What Is A Mountain Bike Dropout?

The Mountain bike dropout is not a topic of most conversations when it comes to mountain biking. These components are located on the fork-end and features a section in the frame or the fork, where the wheel can quickly be loosened and removed in the need of a wheel change.

In more technical terms, it refers to a slot located in the rear axle of the mountain bike, that allows the wheel to simply drop out. It enables the user to remove the wheel without the need to derail or remove the chain. While it could be dangerous if you don’t look after it, it is great for fast wheel changes in competitions.

The mountain bike dropout is described as such a technical aspect of the bike, but in reality, it is a very basic part of mountain bikes. Not all mountain bikes have this slot, but if your’s does, you should want to learn more. We have done some digging to better understand the mountain bike dropout and what it can do.

Mountain Bike Dropout Types

There are three different mountain bike dropout types, with the first one being the front fork dropout. The horizontal dropout is the other feature and it is often located more to the rear of the bike. If you want a better understanding of them, here is a concise breakdown of the mountain bike fork dropouts on your bike:

Front Fork Dropout

The front fork dropout is the more common of the three and most modern bikes have this located in the front fork. The dropout is often in the form of a skewer that simply turns to loosen the wheel. Once it has been turned enough, the front wheel will drop out of the fork. It is also important to hold the wheel in the frame efficiently.

Rear Derailleur Hanger Dropout

The rear derailleur dropout is another common part of modern mountain bikes and it attaches to the rear fork of the mountain bike. When fastened, it will keep the wheel in place, but it can easily be loosened to ensure your wheel will come loose. It is one of the cheaper components to replace on your bike, but also bends easily.

The great thing about the dropout is that should you fall, it could bear the brunt of the impact and take it off the frame. These components are much easier to replace than having to fix your frame. They are often cheaper to replace as well.

Rear Horizontal Dropout

The horizontal rear dropout is one of the least common features you could find on modern mountain bikes. While it might be functional for single-speed bikes, it can be hard to maintain some of the chain tension. These dropouts are commonly found on track bikes, with the front-facing dropout being more reliable for other bikes.

Another common downside comes with the setup of the unit. It depends heavily on the bolts to hold everything in place. A common complaint bike experts have found is that disc brakes will not work to their full capacity. You might often see that the axle bolts interfere significantly with the performance of these disc brakes.

Thru Axle Alternative

The other option that often serves to be better than the mountain bike dropout is the thru-axle. The component is slightly different and is an axle that goes through the bike. It is a hollow tube in the wheel that can be mistaken for a quick-release skewer. However, the difference is that the thru-axle only serves to hold the wheel. It does not necessarily provide the axle of the wheel.

Benefits Of Choosing The Thru Axle

Unlike the quick release skewer or traditional dropout, the thru-axle can be slightly better. There are a couple of benefits associated with having this component on your bike. It is easy for us to say that the thru-axle is better, but if you look at some of these benefits, you will notice how much better it tends to be.

  • Offers More Rigidity: Rigidity is something you only notice when climbing. When climbing a hill, more rigidity could reduce the effort and make it easier.
  • Durable: The thru-axle is slightly more durable and the structurally sound design means that it can handle more tension than the traditional quick-release skewers.
  • Cannot Come Undone: With a quick-release skewer, one slight bump could loosen the unit and make it risky. The thru-axle cannot be undone without the help of human assistance, which makes it safer.
  • Works Better With Disc Brakes: In terms of dealing with disc brakes, you want optimal performance. However, disc brakes and traditional dropouts could lead to the wheel being loosened. This can’t happen with a dropout.
  • Easier To Create Disc Brake Alignments: Should you service or make component changes on your bike, the thru-axle should work much better to create these alignments and repeat them.

The traditional dropout has always been what people wanted. They make it much easier to remove the wheel and should you be competitive, punctures and damage do not hinder you too much. However, the thru-axle might be more expensive but offers you better safety and more functionality when riding.

Frequently Asked Questions

Even though this is one of the minor components of the mountain bike, it is always wise to understand the components better. We have identified some of the most common questions from the internet that could help you. If you are looking to get the best performance from your mountain bike, here are a couple of things to keep in mind:

How To Fix A Rear Mountain Bike Dropout?

Falling with your bike is inevitable, especially if you are someone who constantly thrives on cycling. As previously mentioned, the rear hanger dropout can get bent. Since it is made from aluminum, you will want to consider bending it back. However, this should not come with the compromising of structural integrity.

It might even be easier to replace the rear hanger dropout instead of trying to bend it. Fortunately, it is one of the easier components to replace and it will not break the bank either.

Is It Possible To Replace All Mountain Bike Dropouts?

Unfortunately, the answer is not as clear-cut as many would like to believe. It will come down to the damage that is done and how handy you are with bending it. You should never risk the structural integrity of the component if you want to fix it. The upside is that these components are not expensive to replace.

Can The Mountain Bike Dropout Come Undone While Riding?

One of the first things that you should do as part of your checks is to ensure that these dropouts are secure. If you ride a couple of times, especially bumpy terrains, it could undo the dropout without you noticing. Riding your bike with a loose dropout could lead to plenty of damage and might even lead to potential falls.


The mountain bike dropout is one of the components that seems more complicated than it is. The easy way to envision the component is to think of the quick-release and you should always ensure that it is fixed and fastened. The components are often complicated, but if you have more questions, we would love to see some of your answers.

Below is a Pinterest friendly photo… so you can pin it to your Mountain Bike Board!