longer seatpost needed for a folding bike!



sabinaq

New Member
Feb 15, 2010
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I ride a Boomerange folding bike, and the one thing it doesn't have, is a long enough seatpost for me. I'm tall, with long legs, and have begun to notice knee pain from riding with a seatpost that is too short.
My question is, where can I find a longer seatpost? Because this is a folding bike, the seatpost is already very long, compared with a regular bike. I'm not sure how to look for this online, having already tried and not found much beyond Brompton seatposts which are out of my league, price-wise.
Any suggestions?
Thanks!

Sabina
 

alfeng

Well-Known Member
Jul 23, 2005
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sabinaq said:
I ride a Boomerange folding bike, and the one thing it doesn't have, is a long enough seatpost for me. I'm tall, with long legs, and have begun to notice knee pain from riding with a seatpost that is too short.
My question is, where can I find a longer seatpost? Because this is a folding bike, the seatpost is already very long, compared with a regular bike. I'm not sure how to look for this online, having already tried and not found much beyond Brompton seatposts which are out of my league, price-wise.
Any suggestions?
How long is your current seatpost?

How much longer do you reckon the new seatpost need to be?

What is the seatpost's diameter?
 

sabinaq

New Member
Feb 15, 2010
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alfeng said:
How long is your current seatpost?

How much longer do you reckon the new seatpost need to be?

What is the seatpost's diameter?

Hi, thanks for responding. The current seatpost is 50.5 cm long up to where the diameter reduces so you can put the seat on it. 15 cm are below the limit line, ie 15 cm remain inside the tube of the bike when you raise the seatpost to the limit line. It's diameter is 3 cm.:rolleyes:
Any advice appreciated.
 

alfeng

Well-Known Member
Jul 23, 2005
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sabinaq said:
Hi, thanks for responding. The current seatpost is 50.5 cm long up to where the diameter reduces so you can put the seat on it. 15 cm are below the limit line, ie 15 cm remain inside the tube of the bike when you raise the seatpost to the limit line. It's diameter is 3 cm.:rolleyes:
Any advice appreciated.
You didn't indicate how much longer you needed/wanted the seatpost to be ...

The ideal situation will/(would) be if the current seatpost is STEEL ...

What I would probably try to do is to create an intermediate, telescoping seat tube extension ...

Regardless, with the seatpost that you have, see if the INNER DIAMETER is 25.4mm, or larger ... BUT, not much larger because an alloy seatpost is probably not an ideal structural choice.

If it is, then you can use the existing seatpost as the middle piece ...

You'll need a seatpost collar which will fit over the 30mm (30.9mm? 29.2mm?) seatpost which will become a part of the seat tube ...

AFTER you find a seatpost with a smaller diameter which will sleeve snugly-but-smoothly inside the current seatpost, you would remove the current "cradle" at the top, cut a 5cm expansion/compression slot in the end ... clean the cut edges with a file ...

Insert the original "seatpost" into the frame ...

Install the collar, lube the new seatpost and insert it into the extension, adjust ... VOILA!

FYI. The longest (that I know of) 25.4mm seatpost is 350mm long ... 270mm usable length from the minimum extension line to the cradle.

After subtracting the lost length from truncating your current seatpost, you could add between 8-to-9 inches (20-to-23 cm). If you need MORE than that, then you probably have to get a different folding bike which has a larger frame (e.g., the type that use 26" wheels, or larger).

Presuming you need less than 20 cm more length, leave more of the intermediate section inserted in the frame than not ... and, I would want to have more than the minimum insertion of the seatpost in the extension, too; so, hopefully, you only need about 15 cm more extension.
 

sabinaq

New Member
Feb 15, 2010
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Thanks for this detailed recipe. I will try to follow it. I only need about 5am more height, sorry I forgot to include that in my last post. How is it you know so much about this stuff?
Sabina

alfeng said:
You didn't indicate how much longer you needed/wanted the seatpost to be ...

The ideal situation will/(would) be if the current seatpost is STEEL ...

What I would probably try to do is to create an intermediate, telescoping seat tube extension ...

Regardless, with the seatpost that you have, see if the INNER DIAMETER is 25.4mm, or larger ... BUT, not much larger because an alloy seatpost is probably not an ideal structural choice.

If it is, then you can use the existing seatpost as the middle piece ...

You'll need a seatpost collar which will fit over the 30mm (30.9mm? 29.2mm?) seatpost which will become a part of the seat tube ...

AFTER you find a seatpost with a smaller diameter which will sleeve snugly-but-smoothly inside the current seatpost, you would remove the current "cradle" at the top, cut a 5cm expansion/compression slot in the end ... clean the cut edges with a file ...

Insert the original "seatpost" into the frame ...

Install the collar, lube the new seatpost and insert it into the extension, adjust ... VOILA!

FYI. The longest (that I know of) 25.4mm seatpost is 350mm long ... 270mm usable length from the minimum extension line to the cradle.

After subtracting the lost length from truncating your current seatpost, you could add between 8-to-9 inches (20-to-23 cm). If you need MORE than that, then you probably have to get a different folding bike which has a larger frame (e.g., the type that use 26" wheels, or larger).

Presuming you need less than 20 cm more length, leave more of the intermediate section inserted in the frame than not ... and, I would want to have more than the minimum insertion of the seatpost in the extension, too; so, hopefully, you only need about 15 cm more extension.
 

alfeng

Well-Known Member
Jul 23, 2005
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254
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sabinaq said:
Thanks for this detailed recipe. I will try to follow it. I only need about 5am more height, sorry I forgot to include that in my last post.
Well, I hope the "recipe" is the easiest solution to your immediate problem ...

BTW. A different solution which will add a whopping 3+ kg and about 4+ cm would be to put a HAIRPIN replica saddle on your bike.

BTW2. If you can eschew conventional wisdom, then you can often come up with workable solutions based on other paradigms with which you are already familiar.