The Specialized Stumpjumper has spent four decades as the bike the rest of the range is measured against. But the modern story — the one written in linkage geometry rather than marketing copy — really starts with the 2021 Stumpjumper EVO and runs through to today's Stumpjumper 15. Across those generations Specialized quietly rewrote how the bike squats, supports and tracks the ground.

This is that story, told through the kinematics.

Four decades is easy to write and hard to picture, so here is the other end of the timeline — scans from the original 1994 Stumpjumper owner's manual. Long before adjustable headsets and flip chips, the whole bike fit on a few printed pages. Flip through them below.

The Stumpjumper EVO arrived with the adjustable headset cups and the flip chip everyone remembers — but the more important change was under the shock. Its leverage curve traded the old, flatter Stumpjumper ramp for something more progressive, giving the bike enough bottom-out support to run a coil or a lightly-tuned air shock without blowing through travel.

That progression is what let one frame straddle trail and light-enduro duty. The axle path tells the other half of the story: a touch more rearward travel early in the stroke than a pure trail bike, helping the rear wheel get out of the way of square-edged hits.

The Stumpjumper 15 isn't a reshuffle of the EVO — it's a genuinely different linkage, built around Specialized's Genie-influenced thinking about support and usable travel. The headline is how much more the curve does the work that the shock tune used to: more end-stroke ramp, a different early-travel rate, and an axle path retuned for the longer, slacker front end.

The fastest way to see it is to put both generations on the same axes.

Read the two curves together and the design intent jumps out: where the EVO ramps steadily, the 15 holds a flatter mid-stroke for traction and small-bump sensitivity, then ramps harder at the end to recover the bottom-out support. That's a setup that wants a different spring and a different volume-spacer count than the EVO ever did.

Here's the workflow end to end — overlaying both generations and reading off the differences live in the analyser.

Numbers aren't the point on their own — the point is that you can now see, side by side, the choices Specialized made between two bikes that share a name and almost nothing else under the rocker. Drop your own Stumpjumper into the analyser and overlay it on these curves to see exactly where your setup sits in the lineage.