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Seatpost for bike

Old 06-27-18, 07:19 AM
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Seatpost for bike


I have a bike that i will do up that is also an ebike but i want to do the mechanic first. It is missing the seatpost and someone paired it with a sawed off seat post that is the wrong size. It says on it 34 but it doesn't go all the way into the insertion line. It also has been cut to make it smaller...which must not have worked. I am trying to find info on the net but so far unsuccessful even on the manufacturers site ENGLISH / E-bike / Folding E-bike_Shenzhen Xidesheng Bicycle Co., Ltd
The bike i have has 14"wheels and none of the ones i can see on this page. I am googling images right now to see if i can find it. The bike was left neglected and is also missing a battery so will work on other stuff then get that sorted after. Plus will try and get more info on the bike itself by looking in the daylight when its not raining(dont worry bike is in a plastic bag all snug). Plus will take photos.
The space inside the shaft where the seatpost goes seems to measure 300mm. I have been looking on sites like aliexpress and ebay . Nothing seems to be available for that size. Just over and just under. Also needs to be long. I really cant spend much as i am on a disability pension and this is just a side project. Can you recommend any sites to buy something?
Also if i got a standard sized seatpost(even tho it does have to be rather long) could this be a solution? https://www.aliexpress.com/item/FETE...4b61ZY73FL&s=p


Last edited by rapattack; 06-29-18 at 03:10 AM.
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Old 06-27-18, 04:04 PM
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shim

Hi. Not really a good solution on a folder as it will possibly come out and get lost when you move the seat up and down.
you could try gluing it in to the frame as an insert.
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Old 06-27-18, 11:54 PM
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"Standard sized" ?








...

Last edited by fietsbob; 06-29-18 at 10:34 AM. Reason: why are so many people allergic to measuring ?
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Old 06-28-18, 08:23 AM
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Originally Posted by bhkyte View Post
Hi. Not really a good solution on a folder as it will possibly come out and get lost when you move the seat up and down.
you could try gluing it in to the frame as an insert.
Oh thanks good to know what the options are
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Old 06-28-18, 08:24 AM
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Originally Posted by fietsbob View Post
"Standard sized" ?
I dont know really what standard sized is but most bikes i see around have the same sized seat post...i am not talking about foldies ...just most bikes
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Old 06-28-18, 12:56 PM
  #6  
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Why don't you contact the manufacturer/vendor to get the specs on the seatpost, and ask if you can get a replacement.

It is hard to tell from your description. For standard vintage steel frames, using an oversized seatpost will sometimes stretch the clamp, and allow the seatpost to go in an inch or so before stopping, or jamming it in further can cause rippling of the tubes.

Most folding bikes I've seen allow the posts to go up and down very easily. Does the seatpost hole go all the way through to the bottom? You should be able to measure the bottom end of the hole, hoping it hasn't been deformed.
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Old 06-29-18, 12:42 AM
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Originally Posted by CliffordK View Post
Why don't you contact the manufacturer/vendor to get the specs on the seatpost, and ask if you can get a replacement.

It is hard to tell from your description. For standard vintage steel frames, using an oversized seatpost will sometimes stretch the clamp, and allow the seatpost to go in an inch or so before stopping, or jamming it in further can cause rippling of the tubes.

Most folding bikes I've seen allow the posts to go up and down very easily. Does the seatpost hole go all the way through to the bottom? You should be able to measure the bottom end of the hole, hoping it hasn't been deformed.
This was something found in a council cleanup. I looked at the manufacturers website and the bicycle is not listed there. So maybe not made anymore. I could try if i can find a model name or name on it. Good point. yes dont want to do more damage. Oh thanks your right.

Last edited by rapattack; 06-29-18 at 03:11 AM.
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Old 06-29-18, 03:13 AM
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I have contacted the manufacturers website in australia. There is no model number but there is a serial number. I dont know if the serial number is to ID the bike or means what model it is. The seatpost could go thru to the bottom as per the photo i uploaded on the original post. Theres also a photo of the bike. I have plenty of other photos if needed
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Old 06-29-18, 10:32 AM
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Seat tube OD minus 2x tube wall thickness ( another variable ) gives you the tube ID, the seat tube ID is what remains.. a thick wall tube with a 9/8" OD can have a small diameter seat post ..

A thin wall seat tube of same OD , can take a larger seat post ..
Or a seat post sizing shim sleeve to use a smaller seat post

For example a telescoping seat post (a Brompton option)

has a smaller seatpost inside a larger one and that larger one fits in the frame..
it has 2 QR you open to fold it , so a longer one fits ,when folded, to not protrude
any further than the shorter standard one
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Old 06-29-18, 10:41 AM
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Buy a set of calipers with an LCD screen .. China makes those Too. measure ..?
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Old 06-30-18, 02:57 PM
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Folding bike seat posts are longer than regular bikes. You probably need something that is 600mm (almost 24") long. The seat tubes in my Downtube folders (I was just measuring them today) are 30.3mm and over 22" long.

If I used an insert, I'd want one by the clamp and the other one with the lip removed so it can go down in the tube. I'd glue it to the bottom of the tube too. I am using an insert on one of my bikes, but the tube is only 8" long and only a few inches are above the frame. With a folder, you might have a foot or more above the frame and you don't want the bottom free to move.
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Old 07-01-18, 07:25 AM
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Originally Posted by fietsbob View Post
Seat tube OD minus 2x tube wall thickness ( another variable ) gives you the tube ID, the seat tube ID is what remains.. a thick wall tube with a 9/8" OD can have a small diameter seat post ..

A thin wall seat tube of same OD , can take a larger seat post ..
Or a seat post sizing shim sleeve to use a smaller seat post

For example a telescoping seat post (a Brompton option)

has a smaller seatpost inside a larger one and that larger one fits in the frame..
it has 2 QR you open to fold it , so a longer one fits ,when folded, to not protrude
any further than the shorter standard one
Whats an OD? I have seen bromptons around. What is a QR?
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Old 07-01-18, 07:26 AM
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Originally Posted by fietsbob View Post
Buy a set of calipers with an LCD screen .. China makes those Too. measure ..?
I might not have to as a bike mechanic is coming over in a few days to change the rusty chain...or put a new one on...so can ask him to measure for me
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Old 07-01-18, 07:28 AM
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Originally Posted by Doc_Wui View Post
Folding bike seat posts are longer than regular bikes. You probably need something that is 600mm (almost 24") long. The seat tubes in my Downtube folders (I was just measuring them today) are 30.3mm and over 22" long.

If I used an insert, I'd want one by the clamp and the other one with the lip removed so it can go down in the tube. I'd glue it to the bottom of the tube too. I am using an insert on one of my bikes, but the tube is only 8" long and only a few inches are above the frame. With a folder, you might have a foot or more above the frame and you don't want the bottom free to move.
Yes i sort of figured that one out. Thanks thats more accurate than i was thinking as per length. Oh not sure what you mean about the rest but i am getting a bike mechanic to come around in a few days to change the chain. I will find out this stuff at the same time
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Old 07-01-18, 08:56 AM
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Originally Posted by rapattack View Post
Whats an OD? What is a QR?
Pretty universal; Outside diameter. and quick release..
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Old 07-01-18, 09:06 AM
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Originally Posted by fietsbob View Post
Pretty universal; Outside diameter. and quick release..
Oh outside diameter yeah that i know thanks....oh i am a bit lost now. I will give up on the thing that i mentioned i was thinking about getting to make a so called standard fit. Will just wait til i talk with the bike mechanic in a few days
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Old 07-01-18, 09:16 AM
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Years ago , for a post that had to be 1" (25.4mm), & extend out 12" ,
I got a Chrome plated Chromoly seat post
and a saddle clip for the top ( straight tube type post , top reduced to 7/8")

Was from US importer; Seattle bike supply... "Redline" brand ..












0
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Old 07-01-18, 09:19 AM
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Originally Posted by fietsbob View Post
Years ago , for a post that had to be 1" (25.4mm), & extend out 12" , I got a Chrome plated Chromoly seat post
and a saddle clip for the top ( straight tube type post , top reduced to 7/8")

Was from US importer; Seattle bike supply... "Redline" brand ..












0
You have really lost me here ummmm...oh and in australia we do metric...
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Old 07-01-18, 09:33 AM
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.... but commonly steel & other, tube is imperial diameters so bike frames express 1.125" as 28.6mm,
1.25" is 31.75 and so rounding up, said as 31.8..
And as you should have memorized; as a conversion factor 1 inch is 25.4mm

Example: Brompton used imperial tube for their seat posts , plastic bushing in frame ..

many seat posts are a result of frame tube wall thickness differences
resulting in various inside diameters ...

Math..


...
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Old 07-28-18, 08:48 AM
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OK sorry i didnt get notified there was a response...odd no email. OK yeah i think i might have estimated 31mm but i am going to wait for bike mechanic as he will have calipers and we had to look at something else anyway. I had buying things i wont probably use again but thanks for your help
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Old 07-28-18, 12:26 PM
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I use my Calipers even to buy Guitar strings,, I measure what I use now,
and go shopping..

they're cheap , as are tape measures . both, together,

sell for about what you pay monthly for the I-Phone bill.
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Old 08-16-18, 09:51 AM
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Originally Posted by fietsbob View Post
I use my Calipers even to buy Guitar strings,, I measure what I use now,
and go shopping..

they're cheap , as are tape measures . both, together,

sell for about what you pay monthly for the I-Phone bill.
yeah dont need it...which reminds me that bike guy still hasnt been over...have to leave him a message
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Old 10-07-18, 06:59 AM
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So i have had a real pain of a time trying to get this seatpost after the bike mechanic check the size. He said the width is 34mm so i bought the closest to that available which is 33.9mm. The first order came and they sent me 31.9mm then a different seller again 31.9. I told the second seller beforehand to double check so they dont make a mistake. And you want a long time before the item comes from china to australia. so this is the one i have ordered yesterday https://www.aliexpress.com/item/Bicy...a9f94c4dj11VLo ....fingers crossed he he
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Old 10-07-18, 08:07 AM
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Most newer Dahons come with 33.9 seat posts. Roger
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Old 10-07-18, 08:13 AM
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Originally Posted by rhenning View Post
Most newer Dahons come with 33.9 seat posts. Roger
Oh ok. I dont have that brand. I forgot this brand name
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