seatpost extension

meb said:

I have a low end folding bike with a 400mm x 25.4 seatpost.
I've damaged and weakened the top of the seattube by riding the setpost
above the insertion line (I've also bowed the seatpost). Therefore I
have to ovecompensate by dropping the tube further down into the
seattube.

Was looking for an interim temp fix for a seatpost extension before
this bike is converted into a folding upright-recumbent redundant (ala
Reynolds Redundant).

Option 1: get a 28-30mm seatpost and outersleve about the old
seatpost.

Option 2: get a 21mm seatpost and inner sleve it within the old
seatpost.

Option 3: Take 3 muffler clamps and juxtapose two seatposts in
overlapping position using 2 claims about both and a 3rd below?

Option 4: Go to Home Depot/Lowes and cut a heavy 25.4 in o.d. pipe to
about 600-700 mm.

Another other options?

Option 4 seems best to me. Although Nitto has one 400mm forged model (
not 25.4 sadly) most longish aluminum posts have a checkered history.
The ability to get adequate insertion is a real plus too.

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

quote='A Muzi'meb said:

I have a low end folding bike with a 400mm x 25.4 seatpost.
I've damaged and weakened the top of the seattube by riding the setpost
above the insertion line (I've also bowed the seatpost). Therefore I
have to ovecompensate by dropping the tube further down into the
seattube.

Was looking for an interim temp fix for a seatpost extension before
this bike is converted into a folding upright-recumbent redundant (ala
Reynolds Redundant).

Option 1: get a 28-30mm seatpost and outersleve about the old
seatpost.

Option 2: get a 21mm seatpost and inner sleve it within the old
seatpost.

Option 3: Take 3 muffler clamps and juxtapose two seatposts in
overlapping position using 2 claims about both and a 3rd below?

Option 4: Go to Home Depot/Lowes and cut a heavy 25.4 in o.d. pipe to
about 600-700 mm.

Another other options?

Option 4 seems best to me. Although Nitto has one 400mm forged model (
not 25.4 sadly) most longish aluminum posts have a checkered history.
The ability to get adequate insertion is a real plus too.

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971[/QUOTE]

The seatpost I have is not aluminum but steel-so while it is bowed, I'm not that concerned with its integritty although there a question how far I can successfully insert it without straightening.

As my 400mm seatpost is way too short, a 400 mm Nitto wouldn't have done any better, I'd need at least 600mm-probably something I'll only find on some other folders (Dahon uses 27.2 aluminum on its long seatpost so its diameter is incompatible; Downtube use 27.2 and 30.4 diameter on their 450mm seatposts).

quote='A Muzi'meb said:

I have a low end folding bike with a 400mm x 25.4 seatpost.
I've damaged and weakened the top of the seattube by riding the setpost
above the insertion line (I've also bowed the seatpost). Therefore I
have to ovecompensate by dropping the tube further down into the
seattube.

Was looking for an interim temp fix for a seatpost extension before
this bike is converted into a folding upright-recumbent redundant (ala
Reynolds Redundant).

Option 1: get a 28-30mm seatpost and outersleve about the old
seatpost.

Option 2: get a 21mm seatpost and inner sleve it within the old
seatpost.

Option 3: Take 3 muffler clamps and juxtapose two seatposts in
overlapping position using 2 claims about both and a 3rd below?

Option 4: Go to Home Depot/Lowes and cut a heavy 25.4 in o.d. pipe to
about 600-700 mm.

Another other options?

Option 4 seems best to me. Although Nitto has one 400mm forged model (
not 25.4 sadly) most longish aluminum posts have a checkered history.
The ability to get adequate insertion is a real plus too.

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971[/QUOTE]

Gave option 4 a try. Thanks.

I was able to get a 24 inch x 7/8 inch O.D. 1/2 inch I.D. galvanized steel pipe and shim it out (although I still need more shimming). With max insert, I have about 150 mm inserted and 450 mm protruding and am about 1 inch higher than preferred, so I'll see if I adapt to the seat height before cutting off a couple of inches. 3/4 I.D. and 1 1/8 O.D. was also available, but I didn't think I could push that into the seattube.

I am experience more oscilation-not sure yet if its play in the shims or flex of the pipe or rear suspension pogoing with the further rear seat position-although I'm now sitting with the suspension travel bottomed out.

The folder is a monotube design with the folding monotube being the only connection between the headtube and cranks. I'm wondering if I ought consider running the cable-lock between the seat and the head tube as a guyline for extra support with this longer seatpost.