If you follow World Cup XC racing (and you should, it’s savage) you may remember the conspicuous black coverings wrapped around the toptubes of certain Trek bikes throughout the 2019 season. Speculation ran rampant. What was under there? Was it a version of the IsoSpeed decoupler carried over from Trek’s drop-bar bikes? Was it some sort of mini-shock? The answer, as it turns out, was exactly as weird as we’d all hoped.
Trek’s new Supercaliber features a proprietary 60-millimeter Fox shock, which couples the seatstays directly with the toptube. Dubbed IsoStrut, the frame-integrated shock houses the mounting hardware inside the toptube, cutting weight and supporting the stanchion through the full travel. This helps eliminate any deflection or rotation, and shaves off a whole bunch of material in the process.