Is a 73 Degree Seat Tube Angle Too Slack (fast answer + a comparison chart)

Condensed Answer:

A 73° seat tube angle is 1° to 4° slacker than what we find on modern MTBs. In the world of road bikes, 73° is a common middle ground.

What is a seat tube angle?

Many assume that the seat tube angle is formed by the seat tube and the chainstaysbut this isn’t correct.

The seat tube angle (STA) is the angle between the seat tube and a horizontal line (parallel to the ground) running through the bottom bracket.

What is a Slack Seat Tube Angle?

The smaller the STA, the “slacker it is”.

In different, if the angle gets larger, it is considered “steeper”.

Why Do Modern MTBs Have Steeper Seat Tube Angles?

The main reason for the steeper tube angles on modern MTBs is actually another angle part of the frame geometry – namely the Head Tube Angle or HTA.

The HTA is the angle formed by the head tube and the ground.

Modern MTBs have slacker (smaller) HTAs in comparison to the MTBs of the past. The advantages of a slacker HTA are:

  • The front wheel is positioned further in front of the frame and has an easier time overcoming obstacles.
  • The frame can be combined with a long fork with a massive travel.
  • The rider is less likely to go over the handlebars. In other words, slacker HTAs are safer when going downhill.

The slacker head tube angles of modern MTBs require steeper seat tube angles for balance.

If the HTA of an MTB frame is slackened and the STA remains the same, the rider will be too far back.

As a result, climbing will be more difficult, and the chances of lifting the front end of the bike accidentally will be high.

Ultimately, the steeper seat tube angles today are simply a necessity resulting from the slacker head tube angles rather than a goal.

So, Is a 73 Degree Seat Tube Angle Too Slack?

To answer the question, it’s necessary to examine the STAs of modern XC and trail bikes.

Specialized Epic World Cup PRO74.5°
Cannondale Scalpel HT Hi-MOD Ultimate Carbon74.5°
FOCUS Raven 8.874°
Specialized Chisel Comp74°
Specialized Epic Expert75.8°
Santa Cruz Highball 3.073°
Scott Spark 93075.9°
Santa Cruz Blur CC X0176.3°
YT Izzo Pro Race77°
Merida Ninety-Six RC900074.5°
Giant Anthem Advanced Pro75.5°
BMC Fourstroke 01 One75.6°
Trek Supercaliber 9.874°
Giant XTC SLR74°
Average: 74.9°
XC bikes and modern STAs
Canyon Spectral CF 7.076°
Focus JAM 6.8 Nine76°
Giant Trance 29 276.3° 
Merida ONE-FORTY 80075°
Scott Genius 95075.3°
Stumpjumper Comp Alloy77.7°
Trek Remedy 874.7°
YT Jeffsy 27 AL Base75°
Cannondale Habit Carbon 177.5°
Nukeproof Reactor 29075.5°
Norco Optic C176°
Trail bikes and Modern STA


  • The average seat tube angle of modern XC bikes is 74.9°.
  • The average seat tube angle of trail bikes is 75.9°.

Given the data, a 73° seat tube angle is indeed too slack by modern standards.

That being said, the seat tube angle is just one part of the equation and should never be studied in isolation.

There are other factors that hold a higher importance. Those would be:

  • Frame quality (it’s better to have a well-built bike with “too slack” STA than an optimal STA and a badly built frame).
  • Wheels
  • Overall comfort (Angles don’t matter when you feel weird and uncomfortable on your bike).

Mini Summary: What You Need To Know

  • Modern MTBs have slacker head tube angles which demand steeper seat tube angles for optimal balance and performance.
  • A 73° is technically too slack by modern standards, but it’s not outdated to the point where the bike can’t serve you well.
  • If the bike feels good and is built well, then 2-3 degrees don’t matter. Just ride.

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