Condensed Answer: A dropper post can be installed on a dirt jumper. However, there are some downsides to this practice because dirt jumpers aren’t designed to be ridden like a regular hardtail or commuter.
Dirt jumpers have a short wheelbase, small wheels and a compact frame making them impractical for biking activities outside of jumping and street stunts.
Requirements To Install a Dropper Post On a Dirt Jumper
- A Dropper Post of the Appropriate Size
The diameter of the dropper post should be compatible with the seat tube of the dirt jumper. Otherwise, the dropper post won’t fit in or will wobble around.
To learn what size dropper post you need, take out the default seat post and check the reading on it. More often than not, dirt jumpers use 30.9mm or 31.6mm seat posts. The dropper post should match that size.
That said, the above sizes are for dirt jumpers with wide aluminum tubing. Dirt jumpers with steel frames have thinner tubes and in some cases, many need a slimmer dropper post.
Thinner dropper posts are hard to find because the entire dropper post family targets the MTB segment where aluminum and carbon dominate as frame materials.
- Proper Length
The dropper post should be long enough to provide a comfortable pedaling position. This could be problematic because dirt jumpers have small frames and short seat tubes. Consequently, tall riders need a significant rise to sit and pedal comfortably.
To find out how long the dropper post should be, one can use the following guideline:
Extend the current seat post to the point where it allows you to assume a somewhat comfortable position.
This step may require the user to pull the seat post above the point of minimum insertion – a measurement designed to prevent excessive stress on the seat tube and the seat post.
Since the purpose of this procedure is to determine the needed length of the future dropper post, this practice is acceptable and not very dangerous to the seat tube because the bike will not be ridden. The rider would simply sit once or twice.
The next step is to measure the seat post section above the seat collar. The new dropper post has to provide the same height.
To find out whether a dropper post will fit the bill, it’s necessary to do a bit of math.
The total length of the dropper seat post minus the minimum insertion length will have to be equal to or greater than the seat post length needed for comfortable pedaling.
For example, if the total length of the dropper is 530mm and its minimum insertion depth is 150mm, the user is left with 380mm of usable length.
If the required length is within that number, the dropper will elevate the rider sufficiently.
- An Excessively Short and/or Curved Seat Tube
If the bike has a very short and/or curved seat tube, the rider may fail to insert the seat post to the required length. In that scenario, the rider will be unable to lower the seat post as necessary. This problem will be more common for riders with short legs.
- Extra Cables Complicating the Execution of Tricks
Many dirt jumpers come without a front brake because it makes the execution of certain tricks (e.g., bar spins) impossible.
The cable controlling the dropper post will complicate the performance of such stunts too.
This problem can be circumvented by using a dropper post controlled by a lever under the seat. Of course, by going this route, one will be sacrificing comfort and efficiency.
- Unwanted Activation of the Dropper Post
Since dirt jumpers are used for extreme stunts, the rider may activate the dropper post unwillingly.
A similar outcome can be quite dangerous. If the dropper post elevates itself without the rider expecting it to do so, an accident may occur upon landing a trick.
This is one of the reasons why dirt jump riders prefer to keep things simple.
What Are The Advantages of Using a Dropper Seat Post On a Dirt Jumper?
The only reason to install a dropper post is to make the bike more versatile. By lowering the seat, the rider will be able to perform jumps and tricks such as bunny hops and manuals.
By elevating it, the rider will have the opportunity to pedal in a seated position – a luxury that dirt jumpers do not offer by default because they’re designed to be ridden with a slammed seat.
That said, it’s questionable whether this conversion will be very effective because the entire geometry of dirt jumpers makes it difficult to pedal comfortably and efficiently.
Below is a list of characteristics that render dirt jumpers poor commuters and MTBs:
- Excessively short chainstays
- Short wheelbase
- Saddle far behind the bottom bracket (inefficient pedaling)
- Excessively upright position creating lots of drag
- Small frame
- Lack of eyelets for water bottles, fenders…etc.
- Shocks designed to absorb massive landings rather than road irregularities
- Quick-release seat post lever
If you plan on using a dirt jumper for commuting and jumping, the cheapest and simplest solution is to get an extra-long regular seat post (if needed) and a quick-release seat post lever.
Then, you can simply lower the seat post before a session and lift it back for pedaling by opening and closing the quick-release.
Summary: What You Need to Know
- A dropper post can be installed on dirt jumpers when its diameter is compatible with the seat tube in question.
- The rider has to make careful calculations when choosing a dropper post. Otherwise, the unit may fail to provide the height needed for comfortable pedaling.
- A dropper post is an expensive addition to a dirt jumper and offers questionable benefits.
- The cable and housing of a dropper post will complicate the execution of certain tricks.
- The dropper post may be activated unwantedly during riding.
- A cheaper solution is to add a quick-release lever to the bike and use it when switching between dirt jumping and commuting mode.