Dropper Posts - what can go wrong

SeatpostIt has been many years now since the humble gas-hydraulic office chair shrank itself in size and jumped onto its first mountainbike.  Now almost every seatpost, suspension and/or bike company has their own height adjustable “dropper” post.

These vary in appearance, cost and size, but they're all designed to go up and down only when you want them to.  The various designs all have three things: a locking system (hydraulic or mechanical), a spring system (coil spring or compressed gas) and an actuator that can be on the post itself or remotely on your bars.

When they work they're a great asset. Seats go up for the ups and down for the downs. When they don't they're an endless source of frustration. Exactly what can (and does) go wrong depends on the type.

Mechanical (Specialized Command) and Hydraulic Cartridge (Reverb & KS LEV) type posts have sliding parts vented into the frame. Over time and bike washings they end up full of water and dirt instead of clean grease. Some can be easily partially stripped and serviced. Others are built in a way that requires a full strip and service.

Hydraulic bath type posts (X-fusion HiLo & Strate) use the same oil for the hydraulic lock and speed control as lubrication. With use this oil picks up wear particles and needs changed to ensure good life from the seals and sliding parts. Some can also get very slow in the cold. In this case switching to an oil with better cold weather performance makes a huge difference.

If your hydraulic post gets air in the oil it'll turn into an unwanted suspension post. Great for comfort, not so hot for pedalling. If you have a Reverb then you should never, ever, pull up on the seat when the post is lowered. It can suck air into the oil, requiring a full service and oil change to cure.

If the gas pressure in your post drops then it can sink and not come back. Check pressures carefully before trying to pump it back up. Some posts run at very low pressure and even a small gauge amount too much will cause seal failure. You should always find the source of a leak before repressurising and always keep valves capped.

Loss of lock or inability to adjust the post can have many causes - from simple actuator adjustment/bleeding to internal or external leaks. Always check the simple stuff first.

At Shockcraft, as well as suspension, we service and upgrade dropper posts of all types.

Give us a a call if we can help 03-976-7790