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A hardtail can be used as a dirt jumper only if it has an aggressive geometry already resembling that of a dirt jump bike. Otherwise, the hardtail will make the execution of some tricks difficult and of others impossible.

Hardtail vs. Dirt Jumper Geometry

The list below contains the geometrical differences between hardtails and dirt jumpers:

• Frame Size

Hardtail MTBs are designed for comfortable pedaling and come in different sizes to suit riders of all heights. In different, most dirt jumpers are unisize.

The main reason why dirt jumpers use smaller frames is that they’re engineered for street riding done out of the saddle. The smaller the bike, the easier it is to throw it around.

And since dirt jumpers aren’t designed for long distances, the fact that the frame is too small for comfortable pedaling isn’t detrimental.

If you try to use a large hardtail as a dirt jumper, it will be a lot more difficult to perform certain tricks due to the size of the bike.

• Slack vs. Steep Head Tube Angle

The head tube angle (HTA) is the angle between the head tube of the bike and the ground.

Modern hardtails have a slack headtube angle (e.g., 64-degrees). Meanwhile, dirt jumpers have a much steeper HTA – around 67-degrees.

Hardtails rely on a slacker head tube angle because it pushes the wheel further away from the rider and makes it easier to ride over diverse terrain.

However, the slack head tube angle hurts maneuverability at slow speeds which is crucial for street riding. Hence why some tricks are more difficult to perform on a hardtail.

The table below compares the head tube angles of dirt jumpers and hardtails:

Conclusion: On average, the head tube angle of dirt jumpers is 2-3° steeper than that of modern hardtails. This makes dirt jumpers more nimble at slow speed.

• Short chainstays

Dirt jumpers have shorter chainstays which facilitate the execution of the tricks such as manuals and bunny hops.

However, shorter chainstays reduce the wheelbase of the bike and decrease the overall stability when riding at speed. Hence why regular hardtails have longer chainstays which increase the bike’s stability but make the execution of technical stunts more difficult. This is one of the reasons why hardtails are harder to manual and bunny hop.

The table below compares the chainstay length of dirt jumpers and hardtails:

Conclusion: On average, the chainstays of dirt jumpers are 41mm shorter. This is a substantial difference that heavily alters the bike’s behavior. To learn more about the effect of shorter chainstays, consider reading this article.

• Bottom Bracket Drop

The bottom bracket drop is the vertical distance between the center of the bottom bracket and an imaginary horizontal line between the front and rear axles.

Dirt jumpers tend to have a significantly shorter bottom bracket drop than hardtails.

The motive behind the engineering is found once again in the purpose of the bike – a small bottom bracket drop makes the bike better suited for manuals and hops whereas a big bottom bracket drop increases stability.

Different Front Suspension

The forks on hardtails and dirt jumpers may appear identical, but there are notable differences between the two.

The forks on modern hardtails have lots of travel sometimes reaching 160mm. This makes hardtails great for riding on terrain with lots of obstacles. Also, hardtail suspension is somewhat softer, at least when it comes with factory settings because it’s meant to absorb lots of small irregularities.

Conversely, the suspension of dirt jumpers has less travel (100-120mm) and is often firmer because it’s designed to absorb massive landings rather than to smoothen one’s ride over rocks.

Furthermore, many street riders prefer to have a firmer suspension because it’s closer to a rigid fork. This quality makes the suspension of dirt jumpers more responsive and predictable which is good for tricks.

That said, there are also hardtail forks that can be made to behave as needed for dirt jumping – the travel can be reduced and the softness of the fork can be regulated by putting more air in it (if the fork is air-based, of course).

26″ vs. 27.5″ and 29″ Tires

Dirt jumpers use 24″ and 26″ wheels with 26″ being the most common wheel size.

26″ wheels are not chosen because dirt jumpers are living in the past, but because they provide key benefits such as:

• Maneuverability

The smaller the wheel, the more maneuverable it is. It would be absurd to equip a dirt jumper with 29″ wheels.

• Faster Acceleration

Smaller wheels accelerate faster than wheels with a larger circumference. This is beneficial for street riding because very often the rider doesn’t have a lot of room to accelerate before a trick.

• Strength

All things being equal, a smaller wheel is a stronger wheel because the rim acts as a shorter lever against the spokes during a landing. Also, the shorter spokes make the wheel stiffer and more stress-resistant. A 26″ wheel of good quality is quite likely to outlive its 29″ version.

• Small

The smaller profile of 26″ wheels contributes to the overall compactness of a dirt jumper which in return facilitates the execution of tricks.

In different, hardtails use either 27.5″ or 29″ wheels.

The advantage of those wheel sizes is that they have a greater roll-over ability. Or in other words, they have an easier time rolling over obstacles. This property makes the bike faster on a trail but hurts its maneuverability.

Some people may wonder whether it’s possible to install a 26″ wheel on a regular hardtail.

You can find the dedicated articles on the topic below:

26″ Wheels On a 27.5″ Bike

29″ Wheels On a 29″ Bike

Multi-Purpose Hardtails

While the average hardtail isn’t suited for dirt jumping because it’s either too XC or trail-oriented, some models represent a mix between a hardtail and a dirt jumper.

Those bikes are MTBs with a geometry facilitating the performance of some dirt jump tricks. If you possess one of those models, the bike can be used as a substitute for a dirt jumper, at least during the initial learning phase. But as the rider get’s more advanced and hungrier, a dedicated dirt jumper would help.

Example models:

• NS Clash
• Kona Shred
• Dartmoor Shine
• Santa Cruz Chameleon
• Chromag Stylus
• Dartmoor Hornet
• NS Eccentric
• Marin San Quentin
• …etc.

Summary: What You Need to Know

Hardtails are not optimal for dirt jumping because:

• Large size (harder to throw the bike around)
• Long chainstays (hops and manuals are more difficult)
• Slack head tube angle (poor maneuverability at slow speed)
• Large wheels (weaker, extra heavy, and less maneuverable)
• Front suspension with massive travel

That said, there are dirt jumpers that are designed to be multi-purpose bikes and fall in a territory between a dirt jumper and a hardtail. They can be used for both disciplines.