PRO Tharsis Trail Stem

PRO Tharsis Trail Stem Info

The PRO Tharsis Trail Stem is shorter, stouter brother to the Tharsis XC stem.

Besides, the attractive design--and light thanks to the 7075 aluminum used in forging--the stem comes with an external headset adjuster and top cap. Weight is 95g for the 35mm length.

It’s a cool fix on its own. This way, you don’t need a star-fangled nut or expander plug inside your steerer tube. You can just put the stem on, push it down on top of the top cap or stack spacers, tighten the steerer tube clamp bolts to the recommended torque (5Nm), and then use the adjuster, a dial under the stem, to take out the play, and secure that. Push on the included top cap and you’re done. All the same, for security, the BTR expander, a combined expander nut and battery hanger, are included.

But the second reason for this is because you can now, if your steerer tube is at over 152mm deep, install a Di2 battery, if you’re running Shimano Di2 shifting, inside the steerer tube. PRO has options for this install, including Di2-compatible handlebars and a clamshell you put around the battery and push into the steerer. A great hiding place, and very easy to service if need be. You won’t have to mess with your saddle position, which is usually far more sensitive than your handlebar position. That’s why the top cap is designed to be pushed on: you route the Di2 wire through and over the stem and into the steerer.

Then, there’s the stem itself, which is pretty impressive. 7075 aluminum, with titanium bolts, the 35mm long version comes in at a light 95g. The stem is available with a zero-degree angle (aka 90-degrees to the steerer tube it is clamped to. It is available in lengths from 35-65mm in 10mm increments.

The PRO Tharsis Trail Stem gives you the option to hide your Di2 battery inside the steerer.