Sigma - Features

Sigma X is a brand new way to look at your front end fit. Everything about the stem, from its low frontal area to its aero-matched spacers and hidden bolts, was designed to cheat the wind while still allowing standard adjustments and easy cable routing. Developed in tandem with Alpha X, it was born and bred to provide superbike aerodynamics with standard bike convenience. That's why we call it the Superstem.


Tiny frontal profile

Single piece construction greatly reduces frontal area. There is no extra bulky mounting hardware to join the stem and bar together. The Alpha X is made of carbon fiber for the lightest weight and highest stiffness, while maintaining smooth shapes in all directions to completely minimizes drag.

Hidden Bolts, Low Bolt Count

Not one millimeter of any bolt is exposed to the wind, to promote smoother airflow and reduce drag. And we keep the bolt count to an absolute minimum, using a single-bolt wedge-style stem clamp. And the two Cable Cover bolts serve double-duty as an optional BTA mount.

Fit + Adjustment

The Sigma X isn't just fast, it's also a champion of good bike fit.

Adjustable and Re-Adjustable

One of the biggest problems with modern high-end aero equipment is that, once you've installed it, it becomes very difficult to change your position. On integrated solutions, you often have to buy extra stems or an entire new bar just to adjust your position by 10-20mm. With Sigma X, adding stack and staying aero is all part of the game, thanks to the aero-matched spacers. Want to go up 10mm? Just loosen two bolts, slide on the spacer, and you're done.

All Hardware Included

The Sigma X comes complete with 40mm of aero-matched fork spacers. No need to buy anything extra in order to achieve that perfect fit. And the bolts for the stem cover double as an integrated BTA mount - attach your bottle cage without a single zip tie, velcro strap, or other extranneous hardware.

Complete Fit Solution

The Sigma X isn't just a stem. It's part of a complete front-end solution that can truly get you dialed while keeping your setup clean and aero.

Aero-Matched Stem Spacers + Ultra-low Dust Cap

The Sigma X includes the same aero-matched spacers and ultra-low dust cap as our full Alpha X cockpit, for superlative aerodynamics. The bottom channel allows you to run centerpull cable routing or full housing with ease, and their split-back design means they can be added or removed without re-cabling. Our ultra-low 1mm dust cap is also included, meaning you can replace all the non-aero equipment your bike came with, and upgrade to superbike status.

No Fork Cutting Required

The cable cover of the Sigma X works even when the steerer is long. This allows you to fully build your bike and try out a different number of spacers before having to commit to a steer tube length. And the first 10mm of spacers above the stem are still shielded from the wind. This helps down the road if you ever need to come back up, or want to preserve resale value for your bike. No more need to trim the fork in the name of aero.

BTA Mount Included

Every Sigma X includes our integrated BTA hydration mount, putting the bottle in perfect position without adding the huge frontal area from an aftermarket solution. No straps, no zip-ties, just a bolt-on solution that keeps your bottle rock solid and right where you need it.

Cable Management

Hassle-Free Routing

Thanks to the Sigma X cable cover, hiding your cables from the wind is trivially easy. Just route your cables as normal, and then after the job is done, use the cable cover to collect them and hide them from the wind. No need to attempt a convoluted cable path just to keep things clean. And because the cable cover is not structural, it can be added or removed at any time, no fuss required.

Center-pull Cable Stop

The Sigma X comes with a removable centerpull cable stop. If you use a center pull brake like the TriRig Omega X, you can route to this stop and run bare cable from there to the front brake for the cleanest possible setup. Or, simply remove the stop and run full housing or a hydraulic line to any other brake you want. The Sigma X makes for a super-clean setup with anything.

Minimal, Simple, Light

All-Carbon Construction

The Sigma X is now made of carbon, saving significant weight compared to its predecessor, and improving stiffness dramatically. This isn't merely an aero stem, it's a road biker's dream thanks to its rock-solid platform. Sigma X is the perfect stem not only for triathletes, but for sprint-loving roadies and breakaway specialists alike.

Single-bolt Wedge style steerer clamp

The Sigma X features a novel wedge style steerer clamp. This utilizes just ONE bolt, stays COMPLETELY out of the wind, and is easy to use and adjust. Sigma X is the first road stem to use this tech, and once you see it, you'll wonder why it was ever done any other way.

Fit Guide

This Guide shows you how to set up your TriRig Omni with the TriRig Alpha One or Alpha X aerobars. This Guide can help you replicate your current bike position, or set up your bike based on numbers from a bike fitter. The Fit Chart below shows the actual X/Y coordinates of your arm pads measured from the bottom bracket. This coordinate is the most important number that bike fitters use to determine your position on a triathlon bike. Be aware that some fitters use a coordinate to the top/back of the pad, rather than the top/center. In that case, you can subtract 44mm from all of the reach numbers in the Fit Chart, which yields the back of pad number. The steps below provide an easy-to-follow system for making sure you have the perfect fit with your Omni.

Step 1: Determine your current fit numbers

What we want is the X/Y coordinate to the top/center of your aerobar pads, measured from the bottom bracket. Most bike fitters can provide this number to you when performing a bike fit (although some provide it to the top/back of the pads rather than top/center). If you already know these numbers, you can skip this step. Otherwise, follow the steps below to determine these numbers for your current bike setup:

1-Place your bicycle up against the corner of a room, with the back tire abutting the wall.

2-Next, measure the vertical distance from the floor to the center of the bottom bracket. We'll call this measurement Floor Offset (FO).

3-Measure the horizontal distance from the wall to the center of the bottom bracket, we'll call this measurement Wall Offset (WO).

4-Measure the vertical distance from the floor to the top of your aerobar pads. This measurement will be Pads-To-Floor (PTF).

5-Measure the horizontal distance from the wall to the center of your aerobar pads. This will be called Pads-To-Wall (PTW).

6-Subtract Floor Offset from Pads-To-Floor (PTF minus FO). This is your Pad Stack.

7-Subtract Wall Offset from Pads-To-Wall (PTW minus WO). This is your Pad Reach.

Step 2: Review Frame Geometry

Small Medium Large
Frame Stack
(BB to Headset)
490mm 525mm 560mm
Frame Reach
(BB to Headset)
375mm 405mm 435mm
Front Center 560mm 600mm 640mm
Rear Center 400mm 400mm 400mm
Seat Angle 79° 79° 79°
Head Angle 72.5° 72.5° 72.5°
Fork Offset 48mm 48mm 48mm

Step 3: Select Size, then find your position on the chart

The chart below shows the stack and reach information for the TriRig Omni with the included Alpha X aerobar, complete with the number of extension spacers and stem spacers used for each setup. Here's how to use the chart:

1-Use the dropdown box in the upper-right corner of the chart to select a bike size.

2-Find your Stack in the left-hand column of the chart, or the row that most closely matches your stack. Every cell in this row represents a way to set up the Alpha X on your Omni that will produce this stack number.

3-Each cell states the amount of Pad Spacers as well as Stem Spacers to use in order to hit your stack number.

4-In most cases, there will be multiple cells that can hit your stack. The best setup for your position will generally be the one with additional colored cells above AND below your selected cell. These cells represent room to move up or down in the future, merely by adding or removing Pad Spacers, which is generally the easiest way to make a position change.

5-Cells in blue represent a standard setup with the extensions over the bar. Cells in green represent the special undermount position, where the extensions are mounted below the bar.

6-Once you have selected a cell from your Stack row that represents your preferred position, look at the bottom of that column to the Reach section. The three rows of Reach cells show the reach to the center of the pad based on the three different adjustment positions available on the Alpha X arm cups. Select the one that most closely matches your Pad Reach number, and set up your pads/cups accordingly.

7-Note that fit numbers for the Omni w/ Alpha X are measured from the top/center of the headset to the top/center of the pad. All measurements for overmount hardware include the integrated BTA mount.