Seatpost

Ian Blake said:

On the way from work to today I was surprised when I thought both
saddle rails had failed simultaneously, Saddle rail failure is the
usual way that my bum support gives way. But that unlikely double
failure was not the reason I was suddenly sitting on a spike. After
nine years of faithful service my Campy Chorus seatpost had snapped
at the seat clamp.

Now a long time ago when I last bought a seatpost these things were
mostly made out of aluminium alloys. Now I notice they are often
made of carbon fibre composites, including the current Chorus model.

Are there any issues with using carbon fibre seatposts in an old
steel(853) frame?

No more so than any other frame - as long as it has no rough edges to
scratch the post too badly. Perhaps get the file & sandpaper out.

Quoted message said:

I am currently thinking of getting another Chorus or should I be
thinking of something else?

Also consider one with a two-bolt clamp - for safer clamping and finer
adjustment. I like the ITM Millenium - choice of carbon and alloy versions.

~PB

Ian Blake said:

On the way from work to today I was surprised when I thought both
saddle rails had failed simultaneously, Saddle rail failure is the
usual way that my bum support gives way. But that unlikely double
failure was not the reason I was suddenly sitting on a spike. After
nine years of faithful service my Campy Chorus seatpost had snapped
at the seat clamp.

Now a long time ago when I last bought a seatpost these things were
mostly made out of aluminium alloys. Now I notice they are often
made of carbon fibre composites, including the current Chorus model.

Are there any issues with using carbon fibre seatposts in an old
steel(853) frame?

I am currently thinking of getting another Chorus or should I be
thinking of something else?

Two issues around carbon, which are closely related. They don't like being
scratched when slid into the frame (potential crack line), and the clamping
needs to avoid "pinching" the carbon fibre (crushes the resin, leading to
failure). Most better posts have specific clamps to avoid the pinch issue,
but that doesn't work on a traditional frame with the clamp integral with
the seat tube.

I have a Roberts audax bike (posh steel frame), and I asked them about
swapping to a carbon post. They said not to use one, and to either stay with
alloy or use titanium. There aren't many titanium posts easily found in the
UK, think the main two are Van Nicholas (aka Airborne available from
BikePlus) and USE (lots of sources). Van Nicholas are cheaper.

I think Campagnolo still do an alloy post lower down the range.

There are cheap "carbon" posts which are in fact alloy with a wrap of carbon
fibre to finish the surface. Can't see the point of those myself, except for
the dedicated follower of fashion.

- Nigel

--
Nigel Cliffe,
Webmaster at http://www.2mm.org.uk/

Ian Blake said:

Are there any issues with using carbon fibre seatposts in an old
steel(853) frame?

I dunno how relevant this is in your application but there can be
problems of galvanic corrosion caused at metal to carbon fibre
interfaces. I've seen it in aluminium/carbon structures (an antenna,
not a bike) but I don't know about steel/carbon.

Chris
--
Chris Eilbeck

in message <[email hidden]>, Pete Biggs

(') said:

Ian Blake said:

On the way from work to today I was surprised when I thought both
saddle rails had failed simultaneously, Saddle rail failure is the
usual way that my bum support gives way. But that unlikely double
failure was not the reason I was suddenly sitting on a spike. After
nine years of faithful service my Campy Chorus seatpost had snapped
at the seat clamp.

Now a long time ago when I last bought a seatpost these things were
mostly made out of aluminium alloys. Now I notice they are often
made of carbon fibre composites, including the current Chorus model.

Are there any issues with using carbon fibre seatposts in an old
steel(853) frame?

No more so than any other frame - as long as it has no rough edges to
scratch the post too badly. Perhaps get the file & sandpaper out.

Quoted message said:

I am currently thinking of getting another Chorus or should I be
thinking of something else?

Also consider one with a two-bolt clamp - for safer clamping and finer
adjustment. I like the ITM Millenium - choice of carbon and alloy
versions.

In my experience the USE Alien - I have the aluminium one since the
titanium and carbon versions are only a smidge lighter - offers fine
adjustment and good clamping at less weight than most two-bolt clamps, and
is easier to adjust.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

Morning had broken, and I found when I looked that we had run out
of copper roove nails.

Ian Blake said:

On the way from work to today I was surprised when I thought both saddle rails
had failed simultaneously, Saddle rail failure is the usual way that my bum
support gives way. But that unlikely double failure was not the reason I was
suddenly sitting on a spike. After nine years of faithful service my Campy
Chorus seatpost had snapped at the seat clamp.

[snip]

I don't know how unlikely double rail failure is, but it's happened to
me recently with a Brooks Professional. It was a few years old but even
so ...

--
Anthony Campbell - [email hidden]
Microsoft-free zone - Using Linux Gnu-Debian
http://www.acampbell.org.uk (blog, book reviews,
on-line books and sceptical articles)

in message <[email hidden]>, Anthony Campbell

(') said:

Ian Blake said:

On the way from work to today I was surprised when I thought both saddle
rails
had failed simultaneously, Saddle rail failure is the usual way that my
bum
support gives way. But that unlikely double failure was not the reason
I was
suddenly sitting on a spike. After nine years of faithful service my
Campy Chorus seatpost had snapped at the seat clamp.

I don't know how unlikely double rail failure is, but it's happened to
me recently with a Brooks Professional. It was a few years old but even
so ...

You scare me, guys. I've never broken even one rail!

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

;; my other religion is Emacs

Ian Blake said:

I am currently thinking of getting another Chorus or should I be thinking of
something else?

Thank you. You have been very helpful ruling out carbon for me. I have the old
style integrated seat tube clamp.

My problem has suddenly got a lot worse. When I pulled the broken post out I
saw something quite horrible, I looked at the size stamp and saw the terrible
figure of 27 without the all important point two. As we all know 27.2 is
standard, 27.0 is exotic.

I went over to the LBS but they only had one 27.0 (most shops only have 27.2).
Selcof make some nice posts but this is not one of them. I bought it anyway it
keeps the bike running. At £7 I can afford to throw it in the spares box when I
find something less chunky.

Ian Blake said:

My problem has suddenly got a lot worse. When I pulled the broken
post out I saw something quite horrible, I looked at the size stamp
and saw the terrible figure of 27 without the all important point
two. As we all know 27.2 is standard, 27.0 is exotic.

I went over to the LBS but they only had one 27.0 (most shops only
have 27.2). Selcof make some nice posts but this is not one of them.
I bought it anyway it keeps the bike running. At £7 I can afford to
throw it in the spares box when I find something less chunky.

ITM and USE have/do made/make some nice posts in 25.0, and USE make a 25.0
to 27.0 shim.

~PB

in message <[email hidden]>, Ian Blake

(') said:

On Fri, 08 Jun 2007 21:51:32 +0100, Ian Blake <[email hidden]>

Quoted message said:

I am currently thinking of getting another Chorus or should I be thinking
of something else?

Thank you. You have been very helpful ruling out carbon for me. I have
the old style integrated seat tube clamp.

My problem has suddenly got a lot worse. When I pulled the broken post
out I
saw something quite horrible, I looked at the size stamp and saw the
terrible
figure of 27 without the all important point two. As we all know 27.2 is
standard, 27.0 is exotic.

Shim. You need 0.1mm shim stock, AKA Coke can.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

There are no messages. The above is just a random stream of
bytes. Any opinion or meaning you find in it is your own creation.

Simon Brooke said:

in message <[email hidden]>, Ian Blake

(') said:

On Fri, 08 Jun 2007 21:51:32 +0100, Ian Blake <[email hidden]>

Quoted message said:

I am currently thinking of getting another Chorus or should I be
thinking of something else?

Thank you. You have been very helpful ruling out carbon for me. I
have the old style integrated seat tube clamp.

My problem has suddenly got a lot worse. When I pulled the broken
post out I
saw something quite horrible, I looked at the size stamp and saw the
terrible
figure of 27 without the all important point two. As we all know
27.2 is standard, 27.0 is exotic.

Shim. You need 0.1mm shim stock, AKA Coke can.

Can you get negative shim :-)

--
Nigel Cliffe,
Webmaster at http://www.2mm.org.uk/

Nigel Cliffe said:

Simon Brooke said:

Shim. You need 0.1mm shim stock, AKA Coke can.

Can you get negative shim :-)

It would be tremendously useful. Plenty of occasions I could really
have done with a -0.1mm shim.

regards, Ian SMith
--
|\ /| no .sig
|o o|
|/ \|

Ian Blake said:

On Fri, 08 Jun 2007 21:51:32 +0100, Ian Blake <[email hidden]>

Quoted message said:

I am currently thinking of getting another Chorus or should I be
thinking of something else?

Thank you. You have been very helpful ruling out carbon for me. I
have the old style integrated seat tube clamp.

My problem has suddenly got a lot worse. When I pulled the broken
post out I saw something quite horrible, I looked at the size stamp
and saw the terrible figure of 27 without the all important point
two. As we all know 27.2 is standard, 27.0 is exotic.

I went over to the LBS but they only had one 27.0 (most shops only
have 27.2). Selcof make some nice posts but this is not one of them.
I bought it anyway it keeps the bike running. At £7 I can afford to
throw it in the spares box when I find something less chunky.

USE used to do the aluminium alien in 27.0 (I have one), may be worth an
email to see if they still have stock.

Alternatively, a smaller diameter of choice plus a shim to take it to 27.0.
If in trouble for shims, then a plastic 27.2mm shim will take a few minutes
to gently sand down to 27.0 (place shim around seatpost, sand gently with
abrasive wrapped around the shim).

If stuck for thin shim material to increase diameter, then beer/coke can is
ideal; it cuts with scissors.

I have a spare somewhat chunky 27.0mm post if you are stuck. However, I
suspect its not significantly better than the cheap Selcof example

- Nigel

--
Nigel Cliffe,
Webmaster at http://www.2mm.org.uk/

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

Quoted message said:

Simon Brooke said:

in message <[email hidden]>, Ian Blake

(') said:

On Fri, 08 Jun 2007 21:51:32 +0100, Ian Blake <[email hidden]>
wrote:

Quoted message said:

Quoted message said:

Quoted message said:

figure of 27 without the all important point two. As we all know
27.2 is standard, 27.0 is exotic.

Shim. You need 0.1mm shim stock, AKA Coke can.

Can you get negative shim :-)

26.8mm seatpins are much more common than 27.0mm

Nigel Cliffe wrote on 09/06/2007 18:56 +0100:

Quoted message said:

Can you get negative shim :-)

Yes look under the file for negative shims ;-)

--
Tony

"The most savage controversies are those about matters as to which there
is no good evidence either way."
- Bertrand Russell

On Fri, 08 Jun 2007 21:51:32 +0100, Ian Blake <[email hidden]> wrote:

Thank you all, for your advice.

I bought a USE 17.0mm post. Although the website said they were unavailable
Amba Marketing had them in stock so I my LBS was able to supply it.

I am not perfectly happy. The 'cyclops' saddle interface although a light
weight solution cut into the plastic sheaf that prevents corrosion of the seat
rails of the saddle as I adjusted the angle and tightened the bolt.

On the otherhand it seams lighter than the old Chorus post it replaced despite
a slighter longer length.

We sill see if it kills my saddle or not soon and I can decide if I am happy or
not.