Clean routing while cleaning lines.

Given that it shares the corporate family tree with Shimano, it's no surprise that PRO developed cockpit kit that allows for clean, flawless routing of the new XTR Di2. PRO's calling this system Tharsis, and the Tharsis XC Stem is one of the two key ingredients.

As PRO's own Bas Schaapveld describes it, the Tharsis stem and handlebar combination is a "showcase for Shimano" to demonstrate the possibilities of not only clean shifting and routing, but the simple elegance of a drivetrain and cockpit designed to interface seamlessly. In addition to the internal routing, this interface also involves a clamping system that ditches the usual star nut in favor of a threaded spacer that compresses the stack, leaving the steerer tube free to house a Di2 battery.

The internal, intuitive Di2 routing is only part of the Tharsis XC Stem's story, though, as its lightweight alloy and titanium bolts keep the claimed grams under 145 for the 100mm option. It's also stiff enough for XC sprints and durable enough to survive standard trail abuse and the occasional instances when a bike gets a little too intimate with a passing tree. After all, clean lines and stylish routing are useless if the kit wilts at the first sign of trail furniture, and the Tharsis models were developed in conjunction with the riders on Shimano's sponsored XC teams to ensure that their fortitude matches their style.

  • Reviews
  • Q & A

Unable to Preload

  • Familiarity: I've put it through the wringer

The threaded spacers that compress the stack does not work, no matter what there is a little bit of play within the stack.

Tried 2 of these stems, first one i tried so hard on the 32mm threaded spacers, it stripped the head. On the second one, same problem, with play within the stack.

Not sure what went wrong here with Peter C.'s stem, but I was able to get a good preload with this stem. The problem arises when using a carbon steerer tube - the clamp concentrates the force too much and starts to collapse the tube. For aluminum steerers only I guess.

missing part

    received part and one of the screws for the front plate was missing