Condensed Answer: Many dirt jumpers do not have a front brake to facilitate the execution of tricks such as bar spins, save weight and prevent improper or accidental deployment of the front brake that may result in a fall.
Since dirt jumpers are not used for actual mountain biking, the absence of a front brake is not critical.
The Reasons Why Dirt Jumpers Come Without a Front Brake
- Free Rotation of the Handlebars
Dirt jumpers are designed for tricks some of which involve 360-degree rotations of the handlebars (e.g., bar spins). There are also tricks such as the tail whip during which the entire bike makes a 360-degree rotation around the fork’s steerer.
The cables of a front brake would prevent the above from happening. This problem could be circumvented by using a gyro brake system that makes it possible to spin the handlebars 360-degree even with a front brake.
The downside of the gyro system is the extra cost, weight, and mechanical complications.
- Lower Chances of Flipping Over The Handlebars
In an extreme situation, the rider may press the front brake aggressively (sometimes accidentally) while having too much bodyweight positioned at the front. As a result, the rider may fall over the handlebars.
In different, sudden, and intense deployment of the rear brake would lock the rear wheel and make it slide but will not directly “throw” the rider. In this scenario, the rider is less likely to fall because it’s easier to keep balance when the rear wheel goes “crazy”.
Note: In the case of disc brakes, the brake rotor could also present a potential danger during a fall/slip because it’s very sharp and can cut the rider. That said, this is a very custom scenario, and one cannot conclude that the absence of a front disc brake and thus a rotor eliminates a high-level danger.
- Extra weight
A front brake adds extra weight and clutter to the handlebars. The whole setup includes:
- Brake caliper
- Brake levers
- Cable + housing
- Brake Rotor (in the case of disc brakes)
- Weaker Wheel (in the case of disc brakes)
Disc brake calipers grab a rotor attached to the hub via bolts. Thе rotor makes it impossible to make the wheel symmetrically dished. Оne side of the spokes has to insert into the rim from a different angle to make space for the rotor.
All things being equal, asymmetrically dished wheels are weaker than symmetrical ones.
This issue can be circumvented by using a rim brake. However, most modern dirt jumper forks are designed for disc brakes by default and don’t have V-brake mounts.
Skipping the front brake allows you to have a dished wheel while using any fork you want.
Many riders want their bikes to look as clean as possible and do not add elements that do not compliment the original purpose of the bike which in this case is to perform jump stunts.
Another minor benefit in that category is that you won’t have to adjust the front brake. Or in other words, there’s one less setting to worry about.
The Downsides Of Riding Without a Front Brake
- Subpar Braking
The front brake offers more stopping power. During braking, the weight of the bike shifts toward the front wheel. Consequently, the front wheel gains traction while the rear one loses some. Hence why it’s so easy to make the rear wheel skid when braking.
For that reason, cyclists rely primarily on the front brake and many consider riding without a front brake extremely unsafe, especially if the bike is loaded and/or used on descents.
If a dirt jump bike is used for its main purpose, then the subpar braking power is not super detrimental because the terrain is pre-determined and doesn’t include mandatory stops. In the case of an MTB, however, a front brake is absolutely essential because the scenery changes quickly.
But if a dirt jumper serves for more than dirt jumping, the absence of a front brake could become problematic and even dangerous.
In that case, the rider has the following options:
- Buy another bike and use the dirt jumper only for dirt jumping.
- Add a front brake but accept that you won’t be able to perform some tricks.
- Add a front brake with a gyro brake system.
- Some Street Tricks Are Easier With a Front Brake
A front brake makes the execution of some tricks (e.g., endos) easier. That said, those tricks are more common for street and MTB riding rather than dirt jumping.