How to Choose a Dropper Seatpost

INTRO

Dropper seatposts are an excellent way to expand the capabilities of your bicycle. Dropper posts have become very popular with modern Mountain bikes. They are also being used on some Gravel bikes. You can set your seat to the right height for efficient pedaling and then lower the saddle when you begin your descent. You can move your bike beneath you without any obstructions, which will allow you to be in a better position to tackle the challenges of the trail. For technical sections, you can lower the saddle slightly.

It can be difficult to get the measurements right to ensure compatibility, performance, and functionality. This guide will answer all your questions and help you choose the best seatpost for your bike and you. You can always contact us if you are still unsure after reading the guide. We will direct you to the right post for you.

This guide will show you how to measure each measurement and then translate them into the correct dropper post.

Key Measurements:

• Diameter
• Total/Overall Length
• Minimum Insertion Length
• Maximum Insertion Length
• Usable Height/Stack Height
• Travel

Diameter

The distance between the side of your seatpost and the back.

Total/Overall Length

Distance from the bottom (excluding any actuation mechanism) of the post to the middle of saddle rail clamps.

Minimum Insertion Length

Seatposts have a horizontal line that indicates the "Minimum Insertion" point. This indicates the minimum amount of seatpost that must be installed in your frame's seat tube for safety. Never ride your seatpost below this line.

Maximum Insertion Length

The distance measured between the bottom of a post (excluding an actuating device) and the bottom of a seatpost collar. The maximum insertion distance of your frame may also be less than the seatpost. This is referred to as the FRAME MAX Insertion Length, determined by the distance between the seat tube collar and the first bend or bolt in the frame.

Stack Height

This is the distance between the bottom of the seatpost collar and the middle of saddle rails clamp. You can also get this number by taking the overall length minus the maximum insertion distance. Stack height plus any exposed seatpost between your frame's seatpost and dropper seal collar is the usable height. Max Seatpost Height = Distance between the top of the frame's seat collar and the middle of the seat rail clamp, when riding with your legs fully extended.

Travel

The distance between the top of your seatpost collar and the bottom of the ebike saddle head is the length of the exposed stanchion.

THE STEPS

After we have looked at the different dropper post sizes, let's look at how you can use these measurements to find the best post for your bike and riding style.

STEP 1

To find the best dropper post, you must first determine how your frame routes its remote cable. The majority of newer frames have the option to route the remote cable to the actuator mechanism at the bottom dropper post. This is also known as "stealth routing" or an internal dropper. Some frames have only external routing and require a dropper with the actuating mechanisms outside the frame, at the seal collar of the dropper or the saddle clamp.

STEP 2

Next, determine the inner dimension of your frame's seat tube. The seat tube and seat post diameters should be the same. This measurement can usually be found on your seatpost or in your frame specifications. Seatpost shims can be used to accommodate a smaller dropper diameter, but they introduce an additional part that could cause your seat to slip or twist. The most common diameters are 31.6mm, 30.9mm, and 27.2mm, with 34.9mm also becoming more popular.

STEP 3

You will then need to find the stack height for your frame. The stack height is the combination of the dropper-post collar plus travel and the saddle clamp (measured in the middle of saddle rail clamp). The stack height must be equal to or lower than the maximum seatpost height. We aim to match the maximum seatpost height with the usable seatpost height plus 15-20mm below the collar for some fine-tuning flexibility. If the stack height is higher than the max seatpost height, it will reduce the travel you can use.

STEP 4

Determine your frame's maximum insertion length. This will tell you what the maximum insert length is for your dropper and may affect the height. Adding about 15-20mm to your seatpost measurements is recommended for fine-tuning.

Watch out for these things

You may find that different brands have a different range of travel due to differences in the height of the saddle clamp and seatpost collar. Internals can also affect maximum insertion lengths for posts with the same travel. Internal actuation mechanism variations can add 30-80mm to the maximum insertion, so be sure to consider this when choosing your next dropper.

The stack height of your saddle is also a factor. A saddle with a shorter stack height will give you more room to work with in your seatpost travel.

Your riding style will determine the amount of travel that you need. Trail and enduro bikes benefit from longer drops (125-180mm), while XC and Gravel bikes require less travel (60-100mm). Frame size, rider height, and frame geometry can limit the travel of a dropper post. Travel numbers should be considered last, as they depend on many other factors.