Few technological advancements have impacted the sport of mountain biking as significantly as dropper seatposts. Riding position is crucial for tackling any type of trail or feature – a dropper post ensures you’re always able to achieve that perfect position to ride better, faster, and safer.
But like any technology, sometimes your dropper post will refuse to drop…or go up…or generally do what it’s supposed to do. Sure, it’s frustrating to be suddenly thrown back into the Stone Age – when riders had to actually get off their bikes and adjust the seatpost height by hand. Can you even imagine??
But every problem has a solution. When it comes to dropper posts, many fixes can be done right in your own garage. Here are four of the most common problems you may encounter, along with some solutions that should get you back on the trail in no time.
1. Dropper Post Sinking Down
A dropper post is actuated by a lever mounted on the handlebars. In an extended position, a dropper post shouldn’t sink down just by sitting on it. If it does, there are three potential problems: two are easy fixes; one is better left to a professional bike mechanic.
First, if the dropper post lever won’t disengage fully after being pushed, it will continue to put tension on the cable, allowing the post to sink down under your weight.
Second, the dropper post may not have enough air pressure for your weight. Yep, while they’re mechanically actuated via a lever and cable, dropper posts are also pressurized. This allows them to shoot up when the lever is pressed. Just as your suspension and tires will feel squishy when air pressure is too low, your seatpost will sag if it isn’t set up for your weight.
Third, it’s possible that air got past the post’s internal seals, causing the same problem you would experience if air bubbles formed in your hydraulic brake lines. This is generally caused by hanging or picking your bike up by the saddle when the seatpost is down. DON’T DO THIS!!!
How to Fix It
If your dropper lever won’t stay closed, check that the cable tension isn’t too high or low. Either could prevent the lever from returning to the closed position after being pushed. Find the barrel adjuster (the rotating plastic piece that sits where the cable feeds into the lever). Try turning it in both directions and engaging the dropper post lever to see if it makes a difference.
If cable tension is correct, but the lever still won’t stay closed, it could be damaged and may need to be replaced. Just like brake levers, a dropper post lever is very vulnerable to damage if you crash.
Adding air to a dropper post is easy: with the post extended, remove the saddle from the rails and use a high-pressure shock pump (NOT a tire pump) to add 10-15 psi at a time before replacing the saddle and seeing if it solves the problem. Check the manufacturer’s website first to make sure you don’t exceed the maximum air pressure settings for your post!
If air has intruded past the internal seals, you’ll have to take your bike to a mechanic so the air can be bled out of the post. This should fix the spongy feeling you get when sitting on your saddle.
2. Dropper Post Stuck (Won’t Go Up or Down)
So, your post refuses to move no matter what you do. Well, before you go nuts taking your bike apart, check the seatpost clamp first. If it’s too tight, it could be squeezing your post enough to prevent it from working properly.
Internally, your dropper post cable could be corroded or damaged. This could prevent it from moving through its housing when the lever is pushed.
There may also be too much excess cable length: the cable may move when the lever is pushed, but all that slack prevents it from actually doing anything.
How to Fix It
Tackle the seatpost clamp first. Loosen the bolt, pull out the dropper post and visually inspect it for any damage. If it looks good, replace it and then use a torque wrench (if you have one) to tighten the clamp to the listed specification. No torque wrench? That’s ok: just tighten the clamp enough so it holds your weight without moving around…and no more.
To check on the state of your cable, you’ll need to detach it from the dropper post. Loosen the seat post clamp and pull the dropper post out of the seat tube. Detach the cable from the bottom of the post, then pull it through the bike frame from where it attaches to the lever. If the cable looks rusty, kinked, or otherwise damaged, it should be replaced.
If there seems to be an excessive amount of cable stuffed into the frame, you should trim it down (from the lever side) so it will work more effectively. Before you trim, make sure to measure with the seatpost up: you don’t want to cut it so short that it prevents the seatpost from moving up all the way!
3. Dropper Post Won’t Go All the Way Up
Once again, the seatpost clamp could be the issue. If it’s too tight, it can prevent the dropper post from moving all the way through its travel.
A kinked cable could also be to blame, as it would inhibit the post from reaching the top end of its travel (kinda like what would happen if you cut the cable too short!)
How to Fix It
Similar to the problem above, check the easiest solution first before you deal with the frustration of routing cables through your bike frame! Loosen the seatpost clamp and retighten it to the proper torque.
If that doesn’t do it, follow the steps above to thread the dropper post cable through the frame. If it’s kinked or damaged in any way, it’s best to replace it.
I also found the below video related to this problem, and thought you might find it helpful:
4. Dropper Post Wiggles
Before you panic and think your seatpost is gonna spin all the way around while you’re riding, know this: a little bit of wiggle is ok! Actually, it’s built like that for a reason.
No matter how careful you are, dirt will inevitably find its way down into the seatpost. The little bit of space between the seatpost and seat tube gives the dirt room to hang out between cleanings. Without that wiggle room, dirt and grim would be squeezed against the post and tube, scratching and damaging both.
There shouldn’t be more than about 2 mm of lateral play, however. For an easy way to measure, check out this article from PNW Components. It provides a lot of great information when troubleshooting common dropper post issues.
How to Fix It
If there is too much lateral play in your dropper post, it will probably need to be rebuilt or replaced. Unfortunately, this is one issue that is best handled by a professional.
Dropper Post Maintenance Tips
To prevent potential issues, follow these general cleaning guidelines after every ride:
- With dropper post lowered, unscrew threaded mid cap and slide it up seatpost
- Extend post to drive dirt up from underneath seals
- Wipe dirt away with a clean cloth
Once every few months, apply a few drops of a suspension lubricant (like Forkboost) to the seal and compress the post a few times to distribute the lubricant. For more general maintenance and cleaning tips, read this.
And remember not to hang or pick up your bike by the saddle with the seatpost compressed!
What Goes Up, Should Come Down…and Vice Versa
Dropper posts require regular maintenance, just like the rest of your bike. Luckily many of the issues that may arise are simple fixes, but following the general cleaning and maintenance tips above goes a long way to preventing these issues in the first place!
Unless you want to go back to the days of manually adjusting your seat height before every steep climb or descent. That’s so last decade.