Bike dropouts and fork ends are vital parts found on a bicycle’s frame and fork, respectively, serving as the attachment points for the wheels.

Positioned at the rear of the frame and the tips of the fork blades, they feature slots or openings where the wheel axles are inserted and secured.

Available in varied designs such as horizontal dropouts, vertical dropouts, and track fork ends, these elements fulfill various functions, including chain tension adjustment, wheel size accommodation, and stability enhancement.

Integral to wheel alignment, secure wheel attachment, and overall bike performance, dropouts and fork ends are indispensable in ensuring a smooth and efficient ride.

In this guide to the humble bike dropout and fork end, we’ll be getting you up to speed on:

What Is A Bike Dropout?

A derailleur hanger pictured on its own (left) and as it appears when fixed to the bike’s dropout (right).
Credit: Glory Cycles, CC BY 2.0. Modified from the original.

Let’s start with bike dropouts. These sit on the rear of the bike frame and are the mounting point for the wheel’s quick-release axle to grip onto.

They’re sometimes referred to as “rear dropouts”, but this is a bit of a misnomer as the attachment points for the front wheel are called fork ends rather than dropouts.

The dropouts are also the connecting point for mounting the rear derailleur, usually via a small metal piece that bolts onto the dropout called the derailleur hanger.

Some modern dropouts are different from traditional designs, and instead of using a quick-release skewer, they use a thru-axle to secure the wheel to the frame. Later in this article, we’ll discuss the modern standards of dropouts and fork ends.

Another thing you might see on a dropout is what is referred to as an eyelet. This is a small screw hole near the dropout, which has the ability to attach a rear rack or mudguards to it. They are often seen on touring and commuter bikes.

Different Types Of Bike Dropouts

There are a few different types of dropouts available on bikes. Here are the most common types you are going to see.

Vertical Dropout

Vertical bike dropout and derailleur hanger on my mountain bike.
© Robbie Ferri/BikeTips

Firstly, we have a vertical dropout. This is the most common type on modern bikes.

When you undo the quick-release lever, the wheel can drop straight out downwards (once the chain is moved by pushing the rear derailleur back).

Vertical dropouts have one fixed position for the wheel to sit, so when they are inserted into the bike, they should be seated perfectly inside, gripping the dropout’s edge. Turning the bike upside down when installing a wheel ensures this, although there’s room for play. 

Horizontal Dropouts

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Then, we have horizontal dropouts. Usually they’re not strictly horizontal, but they’re at a much more pronounced forward-facing angle than vertical dropouts.

These are an older design, commonly found on classic road bikes, but were largely replaced in the 1990s by horizontal dropouts.

They typically featured long dropout slots, and were a little more fiddly to get the wheel in and out of than modern designs. It’s rare to find a modern bike fitted with a classic-style horizontal dropout.

Horizontal dropouts on steel bikes typically included the derailleur hanger as part of the frame itself, connected to the dropout, rather than a separate detachable metal piece as is the case on most modern bikes with horizontal dropouts or thru-axles.

Track Fork Ends

Close-up of a track fork end.
Credit: Glory Cycles, CC BY 2.0. Edited from the original.

Confusingly, many cyclists also refer to these as “horizontal dropouts”, but they’re a very different design to the above.

Unlike horizontal dropouts, track fork ends are actually horizontal, and open towards the rear rather than the front of the bike.

Track fork ends are found on bikes without rear derailleurs, such as track bikes, fixies, and single-speed bikes. Their purpose is to allow you to move the wheel forward or backward slightly, enabling you to maintain chain tension without the spring-loaded arm of a derailleur.

You will find some track fork ends with screw adjusters, which means you can dial the measurement in perfectly or achieve ideal tension.

Thru Axle Dropouts

Thru-axle dropout on my gravel bike.
© Robbie Ferri/BikeTips

Thru-axles have emerged as a popular alternative on modern road, mountain, and gravel bikes, especially those with disc brakes, due to their extra secure fastening of the wheel.

This different attachment system requires a different dropout. Instead of a conventional vertical dropout, frames designed for thru-axles use hole-shaped dropouts, which the axle screws into.

What Is A Fork End?

Upturned fork end on my road bike.
Upturned fork end on my road bike. © Robbie Ferri/BikeTips

Now, let’s move to the front of the bike and discuss fork ends.

Note that here we’re talking about conventional front fork ends you’d find on all bikes where the front wheel attaches, rather than track fork ends which are on the rear of the frame and specific to track bikes and single-speeds.

Regular fork ends are much simpler than dropouts because they don’t need to accommodate a derailleur or maintain chain tension. Their sole job is to keep the front wheel secure and aligned.

Thru-Axle Fork End

Thru-axle fork end on my road bike.
© Robbie Ferri/BikeTips

The main variation from conventional front fork ends you’re likely to see is on bike frames designed for use with thru-axles.

These use a hole into which the axle is screwed, instead of a vertical slot that the wheel slides into.

Can You Change Dropouts On A Bike?

We occasionally get asked if you can change the dropouts on a bike, usually by cyclists looking to convert a road bike to a fixie or vice-versa.

The answer is – it’s complicated.

To change the dropout itself would require cutting it all out and then installing a completely new dropout system. This would take a very talented welder and likely cost significantly more than a replacement frame.

There are some adapters on the market that can help.

For example, you can buy an adapter to convert a road bike with a vertical dropout to a track fork end, so that you can set up a single-speed or fixed-gear drivetrain.

I’d urge caution with this, however, as you might compromise the bike’s safety by weakening the wheel’s attachment point.

Some companies also offer replacement dropouts that can be used with different axle types. I once converted a Lynskey Sportive road bike from a quick-release dropout to a thru-axle just by changing the hanger and an adaptor on the other side. 

If you want to go down this route I recommend trying to avoid a bodge solution. Go and see a local bike shop and ask an expert their opinions to if it is going to be possible and whether it will be safe. 

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