Slack vs. Steep Head Tube Angle (my comparison & analysis)

This post compares the advantages and disadvantages of slack and steep head tube angles.


Head Tube Angle.

The head tube angle is formed by the head tube and the ground (or a horizontal line passing through the center of the bottom bracket. (image below)

What is a steep head tube angle?

The larger the head tube angle is, the steeper it is. For example, head tube angles around 71-73º or more are considered steep.

Steeper head tube angles are common for bicycles designed for efficient pedaling (e.g., road bikes, gravel bikes, urban commuters…etc.)

What is a slack head tube angle?

The smaller the head tube angle is, the slacker it is.

In general, angles under 70º are considered the beginning of the slack range. Slacker angles are common for mountain bikes designed to overcome massive obstacles during descents.

What Are The Advantages of Steeper Head Tube Angles

  • Speed

A steeper head tube angle positions the rider’s mass closer to the front wheel. Consequently, it becomes easier to assume a more aerodynamic position. Reduced drag equals greater average speed and efficiency.

For that reason, road and TT bikes do their best to minimize the drag created by the torso by making the rider’s back angle as horizontal as possible to the ground.

  • Climbing Power

Bicycles with steep head tube angles excel at climbing because the front wheel has better traction and there’s less mass over the rear end making it easier to spin the rear wheel.

As a result, the rider has an easier time maintaining a higher cadence. Cadence is a term indicating the rotations of the cranks per minute.

A higher cadence such as 90RPM or more produces a greater average speed and spares energy.

Also, the extra mass on the front wheel reduces the chances of accidental front wheel lifting when overcoming a section with a steep gradient.

If the front wheel goes up involuntarily, the rider loses control as well as the ability to maintain a steady pedaling output.

  • Technical Control as Slow Speeds

A steeper head tube angle makes tight turns at slow speeds easier. This is beneficial when the rider is covering technical terrain. For that reason, XC bikes have steeper head tube angles than trail models.

  • More Glute Involvement

The aerodynamic position resulting from the steeper HTA brings more of the rider’s hip extensors into the pedal stroke.

As a result, the rider can produce more power because the glutes are among the strongest muscles of the human body.

The Disadvantages of Steeper Head Tube Angles

  • Obstacles = Problem

The more aggressive an MTB is, the slacker its head tube angle becomes. This geometry makes it easier to overcome road irregularities.

When the head tube angle is slack, the front wheel is further in front of the rider and there’s less weight on it.

Consequently, the front wheel has an easier time rolling over obstacles. And if the front wheel overcomes an obstruction the chances that the rear wheel will follow are very high.

Steeper head tube angles have the opposite effect. The extra weight on the front end and the position of the front wheel closer to the rider’s mass make it more difficult to get over irregularities.

  • Falling Over The Handlebars

The steeper the head tube angle is, the easier it becomes to flip over the handlebars due to the extra mass on the front end.

  • Horizontal Back Angle

The horizontal back angle is beneficial from an aero standpoint, but it does stress the rider’s back more. If the bike fit is poor, and the rider isn’t fit enough for the riding volume, chronic pain may arise.

  • Wrist Stress

The shift towards the front end stresses the wrists, elbows, and shoulders because they have to support more of the rider’s weight.

The Advantages of Slack Head Tube Angles

Slack head tube angles weren’t a thing until MTBs acquired long travel suspension and became extremely aggressive downhill.

Until then, MTBs were essentially gravel bikes (although used on much harsher terrain) and had a very steep geometry.

The head tube angles of MTBs are getting slacker and slacker for the following reasons:

  • Stability Downhill

By putting the front wheel further in front of the rider, it becomes easier to ride fast downhill on off-road terrain because the front wheel has an easier time overcoming obstacles. Hence the extremely slack HTAs on downhill bikes.

  • Longer Travel Forks

A super slack head tube angle allows the user to run a fork with massive travel.

When the fork compresses, the head tube gets closer to the ground, and the head tube angle becomes steeper.

The slacker the starting head tube angle is, the more the fork can compress until it reaches its final position without putting the rider in danger.

Meanwhile, if you put such a fork on a regular bike with a steep head tube angle, the post-compression HTA will get dangerously sleep.

Also, the stress on the head tube itself will be massive, and sometimes the frame may crack (or completely disintegrate).

  • Harder To Flip Over The Handlebars

The slacker the HTA, the harder it is to get over the handlebars because the rider’s mass is closer to the rear wheel.

  • More Aggressive Front Braking

Thanks to the two points above, it’s possible to use the front brake slightly more aggressively. Of course, the extent of this technique depends on the rider’s skills, the terrain, the braking mechanism...etc.

  • Tricks Are Easier

Slacker head tube angles facilitate the lifting of the front wheel – an essential move for the performance of many tricks such as the bunny hops and rear wheel manual.

In the case of MTBs, lifting the front wheel is also used to overcome obstacles such as tree roots, rocks, small logs…etc.

The Disadvantages of Slack Head Tube Angles

  • Difficult Climbing

Slack head tube angles make climbing more difficult because the rear wheel is supporting more weight whereas the front wheel has less traction.

It’s also more difficult to exert force due to the body position of the rider. As a result, downhill bikes are rarely if ever used for climbing.

  • Slow Speed Steering = Weird

The slack HTA makes steering at slow speeds a bit uncomfortable and “boat-like”.

As a result, going around tight corners is difficult, especially uphill.

  • Turning Requires More Leaning In

Riders used to steeper head tube angles will find that steering via the bars only is not ideal when the HTA is extra slack.

The slacker the HTA is, the more the rider has to lean in the turns. Not everyone will like that.

  • Upright Position

Slack HTAs put the rider in a more upright position creating more drag.

Steeper Seat Tube Angles Come to Save The Day

The slacker the HTA, the steeper the seat tube angle becomes. This engineering aims to negate some of the downsides caused by the slack head tube angles.

A steeper seat tube angle places more of the rider’s weight towards the front wheel and thus allows more efficient pedaling and improves front wheel traction.

The Average Head Tube Angles Of Road Bikes

The table below contains the head tube angles of some popular road models.

Note: The data in the tables focuses on medium size frames.

Specialized Allez72.5º
Cannondale CAAD1373º
Giant Contend SL172.5º
Cervelo S573.5º
Giant Propel Advanced SL73º
Trek Madone73.5º
Tifosi Rostra72º
Boardman SLR 8.872.5º
Canyon Ultimate CF SLX73.3º
Mason Definition Chorus71.5º
Fara Cycling F/AR72º
Enigma Evoke MK373º
Reilly Fusion73º
Mason SLR SRAM Force70.5º
BMC Roadmachine 01 ONE72º
Cannondale SuperSix EVO Hi-MOD73º
Canyon Grail CF SLX 8 eTap72.8º
Cervelo Caledonia-5 Dura Ace72º
Mason Resolution EKAR71º
Merida Scultura Endurance Custom73º
Open MIN.D72.5º
Orbea Gain M20i72º
Rose Reveal Four DISC Ultegra Di272º
Scott Addict eRIDE Premium73.3º
Specialized S-Works Aethos73.5º
Storck Fascenario.3 Comp Disc Ultegra73.5º
Trek Domane+ LT 971.9º
Wilier Filante SLR71º
Road Bikes Head Tube Angle

Conclusion: Road bikes’ average head tube angle is 72.475º and is therefore on the steeper side.

The Average Head Tube Angles Of Gravel Bikes

The next table shows the average head tube angle of gravel bikes.

Canyon Grail CF SLX 8.0 Di272.5º
Canyon Grizl CF SL 8 1by72.5º
Giant Revolt Advanced Pro 071.5º
Trek Checkpoint SL6 eTap72.2º
Lauf Seigla Weekend Warrior72.5º
Vitus Venon EVO-GR Rival AXS 1x72.1º
Cannondale Topstone Carbon Rival AXS71.2º
Enve MOG71.25º
Specialized Diverge STR Expert71.75º
Boardman ADV 8.971.5º
Mason Bokeh Ti GRX Di271.5º
Reilly Gradient72º
Moots Routt 4571.5º
Marin Nicasio +72º
Cinelli  Nemo Gravel Disc Ekar Mendini71.5º
Ribble CGR 725 Steel72º

Conclusion: The average head tube angle of gravel bikes is 71.79º or about 1% slacker than what we observe on road bikes.

The ever so slightly slacker head tube angle isn’t surprising given that gravel bikes are designed to conquer light off-road terrain.

The Average Head Tube Angles Of Touring Bikes

The next table focuses on the head tube angles of popular touring bikes.

ModelHead Tube Angle
Salsa Marrakesh Sora70.8°
Trek 92071.3°
Trek 520 Disc 202071.8°
Giant ToughRoad SLR GX 1 Drop Bar70.5°
Kona Sutra70.5°
Bombtrack Arise Tour 202071°
Salsa VAYA GRX 60071.5°
Genesis Tour De Fer 3071°
Surly Disc Trucker72°
Salsa Marrakesh72.5°
Marin Four Corners71.5°
Masi Giramondo71°
Co-Motion Deschutes 202170.5°
Riverside Touring 90072°
Cube Travel71°
Rose Multisport 170°
Focus Atlas 6.7 EQP70.5°
Brodie Mega Tour 69°
Genesis Longitude68°
Panorama Taiga EXP69.7°
On-One Rocky Road70°
Touring Bikes

Conclusion: Touring bikes have a much slacker head tube angle than road and gravel bikes averaging at 70.77°

Why? The slacker head tube angle puts the rider in a more upright position which relieves wrist and back stress. The relaxed stance is especially beneficial over long distances.

The Average Head Tube Angles Of XC Bikes

The next table focuses on the head tube angles of popular XC bikes.

Lapierre Prorace CF 9.968º
Specialized Epic Pro67.5º
Vitus Rapide FS CRX67º
YT Izzo Uncaged 766.5º
BMC Fourstroke 01 Two AXS66.5º
Cannondale Scalpel HT Carbon 466.5º
Canyon Exceed CFR Team69º
Giant Anthem Advanced Pro 29 167.5º
Intense Sniper XC Expert67.5º
Merida Ninety-Six RC 900068.5º
Orbea Oiz M-Team67.9º
Pivot LES SL 29 Pro XT/XTR68.5º
Santa Cruz Blur C X01 AXS RSV68.3º
Scott Spark RC Team Issue AXS67.1º
Average: 67.5929º
XC Head Tube Angles

Conclusion: The angles of modern XC bikes are quite slack at 67.59º on average. Not a surprise since modern XC bikes have become way more aggressive than their ancestors.

The Average Head Tube Angles Of Trail Bikes

The next table focuses on trail bikes.

Bird Aether 965º
Boardman MTR 8.966º
Cannondale Habit 465.5º
Canyon Neuron 566º
Merida One-Forty 70065º
Propain Hugene Custom65.5º
Vitus Escarpe 29 CRS65º
Boardman MTR 9.066º
Canyon Spectral 125 CF 764º
Carrera Titan X67º
Focus JAM 8.965º
Kona Honzo ESD63º
Marin Rift Zone XR 27.565.6º
Polygon Siskiu T7 2965.5º
Privateer 141 SLX XT64.5º
Santa Cruz 5010 CC X01 RSV65.2º
Specialized Stumpjumper Comp63.5º-65.5º
Trek Fuel EX 8 Gen 663.5º-65.5º
Vitus Escarpe 29 CRX65º
YT Jeffsy Core 366.2º
Average: 65.1º
Trail Bikes Head Tube Angle

The Average Head Tube Angles Of Downhill Bikes

The next table contains the head tube angles of popular downhill bikes.

Canyon Sender CF 7.063º
Nukeproof Dissent 290 Comp63º
Saracen Myst AL63º
Scott Gambler 900 Tuned62.9º
Vitus Dominer63º
Commencal Supreme DH62.2º
YT Industries Tues63.5°
Atherton Bikes DH Prototype63°
Mondraker Summum63.5º
Specialized Demo 2963.2º
Polygon Xquarone DH63º
Santa Cruz V1063.7°
Saracen Myst63°
Scott Gambler63.9º
Downhill Bikes HeadTube Angle

Conclusion: Unsurprisingly, downhill bikes have the slackest head tube angle on average at 63.09º.

The Average Head Tube Angles Of Dirt Jump Bikes

The next table focuses on the head tube angle of dirt jumpers.

Airdrop Fade69°
Saracen Amplitude CR268.5°
Santa Cruz Jackal68.7°
NS Bikes Metropolis 370°
DMR Sect69°
Commencal Absolut72°
Scott Voltage YZ 0.168.5°
Marin Alcatraz69°
Canyon Stitched 72068.5°
NS Bikes Movement 369°
NS Bikes Zircus70°
Haro Steel Reserve 1.169°
Polygon TRID 202170°
Dirt Jumpers Head Tube Angle

Conclusion: Dirt jumpers have a conservative head tube angle of around 69° that’s neither steep nor as slack as what we observe on aggressive MTBs.

The Average Head Tube Angles Of Race BMX Models

The next table analyzes the head tube angles of RACE BMXs.

ModelHead Tube Angle
BMX Race Chase Edge Pro XL73°
Haro Blackout74°
Haro Pro 2473.3°
Haro Pro XL74°
Haro Expert73°
Chase Edge Expert BMX72°
Chase Element Pro74°
Cobalt Junior73°
Xenon Expert73.5°
Quartz PRO73°
Helium Cruiser71°
Redline 2022 Proline74°
DK Sprinter74°
Redline MX Expert XL73°
Race BMX Head Tube Angles

Conclusion: Race BMX bikes have steep head tube angles averaging 73.2°

The Average Head Tube Angles Of Freestyle BMX Models

The next table presents the seat tube angles of freestyle BMX bikes.

ModelSeat Tube Angle
Mongoose Legion L10075°
Sunday Street Sweeper Pro 75.25°
Fueler 2274.75°
Performer 20.5 Mercado75°
CK PRO75.5°
CK AM75.5°
SD AM75°
Haro Hoover75.5°
La Bastille75.5°
Haro Quist75°
Mid City75°
Downtown 2074.5°
Average: 75.115°
Freestyle BMX HeadTube Angle

Conclusion: Freestyle BMX bikes have very steep head tube angles averaging at about 75°. The goal in this case is to increase the responsiveness of the bike – a critical property when performing technical stunts.

Meanwhile, race BMX bikes do not have to be as technical and thus can get away with slightly slacker head tube angles (values above) making it easier to overcome obstacles in front of the rider.

The list below contains the average head tube angles in the tables going from the steepest to the slackest.

BMX (freestyle)75.1°
BMX (race)73.2°
Road Bikes72.47º
Gravel Bikes71.79º
Touring Bikes70.77º
Dirt Jumpers69.3º

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