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Dirt jumpers aren’t optimal for trail riding but can be used for that purpose if the rider is willing to compromise and doesn’t expect top performance and comfort.

What Is a Dirt Jump Bike?

Dirt jumpers are 24 or 26-inch hardtail bikes optimized for skate park riding and jumping.

They’re a mix between a BMX and a mountain bike and work well for tricks and acrobatic jumps.

The Differences Between Dirt Jump Bikes and Hardtail Mountain Bikes

On the surface, a dirt jumper looks like a hardtail MTB. And while there are many similarities between the two, there are also major differences strongly influencing the type of riding that one can do on both machines.

Geometry

Head Tube Angle

The head tube angle (HTA) of a bicycle frame is fundamental to a bike’s behavior.

There are two types of head angles – slack and steep.

А slack head tube angle puts the front wheel further away from the bike whereas a steep head angle positions the front wheel closer to the rider.

The frames of dirt jumpers are compact and come with a steep head angle (e.g., 69°) by the standards of modern MTBs.

The steep head angle increases the maneuverability of the bike, especially at low speeds and keeps the rider’s weight closer to the front wheel.

In consequence, it becomes easier to lift the front wheel – a desirable trait for stunt bikes.

In different, modern hardtails have a much slacker head angle (e.g., 66.5°).

The table below contains the head tube angles of popular hardtails and dirt jumpers.

Head Тube Angle Comparison

Findings: The average head tube angle of the hardtails in the list is 0.88° slacker than the average head tube angle of the dirt jumpers.

The benefits of a slacker head tube angle are:

1. More stability during descents

2. Lower chances of flipping over the bars due to the increased wheelbase (distance between the front and rear axle)

3. An opportunity to run a fork with greater travel.

When a suspension fork compresses, the head tube angle of the bike gets steeper.

Thus, bikes with a steep head tube angle cannot safely run forks with lots of travel because the head tube angle will get dangerously steep upon compression.

Ultimately, a dirt jumper is not as safe to ride downhill as a modern hardtail due to the steeper geometry.

Seat Tube Length

Dirt jumpers have very short seat tubes in order to keep the frame compact and get the seat out of the way during tricks. This is one of the reasons why a classic dirt jumper is an awful climber.

Strong riders may be able to cover long-distances riding out of the saddle, but sooner or later fatigue will catch to anyone because the position is uncomfortable, highly inefficient (anti-aero) and tiring.

A hardtail, on the other hand, is a much better climber and long distance bike because the seat tube is longer and allows you to pedal with greater efficiency and comfort.

This point alone is a strong reason not to use a dedicated dirt jumper as a trail bike.

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

As you can see, the seat tubes of dirt jumpers are much shorter than those of hardtail MTBs.

Seat Tube Angle

A slack seat tube angle puts the rider closer to the rear wheel whereas a steep one positions the rider forward.

Trail bikes are moving towards steeper seat tube angles which are the only way to compensate for the slack head tube geometry.

Dirt jumpers have no choice but to have slacker seat tube angles. Otherwise, the rider would be too “squished”.

As a result, when you put a long seat post on a dirt jumper, the seat often ends up significantly behind the bottom bracket. This makes pedaling inefficient and uncomfortable.

The table below contains the seat tube angles of popular hardtails and dirt jumpers.

*The seat tube angles of hardtails vary according to the size of the frame.

Findings: The average seat tube angle of the hardtails in the list is 1.77° steeper than that of the dirt jumpers.

Chainstays

To facilitate the performance of tricks such as bunny hops and manuals, dirt jumpers have significantly shorter chainstays than regular MTBs.

Shorter chainstays reduce the bike’s wheelbase and make lifting the front wheel effortless because the rider doesn’t have to move much to get their weight behind the rear axle.

In addition, shorter chainstays render the bike more playful and responsive.

In different, hardtails have longer chainstays for more stability during high-speed riding.

The shorter chainstays of a dirt jumper make it less stable for demanding descents and increase the chances of looping out (the bike sliding in front of you).

If you want to learn more about the differences between short and long chainstays, consider reading this article dedicated to the topic.

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.

Frame Size

Trail bikes come in a variety of sizes designed to accommodate most riders out there.

Conversely, many dirt jump manufacturers produce uni-size models. This peculiarity increases the difficulty of finding a dirt jumper comfortable for trail riding.

If you want to know more about dirt jump sizing, consider reading this post.

Frame Weight

Dirt jumpers are simplistic single speed bikes designed for hard impact landings. The frames are often extra strong and therefore extra heavy in comparison to hardtails. Sometimes a single speed dirt jumper ends up heavier than a geared MTB.

Accessories

Dirt jump frames have no eyelets for fenders, racks, or water bottles (sometimes you can’t even fit a water bottle because the triangle is too small).

This is another reason why dirt jumpers aren’t optimal for long rides.

The table below summarizes the frame differences between hardtails and dirt jumpers.

Suspension Forks

Dirt jumpers use a fork with relatively short travel between 80 and 100mm. The most common travel length is 100mm.

The reasons for the short travel are:

1. Steep head tube angle

A fork with a long travel slackens the geometry of the bike. The result is a loss of maneuverability hurting dirt jump performance.

2. Stiffness

Dirt jump forks are meant to absorb hard and relatively infrequent landings. For that reason, they are kept stiff. Short travel helps with that goal.

Meanwhile, the fork travel of modern hardtails often exceeds 120mm and sometimes reaches even 140mm. The extra travel results in a plush fork and makes it easier to cover hard terrain.

Below you will find the fork travel of the models used in previous tables.

Note: Since dirt jump frames are overbuilt, many models can take forks with ridiculous travel. However, the overall geometry of the bike rarely agrees with extra-long forks.

Conclusion: The stiff suspension fork of a dirt jumper often has insufficient travel to match the performance expected from a dedicated hardtail.

Different Wheel Sizes

Modern MTB bikes use 27.5 and 29-inch tires whereas dirt jumpers rely on 26-inch wheels and occasionally 24-inch.

The reasons why dirt jumpers use smaller wheels are:

1. Durability

The smaller the wheel, the stronger it is.

2. Maneuverability + Precision

26-inch wheels offer more maneuverability and precision than larger sizes.

The wheel sizes may be different, but this point isn’t a deal-breaker. Not long ago, all mountain bikes had 26-inch wheels.

Gearing

Most dirt jumpers come in single-speed mode for simplicity and weight reduction. This makes dirt jumpers inefficient for actual cycling.

In different, MTBs offer a fairly wide gearing range allowing the rider to cover more distance while exerting less effort.

Having said that, it’s possible to install gears on a single-speed bike. Here’s a dedicated article on the topic.

Brakes

A dirt jumper typically comes with a rear brake only to facilitate the execution of tricks such as bar spins. A single brake is insufficient for trail riding. You need two brakes of great quality.

This issue is easily fixable because dirt jumpers have front suspension forks with a mount for a disc brake caliper.

Multi-Purpose Dirt Jumpers

There are also “in-between” dirt jumpers and hardtails that can work as multi-purpose bicycles:

Example models:

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

What Are The Main Downsides of Using A Dirt Jumper On Trails?

1. Small size

The average dirt jump bike is too small for taller individuals when used for trail riding.

2. Steep Head Tube Angle

The steep head tube angle makes dirt jumpers less stable during downhill descents. A dirt jumper would have a hard time covering the aggressive terrain that a modern trail bike can ride on.

In addition, the steep head tube increases the chances of getting over the handlebars.

3. Unstable

The shorter wheelbase and chainstays of dirt jump bikes make them less stable during high-speed trail riding and greatly increase the chances of looping out.

4. Lack of a rear suspension

Most dirt jumpers come without rear suspension. In consequence, their rear end isn’t as stable during off-road riding.

Despite the downsides, a dirt jumper can still be used on trails with caution and lowered expectations. The bike just isn’t optimized for similar riding and one should expect lower performance, poor comfort and a greater chance of falling.

What Are The Main Downsides of Using A Dirt Jumper As a Cross Country Bike?

A true dirt jumper makes for a poor cross country bike for the following reasons:

1. Inefficient and uncomfortable pedaling

A good XC bike can be pedaled comfortably and efficiently from a seated position. A dirt jumper would have a hard time matching that level of comfort.

Of course, you can put a longer seat post, but that modification doesn’t always produce the desired results. On some frames, the seat post angle is just too slack, and you have to pedal in a position too far behind the bottom bracket.

In addition, people with long legs will have a hard time finding a long enough seat post.

A stock seat post is about 30cm and has a minimum insertion length of 10cm. Some riders will have to look for very long custom seat posts to get a halfway comfortable seated position.

2. Compressed Riding Stance

XC bikes have longer stems and frames allowing comfortable seated pedaling. A dirt jumper, on the other hand, puts you in a cramped, non-aerodynamic position.

3. No gears (on some models)

4. Stiff, less forgiving forks

Can I Use a Dirt Jumper As a Commuter?

A standard dirt jumper could work as a commuter only for short distances up to 3-5km. Anything more than that increases the risk of getting joint pain due to pedaling out of the saddle all the time.

If the model is closer to a hardtail and offers acceptable seated pedaling, the range will go up greatly.

But even in that case, a dirt jumper won’t be able to match the performance of a dedicated commuter for the following reasons:

1. Non-aerodynamic riding position

2. No gears (possibly)

3. No mounts for fenders, racks, and water bottles

4. Shorter chainstays result in pedal strikes against panniers (if you manage to install a set in the first place).

Can I Use My Trail Bike as a Dirt Jumper?

You could, but it will be more difficult to perform tricks because the bike is larger and longer.

There’s a reason why people use dirt jumpers for dirt jumping – the bikes are optimized to excel at that activity.

Summary

• Dirt Jumpers aren’t ideal for trails and commuting unless you’re willing to make some big compromises. Nonetheless, the setup could be acceptable in some cases.

• Some dirt jump models are “in-between” and work as an MTB to more satisfying levels.