Fit Guide
This page is a dynamic tool that will show you the stack/reach of Alpha One on YOUR particular bike. This Guide can help you replicate your current bike position on Alpha One, or set up a new bike with Alpha One based on numbers from a bike fitter. This Guide contains a database of the stack/reach numbers for most modern triathlon bicycle frames, as well as the actual stack/reach numbers for Alpha One. The Guide combines these numbers to produce a chart of actual X/Y coordinates of your 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. The steps below provide an easy-to-follow system for making sure you have the perfect fit with Alpha One aerobar.
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: Select your bike
Use the form below to pick your bike model. If your bike isn't in the list, you can input the frame geometry directly in the "Stack" and "Reach" fields. If you leave these blank, the fit chart will show the stack/reach information for Alpha One alone.
Frame Reach (to Headset):
Step 3: Find your position on the chart Show instructions
The chart below shows the stack and reach information for Alpha One, complete with the correct position of the Monopost, and the appropriate Stem Spacer used below the aerobar, for each setup. Note that Alpha One includes four different Stem Spacers, in 10mm, 20mm, 30mm, and 40mm stack heights. Only one spacer should be used (do not combine spacers). Here's how to use the chart:
1-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 Alpha One that will produce this stack number.
2-Each cell states the position of the Monopost, as shown by the numbers and hashmarks on the back of the Monopost, as well as the appropriate Stem Spacer to use in order to hit your stack number.
3-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 adjusting the Alpha One Monopost. This can be done by loosening the single bolt at the front of the bar, and is by far the fastest and easiest way to make a position change.
4-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 Alpha One's included Ergo Cups. Select the one that most closely matches your Pad Reach number, and set up your pads/cups accordingly. Note that even if the reach is not a perfect match, that may not make a significant difference to your fit. Our Ergo Cups are longer than most other pads, at 115mm front to back. That means that even if the center of the cup is slightly different from where you are used to, the additional length of the cup might support your arms the same way as a shorter cup would. As long as your shifters are adjusted to the same position, and your pads are at the same height, your body position will remain the same.
5-Alpha One is meant to be used without the headset dust cap and round fork spacers that came with your bike. Instead, both Alpha One's base bar and its integrated Stem Spacers feature an integrated dust cover that means you can remove the one included with your bike. This is how the Fit Guide below was measured, and also makes for the most aerodynamic setup.
6-Note that fit numbers for the Alpha are measured from the headset to the top/center of the pad. Some fit systems measure to the back of the pad. If your fit numbers are measured to the back of the pad, add 60mm to your stated reach number to get to the pad center for Alpha One.
Pad Stack (BB to Top of Pad) |
TriRig Alpha One (bar only) | ||||
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175mm | Monopost: 8, 40mm Stem Spacers |
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170mm | Monopost: 7.5, 40mm Stem Spacers |
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165mm | Monopost: 7, 40mm Stem Spacers |
Monopost: 8, 30mm Stem Spacers |
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160mm | Monopost: 6.5, 40mm Stem Spacers |
Monopost: 7.5, 30mm Stem Spacers |
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155mm | Monopost: 6, 40mm Stem Spacers |
Monopost: 7, 30mm Stem Spacers |
Monopost: 8, 20mm Stem Spacers |
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150mm | Monopost: 5.5, 40mm Stem Spacers |
Monopost: 6.5, 30mm Stem Spacers |
Monopost: 7.5, 20mm Stem Spacers |
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145mm | Monopost: 5, 40mm Stem Spacers |
Monopost: 6, 30mm Stem Spacers |
Monopost: 7, 20mm Stem Spacers |
Monopost: 8, 10mm Stem Spacers |
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140mm | Monopost: 4.5, 40mm Stem Spacers |
Monopost: 5.5, 30mm Stem Spacers |
Monopost: 6.5, 20mm Stem Spacers |
Monopost: 7.5, 10mm Stem Spacers |
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135mm | Monopost: 4, 40mm Stem Spacers |
Monopost: 5, 30mm Stem Spacers |
Monopost: 6, 20mm Stem Spacers |
Monopost: 7, 10mm Stem Spacers |
Monopost: 8, No Stem Spacers |
130mm | Monopost: 3.5, 40mm Stem Spacers |
Monopost: 4.5, 30mm Stem Spacers |
Monopost: 5.5, 20mm Stem Spacers |
Monopost: 6.5, 10mm Stem Spacers |
Monopost: 7.5, No Stem Spacers |
125mm | Monopost: 3, 40mm Stem Spacers |
Monopost: 4, 30mm Stem Spacers |
Monopost: 5, 20mm Stem Spacers |
Monopost: 6, 10mm Stem Spacers |
Monopost: 7, No Stem Spacers |
120mm | Monopost: 2.5, 40mm Stem Spacers |
Monopost: 3.5, 30mm Stem Spacers |
Monopost: 4.5, 20mm Stem Spacers |
Monopost: 5.5, 10mm Stem Spacers |
Monopost: 6.5, No Stem Spacers |
115mm | Monopost: 2, 40mm Stem Spacers |
Monopost: 3, 30mm Stem Spacers |
Monopost: 4, 20mm Stem Spacers |
Monopost: 5, 10mm Stem Spacers |
Monopost: 6, No Stem Spacers |
110mm | Monopost: 1.5, 40mm Stem Spacers |
Monopost: 2.5, 30mm Stem Spacers |
Monopost: 3.5, 20mm Stem Spacers |
Monopost: 4.5, 10mm Stem Spacers |
Monopost: 5.5, No Stem Spacers |
105mm | Monopost: 1, 40mm Stem Spacers |
Monopost: 2, 30mm Stem Spacers |
Monopost: 3, 20mm Stem Spacers |
Monopost: 4, 10mm Stem Spacers |
Monopost: 5, No Stem Spacers |
100mm | Monopost: 0.5, 40mm Stem Spacers |
Monopost: 1.5, 30mm Stem Spacers |
Monopost: 2.5, 20mm Stem Spacers |
Monopost: 3.5, 10mm Stem Spacers |
Monopost: 4.5, No Stem Spacers |
95mm | Monopost: 1, 30mm Stem Spacers |
Monopost: 2, 20mm Stem Spacers |
Monopost: 3, 10mm Stem Spacers |
Monopost: 4, No Stem Spacers |
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90mm | Monopost: 0.5, 30mm Stem Spacers |
Monopost: 1.5, 20mm Stem Spacers |
Monopost: 2.5, 10mm Stem Spacers |
Monopost: 3.5, No Stem Spacers |
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85mm | Monopost: 1, 20mm Stem Spacers |
Monopost: 2, 10mm Stem Spacers |
Monopost: 3, No Stem Spacers |
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80mm | Monopost: 0.5, 20mm Stem Spacers |
Monopost: 1.5, 10mm Stem Spacers |
Monopost: 2.5, No Stem Spacers |
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75mm | Monopost: 1, 10mm Stem Spacers |
Monopost: 2, No Stem Spacers |
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70mm | Monopost: 0.5, 10mm Stem Spacers |
Monopost: 1.5, No Stem Spacers |
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65mm | Monopost: 1, No Stem Spacers |
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60mm | Monopost: 0.5, No Stem Spacers |
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Pad Reach (BB to Pad Center) | |||||
Pads: +20mm » | 108mm | 111mm | 114mm | 117mm | 120mm |
Pads at Center » | 88mm | 91mm | 94mm | 97mm | 100mm |
Pads: -20mm » | 68mm | 71mm | 74mm | 77mm | 80mm |
All reach numbers above are measured to the center of the pad. Some fit systems measure to the back of the pad instead. Our Ergo Cups are 115mm long, so subtract 60mm from the reach numbers above for back-of-pad fit numbers.
Our Ergo Cups are much longer than many other arm cups on the market. Therefore, if the reach numbers above do not match your desired fit perfectly, small differences (10-20mm) may be negligible. |