DROPPER POST BASICS

THE STEPS

Now, that we’ve looked at what the various dropper post measurements are, let’s delve into how to use those measurements to find the right post for you, your bike, and your riding style.

STEP 1

The first step in finding the right dropper post is determining your frame’s remote cable routing option.  Most newer frames are setup to run the remote cable internally to the actuator mechanism on the bottom of a dropper post.  This is known as an internal dropper or “stealth” routing.  Some frames only have external routing, and will require a dropper that has the actuating mechanism outside of the frame at the dropper seal collar or at the saddle clamp.

STEP 2

The next step is to determine your frame’s seat tube’s inner diameter. Your seatpost and frame seat tube diameter should match, and the measurement is usually printed on your current seatpost, or can be found in your frames specification lists.

It is possible to run a smaller diameter dropper with the use of seatpost shims, but this does introduce another part where slipping or twisting of your seat could happen. The most common sizes of diameters are 27.2, 30.9, 31.6mm with a newcomer of 34.9mm starting to become more common.

STEP 3

Next, you will want to determine the stack height that will work with your frame and riding position at full extension. Stack height is composed of the dropper post collar + travel + saddle clamp (measured at the middle of the saddle rail clamp). It is important that the stack height is equal to or less than your current max seatpost height.

It is okay for this measurement to be less than your current max seatpost height so long as you do not expose the minimum insertion point. As a general rule, we try to equal the max seatpost height to the usable height + ~15-20mm of exposed seatpost below the collar to give some fine-tuning wiggle room (usable height). If the stack height is greater than your current max seatpost height, it will be hard to reach the pedals and will make for an uncomfortable ride, or reduce the amount travel that you are able to use

STEP 4

Lastly, you will want to determine your frame max insertion length. This will determine what your maximum insertion length can be of your dropper, and may affect the usable height of your dropper. Using a dropper’s full maximum insertion length so that it sits collar-to-collar with your frame looks really “pro,” but it does limit the ability to fine-tune your fit. This is why we recommend including about 15-20mm of seatpost in your measurements

THINGS TO WATCH OUT FOR

Due to brand variations in seatpost collar and saddle clamp stack heights, the you may find that one brand allows you to have more travel for the same usable height measurement versus another. Also, different internals allow the various brands to have differing maximum insertion lengths for post with similar travel. Additionally, variations in internal actuation mechanisms can add between 30-80mm to your maximum insertion length. Be sure to account for this when choosing your next dropper post.

Another factor to be considered in this is the stack height of the given saddle that you use. A shorter stack height (from saddle rails to the top of the seat) will allow you more room to work with in your seatpost travel.

The amount of travel you need will depend on your riding style. XC and gravel bikes tend to need less travel (60-100mm) versus trail and enduro bikes which can benefit from long drops (125-180mm). Dropper travel can be limited by frame size, rider height, and frame geometry. We tend to consider consider travel numbers last because they rely on several other more crucial factors.