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.

1. Sizing

To work out your dropper size measure from the base of the collar
To work out your dropper size measure from the base of the collar

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
A bar-mounted remote controls the post via a cable or hydraulic hose

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
A locking mechanism holds the post in place and a spring pushes the saddle up when the lock is released

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
Dropper seatposts are available with 60 to 200mm of drop

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

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.

This article was originally published in Mountain Biking UK magazine, available on Apple Newsstand and Zinio.

Seb Stott

Technical writer, Tech hub, UK
Seb is a geeky technical writer for BikeRadar, as well as MBUK and What Mountain Bike magazines. Seb's background in experimental physics allows him to pick apart what's really going on with mountain bike components. Years of racing downhill, cross-country and enduro have honed a fast and aggressive riding style, so he can really put gear to the test on the trails, too.
  • Discipline: Mountain
  • Preferred Terrain: Steep!
  • Current Bikes: Focus Sam 3.0, Kona Process 111, Specialized Enduro 29 Elite
  • Dream Bike: Mondraker Crafty with Boost 29" wheels, a 160mm fork and offset bushings for maximum slackness.
  • Beer of Choice: Buckfast ('Bucky' for short)
  • Location: Bristol, UK

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