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Tern link A7 - Titanium seatpost or suspension?

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Tern link A7 - Titanium seatpost or suspension?

Old 04-09-19, 07:52 AM
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Mcarto
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Tern link A7 - Titanium seatpost or suspension?

Hi, a few weeks ago I bought Tern Link A7. I chose a basic bike because don't have good knowledge of folding bike. Tern is famous/popular company has a solid frame so seems is a good base for modification.

I'm quite happy with my bike but want a better suspension for the comfort of the ride.

Read this forum and similar many times, change my saddle for Brooks with is much better, consider change tire for Big Ben? but actually, Kenda is not so bad and rolling nice.

Think about titanium seatpost or Biologic Tern suspension. Many users too recommended telescopic post due to easy adjustment and collecting saddle from the street... so may is a good idea get the telescopic post and change upper part 27.2mm for any cheaper suspension seatpost from a classic bike?

I'm 187cm tall and 83 kg weight, original seatpost (580mm) is enough long for me - I still have 1-2 cm extra. I have due to age (40+) returning small problems with knee so need a possible more healthy option.

The bike is using for trekking, off-road riding, better exploration of visited cities/places. Don't have plans hard/sport ride.


Won't spend more than 70 euro for it, still need rack, pedals...
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Old 04-09-19, 02:54 PM
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fietsbob
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probably no much at your price maximum

look for a saddle with springs in it ?

pay what they ask (IDK what things cost in the EEC market including VAT. )

There are cheap suspension seat posts, and there are good ones that are not cheap.
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Old 04-10-19, 06:18 AM
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Originally Posted by fietsbob View Post
probably no much at your price maximum

look for a saddle with springs in it ?

pay what they ask (IDK what things cost in the EEC market including VAT. )

There are cheap suspension seat posts, and there are good ones that are not cheap.
Thx
Actually I just consider suspension, newer had any bike with it so I not sure. It is my first bike from a long break, my first ride on very well pump tires was as medieval torture.
I lowered air pressure, bought recommended Brooks saddle and is much better. The new saddle is very good and every week seem more comfortable.

May I just change tires for Big Ben (Big Apple) for better off-road, curbs ride? Many persons recommended it but I want to resign from good rolling?
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Old 04-11-19, 03:37 AM
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I made myself a telescopic seatpost from aluminum pipe with 2mm wall thickness. Basically some sort of extension of bike seat tube with another seat clamp at the top and frame seat tube clamp at the bottom. Then I inserted into it a normal suspension seatpost for regular bikes. I used Suntour SP NCX 12 which I consider better than ordinary seatpost suspension that you can find for folding bikes, such as Biologic. This Suntour suspension is so good I have it on my four bikes. It has proven itself as very reliable over many years of riding. It works great on both folding 20 inch bike and my touring all terrain bike.
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Old 04-11-19, 03:40 AM
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If anyone's interested in this mod, I documented it with photos step by step, unfortunately still don't have 10 posts to post photos.
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Old 04-12-19, 06:50 AM
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Originally Posted by Indigo82 View Post
If anyone's interested in this mod, I documented it with photos step by step, unfortunately still don't have 10 posts to post photos.
Make one more post describing the step by step process and then add pictures immediately in your next post. I'd be very interested in seeing how you accomplished this modification.
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Old 04-12-19, 12:41 PM
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pretty simple: slot a tube lengthways much like they do in the frames, say an inch long ,
to make it compressible.
stop drill at the slot bottom round, to resist further splitting

get a seat tube binder clamp band .. that fits over the tube end to squeeze it..

If ID is not a typical seat post size, like 27.2 or 25.4, there are machined shim sleeves to make it so..




...




...
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Old 04-13-19, 02:28 AM
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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.



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Old 04-13-19, 06:17 AM
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Good idea!
Just one question if I'll find thinner adapter/insert then is not necessary to reduce the diameter of the tube? Any craftsman will make it from a piece of sheet metal but can be too thin - may use steel instead of aluminum?
Some information about the tube? cannot find similar with 2mm wall thickness.
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Old 04-13-19, 09:09 AM
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Let's assume that you need 33.9mm diameter seatpost for your bike since Biologic suspension seatpost for Tern bikes comes in exactly the same size. In case you opt for regular suspension of 31.8mm, that leaves you with only around 1mm wall thickness for seat extension which is not enough. Therefore you will need 27.2mm regular suspension seatpost diameter like I had in my first example. Now, you probably need to make or buy aluminum or steel shim (reducer, insert) for the bike seat tube to reduce the opening from 33.9mm to the first available aluminum pipe size that will have wall thickness of 1.5mm and above. As I mentioned in my example number one, I had shim from 33.9mm to 31.8mm, but then had to sandpaper pipe from 32mm to 31.8mm (outer diameter of my new extension became 31.8mm after sandpapering and inner is 28mm due to wall thickness of 2mm; 28mm is fine to accept 27.2mm seatpost if you thighten it properly; clamp doesn't have too be quick release as you already have another clamp at the original frame; it would be even possible to put one layer of tape over regular seatpost before finally inserting into extension so that everything become more tight). Sandpapering 600mm pipe by hand for just 0.2mm is not fun for that length. There is lot of metal in those 0.2mm and you have to check tolerance all the time. So, as you suggested, finding a machinist to make you a custom shim from 33.9mm to the next available aluminum pipe size (in my case 32mm with 2mm wall thickness) would work without any sandpapering.

Basically, you need 33.9mm to 32mm custom made shim (this can be even made from aluminum sheet), 600mm of aluminum tube - 32mm outer diameter with 2mm wall thickness and regular suspension seatpost with 27.2mm including a new seat clamp.

Now, price of Biologic telescopic seat post is around 45$ whereas Suntour is 116$ plus aluminum pipe (cheap), plus custom shim (can be free if you have a friend machinist), plus seat clamp (cheap). You can see that original Biologic is less expensive. So it's up to you to see what you prefer. I had two spare new Suntour suspensions that I didn't use so I modified and used them in folding bikes. I also prefer design and action of Suntour to Biologic.

Well, regarding tubing, I checked on the Internet now but it seems all is in inches, so I searched aluminum tubing in millimeters and found this site https://www.metricmetal.com/product/...und-tube-6060/

Last edited by Indigo82; 04-13-19 at 09:18 AM.
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Old 04-13-19, 09:32 AM
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Now I see that in Germany, Suntour costs around 50 euros (in case you're somewhere there). But now I see that for 60$ you have telescopic seatpost for Tern where you can insert 27.2mm regular seatpost, so why bother making all this what I described.
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Old 04-14-19, 09:34 AM
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Originally Posted by Indigo82 View Post
Now I see that in Germany, Suntour costs around 50 euros (in case you're somewhere there). But now I see that for 60$ you have telescopic seatpost for Tern where you can insert 27.2mm regular seatpost, so why bother making all this what I described.
It makes sense, you still save some money and the longer tube gives you the options for customizing seatpost.
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Old 04-18-19, 06:28 PM
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You can get a ti post on aliexpress for about $80. It's Brompton diameter, maybe smaller than your Tern, in which case you would have to use a shim.
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