Hello all, maybe this will help someone with the same trouble as me. Well, it's not a trouble anymore. And I didn't make complete suspension but an extension of it. I had Suntour NCX SP 12 suspension seat post at a diameter of 27.2mm and length of 300mm which was both not good for my folding bike, the first being too small, the second being too short. My folding bike had aluminum insert in the seat tube making it 31.8mm for the original non-suspended seat post, and I guess the seat tube without the insert was 33.9mm.






Length of the seat post is 550mm. I found aluminum tube made from 6060 alloy, external diameter 32mm and internal diameter 28mm, i.e. wall thickness 2mm. Then I cut it to 550mm in length and had to reduce outer diameter from 32mm to 31.8mm by sandpapering it. This was not so easy to do really as it may seem to be.



Once the cutting by hacksaw in the new tube was done to make 30mm long and 4mm wide groove, original NCX SP 12 was inserted to the new tube and I had to use seat post clamp for 32mm seat tube to fasten the NCX SP 12.





Finally, the complete set was inserted in the bike and I gave it a test ride. All was fine. I was little bit scared if the 2mm thickens of the tube would survive but so far so good even though I have reduced it 31.8mm. I am not a heavy guy and that should be factored as well. In the end, I painted the seat post in black to match the color of my bike. I could've bought a new suspension seat post for folding bike but they were either not available in the diameter of my frame seat tube or more expensive than the materials used to make it. Besides, NCX SP 12 is not made in 550mm length and I consider it a great suspension which I have on two other mountain bikes. Also I couldn't find a factory made extension seat post in those diameters. But I must say I had a spare Suntour NCX SP 12 suspension which reduces the price of the complete endeavor though. Thanks and regards, Peter.



After making sure this mod is successful, I made another one to the other bike I have. It already had telescopic suspension seatpost but I didn't like it very much. I prefer parallelogram seatpost like the SP 12 NCX. Here the seatpost had 35mm diameter so it was much easier to choose aluminum pipe of the same diameter as it comes as a standard. Here instead of 2mm wall thickness it came with 1.5mm wall thickness which was OK considering that the whole pipe is of bigger diameter. Aluminum grade is 6060. With 1.5mm wall thickness the internal diameter came to 32mm which was fine for NCX that had 31.8 diameter, different than on the previous bike. Since the original was also silver, there was no need to paint it later on, just to cut the desired length and make a groove just like on ordinary bike seat tube so that the seat clamp can tighten the insert, i.e. suspension seatpost for normal bikes. And here the clamp was for 35mm seat tube. Before and after the mod photos are shown. If you wonder which brand of bike is the second one, that is German made Cyco. Not an expensive bike, rather cheap, but proved as a really nice bike. So, all in all I was happy to have SP NCX suspension on my folders just as I have it on my other bikes. It's not produced for folders but it can be adapted quite easily.