Sigma - Installation

Sigma X Installation Guide

  1. Begin by removing the headset cap and any round spacers already on your fork. The Sigma X is designed with aero-matched stem spacers and an ultra-low dust cap for superior aerodynamic performance. Depending on your headset, you may or may not need to install some or all of the micro shims just below the dust cap. Each micro shim is 0.25mm thick. Most headsets will not require them. However, if there is play in your system after installation, some shims may be required.
  2. The Sigma X can be used with any number of round spacers above the stem, allowing you to leave room to adjust your position upwards in the future if desired. The stem is designed for best aerodynamic performance when used with 10mm or less of round spacers above the stem. At a minimum, use a 5mm spacer (included with the stem), and trim your steerer tube so that it ends 2-3mm below the top surface of that spacer.
  3. With the cable cover removed, install the Sigma X onto your fork as you would any other stem. Follow the torque specification of your headset for the headset preload bolt (in general, just enough torque to remove any play from the steerer column). Apply carbon grip paste (such as Finish Line Fiber Grip) around the steerer tube, and all interior surfaces of the Sigma X stem clamping zone, including the wedge-style steerer clamp. Install the wedge-style steerer clamp assembly, and adjust the stem so that your stem is in line with the front wheel. Then use 15-18 Nm of torque on the single M6 socket screw in the wedge-style steerer clamp to tighten the Sigma X to your steerer tube.
  4. Apply carbon grip paste (such as Finish Line Fiber Grip) to the interior handlebar clamping area. Install your handlebars in the usual manner. Use 7 Nm of torque on the four M5 socket screws that tighten the handlebar clamp, or the amount of torque recommended by your handlebar manufacturer. As with any stem, you do not want to immediately torque any bolt to its maximum torque spec while other bolts are significantly looser. Instead, tighten each bolt just a little bit at a time, taking several passes to arrive at the final torque specification. Ensure that the gap between the top and bottom halves of the Sigma X stem is the same at the front and the back. Also, check the torque spec of the stem periodically to ensure that the bolts maintain torque over time.
  5. The Sigma X features integrated routing for use with centerpull brakes like the TriRig Omega X. This routing system features a removable cable stop so that you can either run bare cable to your brake with the stop in place, or run full housing or a hydraulic line by removing the cable stop. For installations with the cable stop, the optimal housing length will depend on your particular equipment, but for aerodynamic purposes, it's best to attempt to route the cable such that it hides behind the frontal profile of your handlebars. That is, attempt to route the front brake cable housing so that it is not visible when viewed from the front of your bicycle.
  6. Once the stem and handlebars are in place, use the cable cover to collect all the cables and hide them out of view of the wind. Use 2-3 Nm of torque on each screw to attach the cable cover to the stem. Depending on your particular setup, it may be advantageous to collect only some of the cables beneath the stem cover, leaving others outside. Because the cable cover is not a structural element of the Sigma, it can be removed or re-installed at any time for travel or adjustment purposes.
  7. The Sigma X cable cover also serves as an integrated BTA mount for easily attaching a bottle cage directly to the stem. In order to mount a bottle cage, first remove the two M5 bolts that attach the cable cover to the stem. Then install the bottle cage and cable cover together, running those same M5 bolts through both parts. The cable cover will essentially be sandwiched between the bottle cage and the stem. Use 2-3 Nm of torque on each bolt.

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.