What is a Dropper Post on a Mountain Bike (Understanding Your MTB)

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If you’ve heard the phrase ‘dropper post’ in mountain bike conversation, then you might be wondering what it means. Unlike some MTB terms which are fairly logical (think: hardtail or suspension forks) it can be a little difficult trying to fathom out what this one might mean. We’re going to dig into what a dropper post is, how they work, and why you’d need one on your bike. We’ll also look at the costs of adding one to your existing rig, whether your bike is dropper-compatible and, if so, what size dropper post you’d need.

What is a dropper post?

A dropper post (AKA a dropper) is a seatpost that can raise or lower very quickly to adjust the saddle height to the optimum position for the riding at that moment. It’s operated by a trigger mechanism on the handlebar, so you can activate it without stopping and getting off your bike.

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Why would I need a dropper post?

A dropper is one of those bike components that, once you’ve got one, is hard to imagine how you ever managed without it.

With a quick-release seatpost clamp (or, heaven forbid, a hex bolt one…shudder) changing the seat height requires you to:

  1. Stop cycling
  2. Get off the bike
  3. Undo the quick-release seatpost clamp (or select the allen wrench on your bike multitool and unscrew the bolt)
  4. Raise/lower the post (ensuring that the saddle is still pointing vaguely towards the front wheel)
  5. Re-tighten the seatpost clamp with either the snappy quick-release or the time-consuming hex bolt
  6. Get back on your bike
  7. Start cycling again

This all takes time, of course. Your riding buddies won’t be happy and you’ll get no end of ‘friendly’ abuse about it if you do it too often.

Generally, this means that you won’t change the saddle height as often as you should, and that leads to potentially unsafe or inefficient mountain biking.

Downhill cycling with a saddle that’s set too high, preventing you from lowering your center of gravity to help maintain balance.

Uphill cycling with the saddle too low, preventing you from fully extending your legs with each pedal stroke, and therefore sapping the strength in your quads.

Ok, what’s life like with a dropper?

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How does a dropper post work?

Much safer and much more efficient, that’s what life is like with a dropper post.

So, how do droppers work and how do you use them?

Dropper posts are essentially a system that comprises three components:

  • The dropper post itself
  • Cabling connecting post and trigger
  • Trigger mechanism

The dropper post is very similar to hydraulic forks – an outer cylinder that fits inside your seat tube and is clamped in position. Inside this is an inner cylinder that can slide up or down and operates via pneumatic force.

On most models metal cabling is used to connect the post to the trigger (though a few wireless models are now starting to appear too).

The trigger mechanism is attached to the handlebars and consists of a single lever.

Using the dropper is simple:

  • Sit on the saddle, press the lever – the saddle descends by a set amount to the minimum height (the ‘stroke length’)
  • Lift off the saddle, press the lever – the saddle ascends to the maximum set height

Throughout this transition you can keep pedalling or freewheeling, and there’s no need to hop off the bike and start hunting in your pockets for allen wrenches.

Convinced? Yeah, then let’s take a look at the specifics of how much droppers cost and how to pick the right one for your bike.

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How much does it cost to add a dropper post?

For the parts, including dropper post, cabling, and remote lever, you should expect to pay around $250-$350 for a good quality set that works for either a mountain bike or an eMTB.

When you’re choosing the remote lever keep in mind that these come in two different flavors, depending on whether you have a 1x or 2x/3x drivetrain. Why? The remote lever attaches to the left of the handlebar. With 1x drivetrains, the remote lever won’t be competing with gear shifters – so choose a 1x remote lever. For 2x or 3x drivetrains, you will have gear shifters on the left so will need to go with a 2x remote lever. They operate the same, but 2x remote levers hang down from the handlebar to avoid clashing with the gear shifters.

Installation can be done yourself (YouTube is your friend, as always). If you’re a little unsure about your technical abilities, then a LBS will fit this for you. For externally routed cabling (non-stealth) the cost should be $15-$25. For internally routed cabling (stealth) the cost will likely be $20-$40.

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How do I know if my bike is dropper post compatible?

There are a number of factors to look at when choosing the right size dropper, and knowing whether a dropper post will be compatible with your bike.

Seat tube diameter – droppers come in four common external diameters and you need to pick the diameter that matches your bike (check your existing seatpost, which should have the diameter printed on it in millimeters). Commonest diameters are: 27.2mm, 30.9mm, 31.6mm, and 34.9mm.

Maximum seat tube insertion length – how far will the dropper be able to slide into the seat tube before it hits an obstruction? Check this is enough to give a secure hold without too much sticking out of the top of the tube.

Travel – check the length of travel of the dropper to ensure it gives you the correct range (a great sweet spot is around 150mm/170mm).

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There you have it. Dropper posts are remotely-operated adjustable height seatposts for your mountain bike. Allowing you to swap between maximum height for efficient uphill pedalling and minimum height for safe descents, all at the push of a lever installed on your handlebars.

Try them for yourself, and you might well find that droppers become an indispensable part of your mountain bike setup. Upgrading your safety, dialling up your efficiency, and enabling you to roll your eyes at any of your riding buddies who haven’t yet taken the plunge and got one. As they hop off their bike, yet again, and reach for the allen wrench.

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