I’ve had my Dahon MU to about nine months and have really gotten to know the bike. One feature I really like, enjoy, even treasure is the seat post pump. It really does operate like a floor pump. But there is/was a problem. Over the last few months it has been getting harder and harder to push the rubber hose back inside the seat post/pump shaft before clamping the post back into the bike frame. In the last week I’ve had to grab the hose with needle nose pliers while twisting and pushing with considerable force to break the hose free from it’s inflation position. In frustration I finally cut the hose just beyond the brass hose bib and reinserted the “fresh” hose end over the bib and voila it works like new.

The rubber hose is pretty long so I suppose I will be able make this fix a number of times, but did I do anything to cause the problem and have others experienced the problem? The only thing that comes to my mind is that I lubed the pump with a wet chain lube and maybe this caused the hose to swell or become sticky. Any ideas?

Not sure. My Dahoon Curve has the same pump. I am not using it much, I am kind of saving it for a rainy day.

For sure oil can be a killer for rubber. I remember in the 90`s when they started experementing running diesel engins on Canola oil. A person told me the only thing you had to change in the engine was the rubber fuel hoses becouse the ones that came with the car could not take the contact with the oil.

"Swelling" is what happends to the rubber when in contact with the wrong oil.

I also somewhere have a tiny bottle of oil ment for bike pumps to avoid destroying the gasket with the wrong oil. Not sure if the gasket was rubber or leather in the old pumps.

A recent thread on these forums recommended silicone grease for pump maintenance. I have used common grease for years and not had a problem. Apparently though certain greases can cause the type of issues discussed here. The silicone, I was told will not react with the rubber/synthetic components and is always a safest bet.

I bought it and plan to get some silicone grease.

I have 3 different biologic post pumps. Two first gen that had a different hose material (orange), that deteriorated. The newer of the 3 is similar to yours but has gotten basically no use what so ever. It is slightly used bike that gets topped off with a floor pump and had not the symptoms and has never needed maintenance.

The two older pumps I recently serviced, they are in need of new hoses (not the same issue as yours). I picked these up second hand and they had been neglected.

Is this what were talking about?

Quite honestly I had no idea what kind of silicone grease to buy or use.

The PDF MSDS here: https://www.w8ji.com/images/Cars/Battery/09980.pdf

It appears from this document and reading Wikipedia that this would be an excellent choice for our intended purpose.

Tks for posting.

Has any one found a source for biologic post pump parts? I am going to need a new hose soon.
The model I have uses crimped on fittings on the upper end.

Sorry to necro this , but just bought two used bikes that need this I am trying : Biologic at thinkbiologic.com

and will follow up if they respond to the ContactUs

Try ThorUSA.com

I've got one I took off my Mu Uno. Works great, even has the black plastic end piece. DM if you want to buy it, happy to sell and ship. $20 plus actually packing/shipping cost.

Did , not in stock with Thor [MENTION=375764]linberl[/MENTION]
I have a post in to Biologics in Taiwan and will give you a follow up with what their reply.
That cap is important on the 34mm seatpost, if it comes off at teh wrong time all kinds of mischief may ensue

I just found it made the bike heavy and I already own CO2 as well as a super tiny mini pump, so I replaced the Biologic with a Litepro seatpost. So the pump post is just
hanging around here, along with the Aria bike saddle that came with my Mu Uno. My posterior prefers a particular Fizik saddle, and you always make sure your rear end
is happy, lol.

Hmmm,...maybe I should take you up on your offer,...

Lolz. Let me know.

Available on Tern's website.

https://buy.ternbicycles.com/collect...p-2-0-seatpost

My seatpost pump from 2010 died around 2015. When attached to an inflated tire, the pump stick would simply extend all the way and the pressure was so high that I couldn't pump. I assume that a rubber seal has probably failed. I couldn't figure out how to open it to take a look, so I went for a thudbuster instead, and changed to Schwalbe tires with greenguard, and haven't had a puncture since. I bought a tiny topeak handpump to carry with me on trips but never used it.

In practical terms I use a floor pump before I ride.
Versus my usual tool roll , used to across my multiple bikes, I find a small lightweight portable pump more to my purpose.
The seat post pump is not particularly heavy but still lacks increased utility.
Repairing an unused damaged pump is not attractive.
Does anyone actually use these things?