Reach and Stack have become the benchmark for evaluating whether a bike or frame is the right size for us. These measurements have their pros and cons. But above all, they weren’t originally intended to measure a road bike; instead, they were brought from the gravity world to more pedaled disciplines. The real question is: are these measurements really the best way to assess if a bike is suitable for us? Let’s analyze it together.
Why and Purpose of Reach and Stack
Reach and Stack, as mentioned, were devised to evaluate the measurements of frames in the Gravity world, such as Downhill bikes, Enduro bikes, but also BMX or Bike Trial. In these disciplines, Reach and Stack solve a fundamental problem: measuring and evaluating a bike frame with only two points of contact. The points of contact are where our body connects with the bike. In pedaled disciplines, the most important point of contact is the saddle, followed by the handlebar and pedals. In Gravity disciplines, the saddle is not used or entirely absent, as in Bike Trials. The introduction of these measurements was therefore a fundamental breakthrough for cyclists whose primary need was evaluating the handlebar height with powerful shock-absorbing forks or who needed to assess the bike’s length without the reference point of the saddle.
The Transition to Pedaled Disciplines
By ‘pedaled disciplines,’ we mean Road Biking, Gravel/Cyclocross, Track, but also Cross-Country Mountain Biking. Reach and Stack quickly made their way into this type of cycling, initially as complementary measures. The more measurements we have, the more precise we can be in transferring geometries and position from one bike to another or from the biomechanic’s ergometer to the bike set up on the road.
However, some have become enamored with Reach and Stack to the extent of theorizing that all other measurements are superfluous, and these two measures alone are sufficient for evaluating a bike’s size. As a frame manufacturing company, we often receive emails from individuals who only provide these two measurements, asking for a customized frame. But this is limiting in the world of pedaled cycling, where we have three points of contact with the bike, and where contact with the saddle remains the fundamental and most important among the three points of contact with the bike.
Reach and Stack, what are they?
Let’s take a step back and explain to those who might not have a clear understanding of the measurements we’re discussing. Essentially, Reach refers to the horizontal distance between the center of the bike’s bottom bracket and a vertical line passing through the top of the head tube. This data can provide an indication of the frame’s length from the bottom bracket to the handlebar, excluding the saddle’s influence. Stack, on the other hand, indicates the height from the center of the bottom bracket to where the horizontal line crosses the head tube, offering an idea of the bike’s height and the rider’s position concerning the ground.
You’ll understand how these measurements revolutionized the system in the world of gravity bikes, where the saddle is either absent or has little significance because most performance is achieved while standing on the pedals. However, it’s equally easy to understand that the Stack of a pedaled bike essentially equates to the height of the head tube because when comparing two bikes of the same discipline with rigid forks, we’ll have the same fork crown height. Reach, on the other hand, provides a bike’s length without considering our seated position, thus having a considerable margin of error.
Measuring at Home
To obtain these measurements without an ergometer or laser tools for accurate distance measurement, simply lean your bike against a wall as vertically as possible. Measure the distance from the ground to the top of the head tube’s center and then from the center of the bottom bracket to the ground. The difference will be the Stack.
By positioning the bike vertically but with the rear wheel against a wall, measure the distance from the center of the top of the head tube to the wall, and from the center of the bottom bracket to the wall. The difference will be the Reach.
Variations of Reach and Stack
These measurements aren’t singular. Over time, variations have emerged from the original measurements based on the two reference points at the bottom bracket and the center of the top of the head tube. One variant includes measuring at the center of the handlebar, replacing the measurement at the head tube’s center, thereby incorporating the stem’s angle. A third and less commonly used variant considers the bottom bracket center and the brake lever positions.
Are these measurements interchangeable?
Absolutely. As previously mentioned, within the same discipline and staying within pedaled cycling, we’ll have forks of identical or very similar heights. Therefore, the head tube’s height equates to Stack, with the head tube being much easier and more immediate to measure. Concerning the bike’s length, finding the virtual length of the frame produces a more accurate result than Reach, which doesn’t include the saddle’s influence.
Are these measurements reliable?
Yes and no. They are absolutely reliable for Gravity bikes. They are accurate for more pedaled cycling bikes as well – a slight change in the head angle can vary Reach and Stack by 2-3 millimeters, which is an acceptable margin of error. However, they don’t provide an exact interpretation of the bike because they don’t involve the fundamental point of contact: the saddle. Connected to the saddle is the seat tube. A different seat tube angle can completely alter the bike’s character. We might find two bikes with the same Reach and Stack, one designed for intense racing and competition, while the other is suitable for long distances. Moreover, by not considering the saddle, they overlook crucial anthropometric measurements, such as femur length or pelvic rotation.
Is evaluating a bike’s size based solely on Reach and Stack correct?
Yes, if it’s for Gravity disciplines. No, if it’s for pedaled disciplines. In a frame’s geometry, around 40 different measurements are considered, and reducing them to 2 inevitably overlooks important data. Moreover, the most crucial measurement on a bike is the relationship between the saddle and the bottom bracket – both the distance from it (saddle height) and the angle (saddle setback). This measurement significantly impacts our position on the bike, and Reach and Stack do not account for this data.