The anatomy of a dropper-post

Mystified by dropper seatposts? Here's a quick guide to how they work


Dropper posts are the latest must-have upgrade on mountain bikes these days, but if you’re a little confused by drop length or dropper remotes, here’s a quick guide to its inner workings for you to bluff your way through.

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1. Sizing

To work out your dropper size measure from the base of the collar
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The most common dropper diameters are 30.9mm and 31.6mm, but 34.9mm and 27.2mm posts are also available.

Most come in a choice of lengths, often linked to the amount of drop on offer.

Before buying, make sure the post is long enough when extended to give your preferred pedalling height. Measure from the base of the collar, not the bottom of the shaft.

2. Remote

A bar-mounted remote controls the post via a cable or hydraulic hose
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Most modern droppers use a handy bar-mounted remote to control the post via a cable or hydraulic hose.

Look for ones with an ergonomic lever that syncs well with shifters and brake levers.

Tip: if you have a RockShox Reverb and a 1x transmission, you can mount a right-hand lever under the left side of the bar to reduce the chances of damaging it.

3. Internals

A locking mechanism holds the post in place and a spring pushes the saddle up when the lock is released
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Inside any dropper is a locking mechanism to hold the post in place and a spring to push the saddle up when the lock is released.

Some also use a damper to slow the upward motion. The return speed of those without dampers can be a little alarming!

4. Drop

Dropper seatposts are available with 60 to 200mm of drop
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Posts are now available with 60 to 200mm of drop, depending on how low you want your saddle when descending.

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Some can be locked at any position within this ‘travel’ range these are often referred to as infinite, while others (such as Specialized’s Command posts) have a few preset heights.