Tips to Choose Mountain Bike Saddle Rail Size

Saddle rails are a vital component of any bike's saddle. They connect the saddle to the seat post and make the cyclist’s ride more comfortable. The rails are responsible for supporting the cyclist's weight. The stronger and better fitted the rails are, the better support they provide. Seat rails also allow the seat position to be altered for maximum comfort, so you need to choose the right mountain bike saddle rail size which fit the mountain bike frame. 

Most saddle rails are 44 mm wide. 7x7mm saddle rails are used on standard bikes, high-performance carbon bikes use 7x9mm saddle rails, and 7x10mm oversized rails are used for extra strength and support. 

In this article, we provide tips for choosing mountain bike saddle rail sizes to help you learn more about the different sizes available and how to choose the best one for your bike. Our article about choosing a mountain bike saddle will also help you determine what saddle type best suits your body. 

Mountain bike saddle rail sizes are important for attachment to a seat post.
Saddle rails help riders adjust the saddle position on the seat post. Image Source: Amazon.

What Are Mountain Bike Saddle Rails?

Mountain bike saddle rails run along the underside of the saddle from the nose to the rear and connect the saddle to the seat post that is fitted into the seat tube on the bike frame. Saddle designs vary but the most common saddle design comes with two parallel rails to which the seat post clamps. Other designs include one to four rails. 

Bike saddle rails are rails that run under the saddle and connect it to the seat post. Saddle rails allow riders to adjust their seat position, angle, and fit. Saddle rails can absorb shocks, and protect the seat against damage.

One useful feature that saddle rails offer is they allow the rider to make fore and aft adjustments to the saddle by moving the saddle toward the front or the rear of the bike. Our tips to adjust a mountain bike seat angle give an in-depth explanation of these angles and how they can improve the rider’s comfort. 

Saddle rails support the weight of the cyclist and protect the seat against possible damage. They’re designed to be strong and shock resistant so that they provide support and a more comfortable ride. However, according to this article from Procedia Engineering, the strength and support the saddle rails offer depends on the quality of the rails. 

The materials used to make saddle rails play a vital role in the final quality of the product. The most common materials for saddle rails are steel, alloy, carbon fiber, titanium, aluminum, and manganese. Steel makes durable and strong rails but it's heavy. If you're looking for lightweight material, then steel isn't right for you. 

Alloy rails are stronger and lighter than steel. It's a great material if you're looking for strength and lightweight features. Titanium rails like these and carbon rails like these are great choices. They’re both strong and light, great at resisting shocks and absorbing vibration. Still, both are expensive compared to other materials. To find the right mountain bike saddle materials for your needs, be sure to check out our article.

Mountain bike saddle rails allow you to shift the saddle forward or back so that you sit in the perfect position on your bike.
Saddle rails run along the underside of the saddle to where the seat clamp mounts connect the saddle to the seat post. Image source:

You may find interest in learning if bike saddles are universal. Be sure to check out our related article for compatibility tips and tricks.

Mountain Bike Seat and Saddle Rail Size Compatibility

Saddle rails connect the saddle to the seat post of the bike. The part that connects both of them together is known as the "saddle clamp." The clamp is attached to the top of the seat post and it needs to be compatible with the saddle rails configuration. 

To ensure that a bicycle saddle is compatible with a seat post, first determine that the seat clamp fits onto the saddle rails as well as the seat post. 

Two-rail 7 mm round saddles are common, but some other saddle shapes need different types of seat clamps to be compatible. Non-carbon saddles like this are made with 7mm rails that are compatible with all standard seat post clamps. Conversely, carbon saddles are made with oval rails that are 7mm wide X 9mm tall, requiring a seat post clamp compatible with the 7 x 9mm size for carbon saddles like this.

It's necessary to ensure that your saddle rails are compatible with the seat post clamps. If the size does not fit, extra stress will be added, making the saddle rails break or bend. Our article about how to fix a mountain bike saddle that keeps moving explains what the effects of ill-fitting saddles are.

Are MTB Saddle Rails Universal?

Mountain bike saddle rails like these are generally universal in size (7x7mm and 44mm width) but can vary depending on the type of saddle rail material the rider prefers. Non-carbon saddle rails are available in the standard 7×7mm size. They’re round rails that can fit with standard seat post clamps. Carbon saddle rails, on the contrary, are oval and are 7mm × 9mm in size. This type of rail requires different kinds of seat post clamps that can fit different configurations.

Most mountain bike saddle rails are universal, measuring 7x7mm and 44mm in width.

The saddle materials and design affect the size of the rails. Apart from the standard two-rail design, there’s also a design that consists of only one large rail like this and tripod saddle rails like this. All of these different designs require different types of seat post clamps.

Most mountain bike saddle rails are universal to be compatible with different types of mountain bikes.
Saddle rails come in standard sizes so that they are compatible with more bikes. Image Source: Amazon.

44mm Bike Saddle Rail Width Is the Industry Standard

44mm is the average saddle rail width that fits standard mountain bikes. This width must be compatible with the seat post adapter. When you purchase a new saddle, you can ask about the width of the rails to make sure it is the standard width. You can also look for a label that says universal or standard. You can find saddle rails with different widths but this won't be a problem. If they are close enough in width, they can still fit; all you need to do is to bend the rails a little or install a saddle rail adapter like this one. 

The rail width of a mountain bike saddle is the width between the two rails under the saddle.
Rail width is the space between the two rails that run along the underside of the saddle. Image Source:

7mm Saddle Rails Are Found On Most Mountain Bikes

Non-carbon saddle rails like these are made with round 7mm rails. This sizing saddle rail is standard for mountain bikes because non-carbon rails are known for strength and support.  Different sizing is common with carbon rails but they are not commonly used for mountain bikes. Most riders prefer the non-carbon 7mm rails because they can withstand hard rides and jumps compared to carbon rails. If your saddle is not soft enough, be sure to read our steps on how to fix a mountain bike saddle that feels too hard.

The universal size for mountain bike saddle rails is 7mm.
7mm Saddle rails like these are the standard size for mountain bikes. Image Source: AliExpress.

Alternative Mountain Bike Saddle Rail Sizes

Even though there’s a standard size, some mountain bikes need a saddle rail size that’s outside the norm. This can be because of the material of the saddle or if you need an oversized saddle. 

Typical bike saddle rails are 7x7mm. Alternative mountain bike saddle rail sizes include 7x9mm carbon saddle rails, and 7x10mm oversized saddle rails. 

Read our article comparing mountain bike seats and trekking seats to find out more about the various seat sizes and styles that are available.

Take a look at the alternative saddle sizes:

Alternative Size 1. Carbon 7x9mm Saddle Rails   

Carbon oval saddle rails like this measure 7x9mm and are one of the common types of saddle rails that mountain bikers opt for. Cyclists often prefer carbon saddle rails for higher performance. As this article from Sponet explains, carbon saddles are low weight, more comfortable, and improve the overall cycling experience. 

Carbon saddle rails are safer because of their excellent vibration damping and providing a smoother ride. However, carbon saddle rails are not compatible with standard seat post clamps and require a specialized one like this

Alternative Size 2. 7x10mm Oversized Saddle Rails

Saddle rails like this that measure 7 x 10mm are referred to as oversized saddle rails. Many cyclists choose this size for extra strength and support. It is typically used for mountain bikes and BMX because of its strength and durability. This size saddle rail is not compatible with the standard saddle clamp and it requires a specialized one designed to be used with oversized saddle rails. 

Saddle Rail Size Summary

Saddle Rail Sizes When to Use Example  Approximate Price
Standard 7x7mm If you are looking for support and comfort during rough rides - Mountain Biking Ritchey Comp Skyline Saddle Rails ~$50
Carbon 7x9mm If you want a lightweight saddle and comfort is your priority Fizik Aliante R1 Saddle Carbon Braided Rails ~$290
Oversized 7x10mm If you're looking for extra support and strength Fizik Argo Vento ~$160

You might also be interested in reading our quick guide to mountain bike seat replacement. If so, be sure to check out our related article for more information.

What Are the Reasons to Use a Saddle Rail Clamp?

Generally speaking, if your mountain bike uses non-carbon 7mm saddle rails, you'll need a standard saddle clamp to connect the saddle to the seat post. This is because the 7mm size is the standard size for saddle rails and it is compatible with any standard size saddle clamp. If your bike can accommodate 7×9 or 7×10 oversized rails, you'll need to get a specialized clamp to be compatible with them. 

Use a standard saddle rail clamp to accommodate 7×9mm or 7×10mm saddle rails.

A 7x7mm saddle rail can be attached to using a standard rail clamp.
Standard rail clamps fit 7x7mm saddle rails. Image Source: Amazon.

What If My Replacement Saddle Rails Don’t Fit?

If your saddle rails are too wide or too narrow, you don’t need to buy a new seat clamp. To fix this problem, you'll need pliers and a shim or spacer. If the rails are too narrow, you will need to increase their width by bending them a little. If they are too wide, you will need to increase the size of the seat post with spacers so the rails can fit. The section below explains in detail how to fix wide or narrow saddle rails. 

If the replacement saddle rails are too wide, use an adapter to make them fit. If the replacement saddle rails are too narrow, use a shim or a spacer to increase the width of the seat post until it is compatible with the rails.

Tools to Adjust Seat Rails That Don’t Fit

Tool or Accessory How To Use the Tool Example Product from Amazon Price
Pliers With the pliers, gently bend the rails until they fit onto the seat post Boosden Linesman Pliers, 6 Inch, High Leverage Lineman's Pliers ~$10
Shim  Use the shim on the seat post to increase its size to be compatible with the rails  5mm Spacer Shim Set ~$10

How to Fix a Bike Where the Bike Saddle Rails Are Too Narrow

If your saddle rails are too narrow, you can simply bend them a little until they fit. For this process, you'll need pliers from a set like this or a vice like this. Use the pliers to bend the rails until they fit into the seat post clamp. Don't worry about the rails being damaged. Rails are made of metal and bending them while being careful won't be a problem at all. If you’ve fixed the issue and your mountain bike saddle is still uncomfortable, check out our article on how to reduce mountain bike saddle pain

How to Fix a Bike Where the Bike Saddle Rails Are Too Wide

It’s easy to make too wide saddle rails fit. All you need is a shim set like this or spacers to increase the width of the seat post a little. Attach the shim to the seat post to increase its width until it’s right for the size of the saddle rails. This is easier and cheaper than purchasing a new seat post. If you would prefer to purchase a new seat post then read our article about seat post extenders to learn how they can improve your comfort on a mountain bike. 

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