Last year, Funn introduced the stealth version of their dropper post, the UpDown. Available in 125mm and 150mm lengths and in 30.9 and 31.6 sizes, the UpDown foregoes the more traditional IFP (internal floating piston) design, which can sometimes suck in air and develop the dreaded sagging seatpost syndrome.
In its place is Funn's "twin-tube cartridge system" which they say mechanically resets and restores oil and air locations within the cartridge during use. This is said to eliminate the saggy saddle issues and create a more reliable and user-friendly system.
Funn UpDown Details
• Travel: 125 or 150mm options
• Self-bleeding twin tube cartridge
• 30.9 or 31.6mm diameter
• Internal cable routing only
• Adjustable remote lever
• Weight: 550g, remote: 50g
• $259 USD - 125mm, $279 USD - 150mm
Funn also include their ultra-adjustable lever with the post. The lever is made to be able to be mounted on the top or bottom of the bars, where its position can be rotated to achieve the desired angle. It's also MatchMaker compatible.
The UpDown looks similar on the outside, but it uses a different design than many other posts currently on the market. The cartridge has an outer and inner tube which contain compressed air and hydraulic oil. When the actuator is in a closed position, the seatpost is locked out and the hydraulic oil contained in the inner chamber supports the rider's weight.
When the actuator opens and dropper compresses, oil flows from the inner chamber to the outer chamber and compressed air enters the upper part of the inner chamber. At full compression, the piston pushes both hydraulic oil and unwanted air from the inner tube.
When the cartridge rebounds from full compression, compressed air pushes the piston shaft upwards and only the hydraulic oil gets sucked into the inner chamber. This way, the cartridge can effectively reallocate both air and oil back to its proper designated locations in the system. This ability to self-restore and refresh theoretically means lower maintenance and no "bobbing" or "sinking" issues with the dropper.
Installing the UpDown was simple, due to the fact that the cable head sits in the dropper post itself while the other end is secured on the lever. This is a great trait in that dialing in cable tension doesn't require pulling the post out of the frame or measuring 17mm to where you secure the cable. Run the cable through the lever, put some tension on it, and you're good to go.
The lever itself is ultra adjustable as mentioned above. The thumb paddle is large, similar in size to that of a SRAM shifter. The action on the lever is much lighter than a Fox Transfer or RockShox Reverb. There is a little bit of play in it, but it's not enough to notice when riding.
When there is weight on the saddle, actuating the post isn't as smooth as I expected. I experienced increased resistance at the lever when sitting with my full weight on the saddle, and there was an almost 'metal-on-metal' grinding feeling at the lever. Easing off some weight made the post actuate more smoothly and with much less force on the lever.
Despite this harshness at the lever, the performance of the post stayed consistent. It doesn't take much force to get the post down and the return speed of the UpDown is moderate, with no fear of the ejection-seat/shotgun style return some other options have.
I reached out to Funn about the lever feel and they replied saying, "Yes, we are aware of this issue. This is due to the cam mechanism design...To alleviate this issue, we suggest to preload the actuator as far as possible. This would help the actuator pass the sideways moving section."
I did as suggested and it alleviated a lot of the tension, but the lever feel still isn't smooth as some of the competition. At the same time, the force required to actually move the seat down once the lever is depressed is quite light, so it's not as if you're ever fighting to get the seat out of the way.
The post's ability to self bleed air out of the system works as advertised. I was able to introduce air into the system by pulling the post up with the bike upside down. This gave a very exaggerated amount of sag in the post with it fully extended, as you can see in the video. With a quick up and down of the post, everything firms back up and is perfectly solid once again.
The ability of the post to automatically "reset" itself as you ride is going to be a big selling point for a lot of riders who have found themselves with IFP issues in the past. In this respect, the UpDown comes out ahead of many of the other posts currently available.Pinkbike's Take