27.4 seat posts?

Road Man said:

For my Trek 610, I want to try a larger seat post. The original SR
Laprade is 27.2, but it feels loose, and the integral seatpost tabs
converge when I tighted the binder bolt. I tried an old 2-bolt Campy
27.2, and it is a bit larger, but still loose. Adding .001 brass shim
stock helps. I'd like to try a 27.4 mm post, but I can't find any on
websites or the big sellers. Anyone have one to sell?

I really like the old Campy 2-bolt, cosmetics are not important!

Ken Freeman

Any LBS can get you a 27.4 post. It'll be a somewhat basic but
reasonable quality one and cost $15-20. You're not likely to find one
on the net for that price including shipping. However, if a 27.2 fits
well enough that it could ever be tightened securely enough to ride,
than most likely a 27.4 isn't going to fit at all. I'd have someone who
knows the ins and outs of babying frames having these kinds of problems
and has access to seattube honing stuff give yours a look over.

Road Man said:

For my Trek 610, I want to try a larger seat post. The original SR
Laprade is 27.2, but it feels loose, and the integral seatpost tabs
converge when I tighted the binder bolt. I tried an old 2-bolt Campy
27.2, and it is a bit larger, but still loose. Adding .001 brass shim
stock helps. I'd like to try a 27.4 mm post, but I can't find any on
websites or the big sellers. Anyone have one to sell?

I really like the old Campy 2-bolt, cosmetics are not important!

Ken Freeman

American Classic makes a 27.4 seatpost. Kalloy does too. And a few
others. Waterford used 27.4 seatposts on its higher up road racing
frames until just a few years ago. For checking on the internet, go
over to the Harris Cyclery website and get into their QBP listings.
They should show 27.4 seatposts.

Road Man said:

For my Trek 610, I want to try a larger seat post. The original SR
Laprade is 27.2, but it feels loose, and the integral seatpost tabs
converge when I tighted the binder bolt. I tried an old 2-bolt Campy
27.2, and it is a bit larger, but still loose. Adding .001 brass shim
stock helps. I'd like to try a 27.4 mm post, but I can't find any on
websites or the big sellers. Anyone have one to sell?

I really like the old Campy 2-bolt, cosmetics are not important!

Ken Freeman

We sell 27.4 SP but have a bike shop knurl the old post a bit. It will
take up that slack...

I used a 27.4 post in my Surly LHT when a 27.2 felt rather loose when
inserted. I just got a fairly cheap Kalloy post through my LBS.

Nick

"Road Man" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

For my Trek 610, I want to try a larger seat post. The original SR
Laprade is 27.2, but it feels loose, and the integral seatpost tabs
converge when I tighted the binder bolt. I tried an old 2-bolt Campy
27.2, and it is a bit larger, but still loose. Adding .001 brass shim
stock helps. I'd like to try a 27.4 mm post, but I can't find any on
websites or the big sellers. Anyone have one to sell?

Road Man said:

For my Trek 610, I want to try a larger seat post. The original SR
Laprade is 27.2, but it feels loose, and the integral seatpost tabs
converge when I tighted the binder bolt. I tried an old 2-bolt Campy
27.2, and it is a bit larger, but still loose. Adding .001 brass shim
stock helps. I'd like to try a 27.4 mm post, but I can't find any on
websites or the big sellers. Anyone have one to sell?

I really like the old Campy 2-bolt, cosmetics are not important!

Campy has made 27.4 posts since forever, in both one and two bolt models.

But I'm surprised your Trek doesn't like the 27.2, since that's how it
left the factory. The only 27.4mm Treks were the model 170 (limited
production, Reynolds 753 frame).

--

John "old Trek worker" ([email hidden])

Road Man said:

For my Trek 610, I want to try a larger seat post. The original SR
Laprade is 27.2, but it feels loose, and the integral seatpost tabs
converge when I tighted the binder bolt. I tried an old 2-bolt Campy
27.2, and it is a bit larger, but still loose. Adding .001 brass shim
stock helps. I'd like to try a 27.4 mm post, but I can't find any on
websites or the big sellers. Anyone have one to sell?

I really like the old Campy 2-bolt, cosmetics are not important!

That frame has a notoriously narrow slit in the seat lug.
Cut it wider, lube the integrated allen bolt well and you
should be OK.

Going from a 27.2 post to a 27.4 post is a _huge_
difference. Contemplate the law of unintended consequences

for a
moment and then don't do that! A good test is to slip the
post in all the way. It should have no side play at all yet
still move in and out easily in a clean seat tube. Your Trek
will likely pass that test at 27.2mm.

You might also try a micrometer on a few posts. Some will be
big and some small. Knurling a smallish post is a
reasonable solution if it is still loose after you clean up
the seat lug.

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

I have several 27.2's, and all slip loosely. They do not all mike the
same, I've checked. The original post has always been a loose fit.
It would only tighten when the binder bolt tabs were touching. Sad to
say, I think this a design flaw in an otherwise great bike. One of
the binder bolt tabs broke off, and Trek repaired the frame on
warrantee. I have had one or two long-time Trek dealers tell me nasty
anecdotes about factory problems at Trek. Still, this is a great bike
now that I'm getting it sorted out. The 73 degree seat tube suits my
legs very well.

Tony Oliver says in "Touring bikes" that 531 has clearance for 27.4
posts when they are brazed at low temperature. Trek advertized
low-temp braze in its 1984 brochures, and in the earlier brochures
called out silver braze. Perhaps I shouldn't be surprised that 27.2's
are sorta loose.

My thickest 27.2 fits well with a .001 brass sheet wrapped around it.
I guess I'll have an LBS check the ID with a guage before pulling the
trigger on a 27.4 post. Knurling sounds like a good thing to try on
the Laprade.

Thanks for all your input!!

Ken

"A Muzi" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Road Man said:

For my Trek 610, I want to try a larger seat post. The original SR
Laprade is 27.2, but it feels loose, and the integral seatpost tabs
converge when I tighted the binder bolt. I tried an old 2-bolt
Campy 27.2, and it is a bit larger, but still loose. Adding .001
brass shim stock helps. I'd like to try a 27.4 mm post, but I
can't find any on websites or the big sellers. Anyone have one to
sell?

I really like the old Campy 2-bolt, cosmetics are not important!

That frame has a notoriously narrow slit in the seat lug. Cut it
wider, lube the integrated allen bolt well and you should be OK.

Going from a 27.2 post to a 27.4 post is a _huge_ difference.
Contemplate the law of unintended consequences

for a moment
and then don't do that! A good test is to slip the post in all the
way. It should have no side play at all yet still move in and out
easily in a clean seat tube. Your Trek will likely pass that test at
27.2mm.

You might also try a micrometer on a few posts. Some will be big and
some small. Knurling a smallish post is a reasonable solution if it
is still loose after you clean up the seat lug.

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

"Road Man" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

My thickest 27.2 fits well with a .001 brass sheet wrapped around it.
I guess I'll have an LBS check the ID with a guage before pulling the
trigger on a 27.4 post. Knurling sounds like a good thing to try on
the Laprade.

I assume you mean a .1 brass sheet, otherwise you are maiking a 27.2 into a
27.202.

Anneal the edge of the sheet, cut some 3mm slits in the edge, and bend them
over. Voila, a seatpost shim. Go ride the bike.

The brass sheet is .001 inches wrapped in a complete circle, so adding
..002 inches to the seatpost OD. The Campy post that's in place
measures
1.069 inches (equals 27.15 mm), for a total or 1.071 inches built-up
diameter,
not accounting for grease. Multiply by 25.4 mm per inch, and the
built-up
diameter is 27.20 mm.

So a 27.4 nominal seatpost should (if similar) measure about 27.3 to
27.35,
meaning it might be too tight. I don't know the ID of my seatpost,
I need to have a good LBS test the seatpost with one of those slip-in
guages if they have one.

This probably also means the 0.1 mm brass sheet will be too big.

Thanks to all for the help and discussion! Time to get on the
trainer.

Ken
"jtaylor" <[email hidden]> wrote in message
news:[email hidden]!nnrp1.uunet.ca...

Quoted message said:

"Road Man" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

My thickest 27.2 fits well with a .001 brass sheet wrapped around
it.
I guess I'll have an LBS check the ID with a guage before pulling
the
trigger on a 27.4 post. Knurling sounds like a good thing to try
on
the Laprade.

I assume you mean a .1 brass sheet, otherwise you are maiking a 27.2
into a
27.202.

Anneal the edge of the sheet, cut some 3mm slits in the edge, and
bend them
over. Voila, a seatpost shim. Go ride the bike.

Road Man said:

The brass sheet is .001 inches wrapped in a complete circle, so adding
.002 inches to the seatpost OD. The Campy post that's in place
measures
1.069 inches (equals 27.15 mm), for a total or 1.071 inches built-up
diameter,
not accounting for grease. Multiply by 25.4 mm per inch, and the
built-up
diameter is 27.20 mm.

In case it helps, aluminum soft drink cans in the US seem to be pretty
close to 0.1mm thick, so a full-circumference shim made from it should
turn a 27.2 seat post into a 27.4 seat post.

Mark

Finally, thanks to all for helping me. I think I've got this issue
sorted out now, especially with the idea that a beer can is .1 mm, on
top of course of all the other great help! Now all I have to do is
find canned beer in Ann Arbor - gotta think about that!

Ken

"Mark Janeba" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Road Man said:

The brass sheet is .001 inches wrapped in a complete circle, so
adding
.002 inches to the seatpost OD. The Campy post that's in place
measures
1.069 inches (equals 27.15 mm), for a total or 1.071 inches
built-up diameter,
not accounting for grease. Multiply by 25.4 mm per inch, and the
built-up
diameter is 27.20 mm.

In case it helps, aluminum soft drink cans in the US seem to be
pretty close to 0.1mm thick, so a full-circumference shim made from
it should turn a 27.2 seat post into a 27.4 seat post.

Mark

Ok, so here's the real end of the story.

I bought a Thomson post that was supposed to be 27.2, and it turns out
to be 27.4. It actually measures 27.33 mm (1.076 inches) in every
direction and several places along its length, so I am very impressed
with the quality control.

However, it's definitely too big for my Trek, silver-brazing
notwithstanding.

So, I should probably stick with my shimmed arrangement. I think I
want to shim with something stronger than brass sheet, because after
several R&Rs the sheet is torn in two, even with greasing.

It is possible that a 27.2 Thomson will be the fattest fit I can get
without going up a size. I might not want to ream or hone the seat
tube, at least not without a good frame man to do it.

Thanks, again!

Additional comments are welcome.

Ken

"Road Man" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

For my Trek 610, I want to try a larger seat post. The original SR
Laprade is 27.2, but it feels loose, and the integral seatpost tabs
converge when I tighted the binder bolt. I tried an old 2-bolt
Campy 27.2, and it is a bit larger, but still loose. Adding .001
brass shim stock helps. I'd like to try a 27.4 mm post, but I can't
find any on websites or the big sellers. Anyone have one to sell?

I really like the old Campy 2-bolt, cosmetics are not important!

Ken Freeman

In article <[email hidden]>,
[email hidden] says...

Quoted message said:

Finally, thanks to all for helping me. I think I've got this issue
sorted out now, especially with the idea that a beer can is .1 mm, on
top of course of all the other great help! Now all I have to do is
find canned beer in Ann Arbor - gotta think about that!

You have a one track, beer, mind. 🙂 Think coca cola. lots of those cans are
available.
-------------
Alex

In Ann Arbor I'd have to get a canned beverage at a health food store,
and they don't sell Coca-Cola. The ones they do have taste "healthy!"
Life is hard in the Peoples' Republic!

"Alex Rodriguez" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

In article <[email hidden]>,
[email hidden] says...

Quoted message said:

Finally, thanks to all for helping me. I think I've got this issue
sorted out now, especially with the idea that a beer can is .1 mm,
on
top of course of all the other great help! Now all I have to do is
find canned beer in Ann Arbor - gotta think about that!

You have a one track, beer, mind. 🙂 Think coca cola. lots of
those cans are
available.
-------------
Alex