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Gravel bikes have a very conservative seat tube angle of about 73.5° because they have to be versatile “climbers” and “descenders”.

Therefore, extreme geometrical choices are not an option if performance and comfort are the goals.

The table below contains the seat tube angles of popular gravel bikes. If you are not familiar with the terms effective seat tube angle and actual seat tube angle, you can read this post.

Conclusion: The average seat tube angle of gravel bikes is 73.3°. This is a conservative number that could not be classified as steep or slack. It’s balanced right in the middle and matches the values that we see on standard road bikes.

Why Don’t Gravel Bikes Have a Steeper or a Slacker Seat Tube Angle?

The geometry of a bicycle frame always follows function. Gravel bikes aren’t an exception. The 73.3° angle is chosen for the following reasons:

• Gravel bikes are both climbers and descenders

Gravel bikes are designed for both ascending and descending. As universal machines, they cannot afford to have extreme values in their geometry because one of the functions will suffer. Thus, staying in the middle makes the most sense.

In general, a slacker head tube angle + a slacker seat tube angle is a good combination only when the bike is designed solely for descending. This is one of the reasons behind the geometry of downhill bikes.

However, that geometry makes climbing and even pedaling on flat roads highly inefficient and is therefore absent on universal bicycles.

If the seat tube angle of gravel bikes is steeper, the climbing capabilities of the bike could improve thanks to the extra front wheel traction. However, an extremely steep seat tube angle would have the following negative properties:

• Too much weight on the front wheel increases the chance of flipping over the handlebars.

• The back of the rider will become more upright unless the saddle-to-handlebar drop is increased dramatically. A more vertical back angle would reduce the involvement of the hip extensors (glutes) while increasing the role of the quadriceps.

(More quads in the pedal stroke is not bad in and of itself, but sometimes the extra stress results in knee pain, especially when covering long distances.)

• Extra Drag (The more upright the rider is, the more body drag there is.)

• Extra stress on the wrists, elbows, and shoulders because they have to support more weight.

• Shorter effective top tube (potentially) making the rider feel “compressed”.

FAQ: What about a normal head tube angle + a slack seat tube angle?

An overly slack seat tube angle has its positive effects (more glute involvement, less knee stress…etc.), but it hurts the climbing abilities of a bicycle by placing more weight on the rear wheel and reducing the traction of the front end.

The more weight there is on the rear, the harder it becomes to spin the wheel, especially when conquering a hill. The weight shift to the rear may also cause accidental lifts of the front wheel making it difficult to conquer technical terrain.

Don’t Obsess Over The Seat Tube Angle Of Your Gravel Bike

Bicycle geometry is a fairly complex subject and requires focus on multiple variables – not just one. In other words, the overall geometry of a bicycle is more important than one single angle even though all angles are connected.

Ultimately, there are parameters that hold a higher priority than the seat tube angle. Those would be:

• Frame Size (The angles don’t matter when the frame is too small or too big.)
• Bike Weight (The lighter the bike, the easier it is to climb with it.)
• Gear Range (If the gears are too high for the terrain, all other parameters become irrelevant.)
• Frame Quality
• Wheel Quality
• Training (Let’s be honest. It doesn’t matter what your bike is when you don’t train enough.)

Don’t forget that you can affect the effective seat tube angle via the saddle.

Summary: What You Need To Know

• Gravel bikes have a conservative seat tube angle of about 73.5° because they are good at descending and ascending all while offering long-distance comfort.

• If the angle gets too steep, the chances of getting over the handlebars increase and there’s more drag. In some cases, the rider may also experience some knee pain.

• If the angle is too slack, the climbing properties of the bike are hurt because there’s extra weight on the rear wheel and diminished front-end traction.

• Focus on the overall qualities of the bike rather than just the seat tube angle if your goal is balanced performance.