The importance of stack and reach in your bike's geometry

What are stack and reach on a bicycle?

Definition of stack

The stack represents the frame height. It is the vertical distance between the bottom bracket axle and the superior top of the head tube. The higher the stack, the more upright and comfortable the rider's position will be. On the other hand, a low stack means a more aerodynamic and sporty posture.

Definition of reach

The reach measures the horizontal reach: the distance between the bottom bracket axle and the superior center of the head tube, but on a horizontal line. This value determines how much the rider stretches out on the bike. A long reach favors stability and performance at high speed; a short one provides greater control and comfort.

How they are measured on the frame

Both stack and reach are measured in millimeters. Manufacturers include them in the geometry tables of each model.

• Stack: vertical line from the center of the bottom bracket axle to the superior top of the head tube.
  
  

• Reach: horizontal line from the same point at the bottom bracket axle to the vertical of the head tube.
  
  

Differences between MTB, road and gravel

• Road: aims for a long reach and low stack for a more aggressive position.
  
  

• MTB: prioritizes control and stability; therefore, it usually has high stack and long reach.
  
  

• Gravel: seeks an intermediate balance between comfort and performance.
  
  

Why are stack and reach important?

Impact on rider posture

These two values determine how you sit and move on the bike.

• A high stack puts you more upright, reducing tension in the neck and back.
  
  

• A long reach forces you to stretch out more, ideal for sporty or aerodynamic positions.
  
  

Influence on control and stability

The reach directly affects the length of the front triangle of the frame. A greater reach provides more stability on descents, while a shorter one improves maneuverability in technical sections.

Relationship with performance and comfort

The correct stack and reach balance efficiency, comfort, and control. In summary:

• Too much reach: forced position and fatigue.
  
  

• Little reach or too much stack: comfortable posture, but less efficient in performance.
  
  

How these values define the geometry of the bicycle

In reality, stack and reach are the pillars of modern geometry. Beyond generic sizes (S, M, L), they are what define how a bike behaves and feels when pedaling.

How to calculate the stack and reach of your bicycle

Measurement methods

You can calculate them yourself if you know the frame:

1. Place the bike on a flat surface.
   
   

2. Measure vertically from the bottom bracket to the top superior of the head tube (stack).
   
   

3. Then measure horizontally from the bottom bracket to the vertical of the head tube (reach).
   
   

Online tools and manufacturer tables

The easiest way is to consult the manufacturer's technical sheet. There are also online calculators (like Bike Insights or Geometry Geeks) that automatically compare models and sizes.

Practical calculation example

Suppose a bicycle has:

• Stack: 600 mm
  
  

• Reach: 420 mm
  This indicates a balanced geometry, comfortable and with good stability. An aero road bike, on the other hand, may have stack 540 mm and reach 400 mm, offering a lower and faster position.
  
  

How to choose the right size according to stack and reach

Interpreting the values on road bikes

Look for a balance between aerodynamics and comfort. If you do long rides or bike touring, prioritize a higher stack. If you race or train hard, a lower stack and longer reach will give you better performance.

Interpreting the values on MTB bikes

In mountain biking, a long reach and medium/high stack provide control and stability. That's why modern MTBs are “longer and lower” than those from years ago.

Stack and reach according to rider height

• Tall riders usually feel comfortable with a longer reach.
  
  

• Short riders prefer shorter stack and reach to maintain control.
  
  

When to prioritize stack and when to prioritize reach

• If you want comfort and long rides, prioritize stack.
  
  

• If you want performance and precise handling, prioritize reach.
  
  

Geometry differences according to the type of bike

How do I know if my bike has too much reach or too little stack?

If you feel too stretched out, your bike probably has a long reach. If you feel the handlebar is very high, it may have a tall stack.

Is a bike with a high or low stack better?

It depends on your goal: a high stack gives more comfort, a low one favors aerodynamics.

Does reach influence the bike size?

Yes. In fact, many experts recommend choosing the size based on reach, since it is the value that most affects the riding position.

Can I modify stack and reach by adjusting the handlebar or stem?

Yes, but with limits. Changing the stem or the spacers under the handlebar can slightly adjust the position, although it does not replace an incorrect geometry.

Important information before buying a bicycle

The stack and reach are much more than simple measurements: they are the values that define the ergonomics, control, and performance of your bicycle.

Understanding them will help you to:

• Choose the ideal size.
  
  

• Adjust the correct posture.
  
  

• Improve your comfort and efficiency on the bike.
  
  

If you are looking for a new bicycle and want to get the perfect geometry, at Tuvalum you will find certified bicycles adjusted by experts, so you can ride with the ideal balance between comfort and performance.