Ultra-fast answer: A 75° seat tube angle is too steep for a road, gravel, downhill, or a touring bike, but it can work just fine for an XC or a trail model.
A 75-degree seat tube angle can also be found on some urban bikes with a very upward geometry.
Note: If you are unfamiliar with the terms effective seat tube angle and actual seat tube angle, you can find their definitions in this post.
Modern MTBs Have Slack Head Tube Angles and Steep Seat Tube Angles
The reason why a 75° seat tube angle isn’t too steep for some MTBs is that the modern frames come with a slack head tube angle that necessitates steeping of the seat tube angle.
The head tube angle (HTA) is the angle between the head tube and the ground. A slacker or smaller head tube angle positions the front wheel further in front of the rider.
The advantages of a slacker HTA are:
- Safer descents
A slacker head tube angle makes it easier for the front end to overcome obstacles and positions the rider further behind the front wheel. Consequently, the risk of getting over the handlebars is reduced.
- Easier front-wheel lifts
A slacker head tube angle reduces the weight on the front and makes it easier to lift the front wheel. This is beneficial when the rider wants to pass through a large obstacle or perform a trick such as the bunny hop.
- Compatibility with long-travel forks
A slacker head tube angle “agrees” with the modern long-travel forks.
However, a slacker head tube angle has downsides too. It puts too much weight on the rear wheel and hurts maneuverability at slow speeds. It also makes pedaling inefficient because the rider’s center of gravity is too far beyond the bottom bracket.
To fight this effect, modern MTBs combine a slack head tube angle with a steep seat tube angle.
The steeper seat tube angle cancels out the aforementioned negative effects by putting the rider closer to the front wheel. The position “relieves” the rear wheel and improves pedaling efficiency because the mass center is once again above the bottom bracket.
In other words, the modern steep seat tube angles are the result of slacker head tube angles rather than an independent goal.
So, when is a 75-degree seat tube angle acceptable?
However, it’s found among XC and Enduro models.
The table below contains the seat tube angles of popular XC bikes.
|Model||Seat Tube Angle|
|Lapierre Prorace CF 9.9||73.7°|
|Specialized Epic Pro||74.75°|
|Vitus Rapide FS CRX||77°|
|YT Izzo Uncaged 7||77.5°|
|BMC Fourstroke 01 Two AXS||75.6°|
|Cannondale Scalpel HT Carbon 4||74.5°|
|Canyon Exceed CFR Team||75°|
|Giant Anthem Advanced Pro 29 1||75.5°|
|Intense Sniper XC Expert||74°|
|Merida Ninety-Six RC 9000||76.5°|
|Orbea Oiz M-Team||74°|
|Pivot LES SL 29 Pro XT/XTR||74.5°|
|Santa Cruz Blur C X01 AXS RSV||74°|
|Scott Spark RC Team Issue AXS||76.1°|
Conclusion: The average angle of modern XC bikes is about 75°. That said, some less aggressive models have a steeper head tube angle and consequently a slacker seat tube angle.
|Model||Seat Tube Angle|
|Deviate Claymore 2022||78°|
|Intense Tracer 279 S||77.4°|
|Merida ONE-SIXTY 8000||79°|
|Mondraker Carbon Foxy RR||76°|
|Santa Cruz Megatower X01 AXS RSV||77.4°|
|SIMPLON Rapcon 170/165||79°|
|Specialized Stumpjumper EVO Elite Alloy||78°|
|Yeti 160E T1||78°|
|Yeti SB160 T3||77.5°|
Conclusion: The average seat tube angle of modern enduro bikes is very steep at around 77.78°.
By those standards, a 75° seat tube angle is actually too slack.
Summary: What You Need To Know
- А 75° degree seat tube angle is too steep for road, gravel, touring, and downhill bikes, but it’s acceptable for XC bikes and some trail machines.
- By modern enduro standards, a 75° seat tube angle is somewhat too slack.