The ST31 Carbon Stem isn't a stem you buy because you want to upgrade your cockpit — it's the stem you buy because your Cervelo frame demands it. The C-shaped (D-shaped) steerer tube on the Áspero-5, Caledonia-5, R5, and R5-CX requires a matching stem, and the ST31 is Cervelo's 8-degree-drop carbon option built for that interface. If your bike came with the alloy ST32 and you want to shed some grams up front while keeping the factory cockpit lines, this is the direct swap — and at 90mm, this one lands right in the middle of the fit range for riders who don't want to stretch out or sit up.

Construction is unidirectional carbon with a 4-bolt faceplate sized for 31.8mm handlebars and a 2-bolt steerer clamp that uses a split spacer system , so you're not locked into Cervelo's HB13 bar if you'd prefer something else. The 8-degree drop sits the bars below the stem clamp in a position that works for most road and gravel fits. Internal routing passes Di2 wires and hydraulic hoses from the handlebar face into the steerer tube, keeping cables hidden from view and out of the wind , and the integrated top cap closes off the steerer opening so wind doesn't catch the gap.

The split spacer system is required for installation — generic spacers won't work with the C-shape interface, so plan on sourcing the SK-023 spacers if your build doesn't already have them. The faceplate also works with Cervelo's BarFly system for easy mounting , which means a clean computer mount without aftermarket adapters cluttering the front end.... Read More