjumper Evo ships with a 160 mm Fox 36 on sizes S2–S6 (150 mm on S1), while the Fuel EX runs a 150 mm fork stock.

That 10 mm fork difference matters. The Evo runs slacker dynamic geometry, sits the rider further back, and absorbs bigger hits up front. If you want the Trek to match, you'll need to step up to the Fuel LX (160 mm front and rear) — a separate model that uses the same frame but a different linkage and shock mount.

Specialized partnered with Fox to build a dual-chamber air spring. For the first ~70% of stroke, the shock breathes into a large outer air sleeve, giving a supple, almost coil-like initial feel. Past that point, an internal "GENIE band" closes off the outer chamber, drastically shrinking the air volume and producing a sharp end-stroke ramp.

The result, per Flow Mountain Bike: "never able to hit full travel despite all of my awful line choices and ugly hucks-to-flat." Some reviewers found the stock setup a touch too soft mid-stroke for aggressive riding, but Specialized ships extra GENIE bands that let you firm up the outer chamber's volume — up to four bands, each adding mid-stroke support.

Yes — that's the platform pitch. The same frame ships as the Fuel EX (145 mm), Fuel MX (150 mm mullet), and Fuel LX (160 mm enduro). To convert, you swap the rocker link and the lower shock mount.

It is not a flip-chip job. MBR and Flow noted the conversion requires buying additional hardware (rough numbers from the AU market: ~$240 for the link and ~$56 for the mount), and depending on which direction you go, you may also need a new fork or fork internals plus a different shock. Real, but more involved than a 30-second trailside swap.

Both punch above their travel. The Stumpjumper Evo uses anti-squat around 105–108% at sag and a 77° effective seat angle (76.5° on S4–S6) to keep the rider centered. Reviewers praised "all-out grip" on technical climbs thanks to the GENIE's supple initial stroke, though some noted the active rear can feel "wallowing" on smooth, sustained efforts — the two-position climb switch helps there.

The Fuel EX is steeper-seated (~78.6° effective on Small, 77.4° on Large) and uses a flatter anti-squat curve plus Trek's ABP. MBR found the climb-mode switch unnecessary; the bike pedals well in open mode. The catch is mass — the Trek climbs efficiently for what it weighs, but the Evo simply weighs less.

Both clear modern wide trail rubber. The Fuel EX's recorded clearance is 63.5 mm (~2.5"), and it ships with 29x2.5 Maxxis Minion DHF/DHR II on the M-and-up builds.

The Stumpjumper Evo ships 29x2.4 Butcher/Eliminator stock — also 2.5"-class compatible. Neither bike is the limiting factor; tire choice and casing weight matter more for trail character than the frame's max clearance.

Yes. Specialized removed cable routing for mechanical drivetrains from the FACT 11m carbon frame. All five carbon Evo builds run SRAM AXS or Shimano XT Di2 — wireless or wired-electronic. If you want mechanical Shimano, the alloy 15 EVO Alloy Comp is your only option on the Stumpjumper side.

The Fuel EX has no such restriction. Both alloy and carbon Trek frames retain mechanical routing, and the lineup includes mechanical XT, mechanical Deore, and mechanical SRAM Eagle 90 builds across the price ladder.

Both frames carry a lifetime warranty to the original owner against manufacturing defects. Specialized adds lifetime pivot bearing replacement on the Stumpjumper Evo, which is unusual at this price point.

Trek's lifetime warranty is partly transferable to a second owner (per Flow Mountain Bike), which is a tangible resale-value advantage on the used market. Both brands offer crash-replacement pricing on damaged frames.