Tech Talk: The importance of stack and reach

The best way to tinker with geometry on your current bike

Components Tech
Adjusting stack and reach is one of the best ways to tinker with geometry on your bike. Photo courtesy of Art’s Cyclery

Adjusting stack and reach is one of the best ways to tinker with geometry on your bike (click to enlarge). Photo courtesy of Art’s Cyclery

Editors Note: This article was written by Art’s Cyclery web content editor Brett Murphy, who uses his mechanical engineering background to explain the latest industry advances and breakdown component design. The original post can be found here.

Previously, we discussed the relationships between wheelbase, headtube angle, and BB height, and talked about how they affect handling and compared some different purpose-built rigs. Now it’s time to look at stack and reach measurements, and illustrate the best ways to tinker with geometry on your current bike.

An added element of complexity with mountain geometry comes from the complex frame designs. Top tube lengths can be difficult to measure due to sloping tubes, creating the need for effective top tube (ETT) measurements in geometry specifications. Effective top tube measures as the horizontal distance from the intersection of the seat tube and top tube, to the intersection of the head tube and top tube.

While this solved part of the problem with representing geometries, frames can still vary greatly without changing effective top tube. For example, two bikes with the same reach can have different effective top tube lengths. This is accomplished by decreasing seat tube angle, pushing the saddle back, increasing the distance to the handlebars, while the ETT remains the same.

These are the critical dimensions that make up a frame’s geometry. Photo courtesy of Art’s Cyclery

These are the critical dimensions that make up a frame’s geometry (click to enlarge). Photo courtesy of Art’s Cyclery

Reach and stack measure the horizontal and vertical distances from the bottom bracket to the top of the head tube respectively. The purpose of these measurements is to establish a standard of comparison for fit across all brands. Similar reach and stack measurements between bikes will help to match the contact point engagement. These two measurements can be the same across multiple bikes, however, the wheelbase, steering characteristics, and numerous other factors can change underneath you. So while reach and stack will help you find a properly sized bicycle, you will still need to evaluate other geometries to arrive at the ride you’re looking for.

Continue to page 2 for more about stack and reach »

About the author: Arts Cyclery

This article was originally published on the Art's Cyclery Blog. Art's Cyclery is dedicated to offering free expert advice, how-to videos, and in-depth product reviews on ArtsCyclery.com to help riders make an educated decision when selecting cycling gear.


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  • HDL says:

    in the article it states ” So while reach and stack will help you find a properly sized bicycle, you will still need to evaluate other geometries to arrive at the ride you’re looking for”. But never says how reach and stack help you find a properly sized bicycle. I have looked for this information and cannot find it anywhere. Can anyone chime in? Are there measurements to do on my body to figure out what reach and stack I should be looking for?

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