Swapping bike saddles is pretty simple with one standardized mounting type being used almost universally: the standardized dual rail.

But not all bike saddles fit on any bike because there are four standardized saddle mounts available:

  1. dual rails
  2. single rail
  3. pivotal
  4. tripod

As long as the saddle and seatpost use the same mounting type, they are compatible since they are all standardized.

four standard saddle mounts: dual rail, monorail, pivotal and tripod
The four standard types of bike saddle mounts: dual-rail, monorail, tripod and pivotal.

But as I said: Most bicycle saddles are universal, using the dual-rail mount that fits on a standardized seatpost.

The standardized width between the two rails is 44 millimeters. Though, there are seatposts and saddles using other mounting systems like single rails, pivots and rigid tripods.

Saddle rails are universal

Saddle rails are standardized in the dimensions that matters: width and rail thickness. The two parallel rails are 44 mm apart and match the universal seatpost clamps.

Saddles using one rail, called monorail, are also universal in their dimensions but only fit monorail seatposts. The rails are used to allow the saddle to slide back and forth for a proper bike fit.

Atherton AM.170 Enduro saddle
Regular old dual rail saddle and seatpost.

Rail materials

Rails make up a big portion of the saddle’s overall weight. Accordingly, there are a couple of different rail materials to choose from, varying in weight and stiffness (read comfort).

Depending on the material, the rails can also offer slight vibration dampening. High-end, expensive but light Carbon rails are pretty stiff usually.

This makes them a great option for riders for maximum pedal efficiency and minimal dampening (and maximum sore butt).

Metal rails like titanium or alloy rails are the most common ones. They are found on mid-level performance saddles and provide a smoother ride by being not so stiff. Prices are usually much lower but can be double the weight of carbon rails.

Replaceable rails

Generally, rails on a bike saddle can be replaced. Saddle rails are designed to be the pre-determined breaking point (rather bending point), so they are built with repairs in mind. They are also the cheapest part of the saddle, making it last longer with minimal maintenance cost.

The rail replacement can be done in a bike shop for between $ 25 and $ 40 including parts. The rails themselves can be bought or ordered like any other bike part. The exact price will vary depending on the manufacturer and the materials used.

However, if you manage to bend the saddle rails, the whole saddle is usually destroyed or broken in some way.

Saddle swap

If you ever tried it, you know replacing dual rail saddled can be finicky. Here’s how to do it in under 10 minutes:

Putting a regular bike seat on an exercise bike

If it has a saddle clamp, a regular bike saddle can be mounted on a stationary bike no roblem.

Generally, that’s the case for most spinning bikes but only for the minority of bicycle ergometers. Saddle clamps usually fit regular dual rail bike seats, which are universal and the most common.

Dual rail saddles are so universal, that they even fit on bikes that don’t even move.

The difference between a spinning bike and a bike ergometer is the overall design. While spinning bikes are more akin to road bikes in terms of geometry, handlebars, pedals and saddle, other exercise bikes are designed for comfort. Often sporting a wide, cushy saddle, upright body position and a screen for stats.

In fact, I swapped regular bike seats on my stationary spin bike using a seat clamp adapter for rail saddles. The one I have came with the spin bike, but those can be had for under $10 on amazon.

This adapter clamps around the seatpost (which is just a short tube in my case) and has the standard rail clamps on top to mount any rail saddle onto.

It’s the same solution you would use to make older vintage bikes compatible with modern saddles.

It’s very easy to install, as there is only one hex-head screw nut on the side, that tightens the whole mount.

Swapping the seatpost – what to look out for

For anyone who wants to fit completely different types of saddles on their bikes, you need to swap the seatpost to do so.

seatpost, seat clamp and seat tube are located from top to bottom on a bike
I will be talking about these three parts a lot going forward, so here they are marked on my bike: seatpost, seat clamp and seat tube.

The current five standard seat tube diameters are 27.2 mm, 28.6 mm, 30.9 mm, 31.6 mm, 34.9 mm, and 36.4 mm. The most common seat tube diameters on mountain bikes are 27.2 mm (standard), 30.9 mm and 31.6 mm (oversize).

Older bikes used to have many more seat post diameter options varying in 0.2 mm increments.

In order to measure the diameter of your seat post, you need to dismount it and pull it out of the bike frame. This is done by simply loosening the seatpost clamp.

Simply take a measuring tape to the bottom end of the seat tube to accurately measure its outside diameter. Same for the inside diameter of your bike’s seat stay.

There is no way to make the seat stay diameter of the bike frame any bigger. So a wider 31.6mm seatpost doesn’t fit a 30.9mm seatstay.

But there are methods to increase the seatpost diameter to fit a wider frame. For example a 30.9mm seat tube into a 31.6mm seatstay.

This is done by seatpost shims, that go over the seatpost to increase its diameter to fit larger diameter seatpost clamps.

There are a couple of brands and sizes to available. Reputable bike component brand Cane Creek has a broad selection of seatpost shims for any size combinations. Their shims are sold for around $10 to $15 on amazon.

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