When to change the seatpost ?

Rocket J Squirrel wrote:
On 9/29/2008 1:45 PM wrote:

On Sep 25, 7:50 pm, Jay Beattie wrote:
On Sep 25, 6:30 pm, Tom Sherman
wrote:





Mike "Rocket J Squirrel" Elliot wrote:
On 9/25/2008 5:04 PM landotter wrote:
On Sep 26, 6:19 am, wrote:
When to change the seatpost ?
How many kilometer, years and terrible roads
is time to change my aluminum road seatpost
that came with my Giant Ocr1 2002
When it fails or develops cracks. You may also find that the branding
of the post leaves you depressed and upgrading to a name brand
that is
prominently silkscreened on the side my give you a psychological
advantage. Your personal mass is also a variable.
This is all too vague. Couldn't the OP get the post sent out for
fatigue
analysis?
As a minimum, the rider should do a daily dye penetrant inspection on
the seat post, with weekly radiographic inspection.
I got a great Chinese x-ray machine from Harbor Freight that I use
just for that. And with all the radiation spillage, I don't have to
shave my legs anymore -- or face, or cut my hair.

BTW, hasn't anyone ever broken a seatpost -- maybe a CF seatpost? I
broke the bolts on a 70's Weyless and a POS Avocet seatpost, but I
have never bent or broken an actual post.-- Jay Beattie.- Hide quoted
text -

- Show quoted text -

I've never broken a post myself, however I was riding with a friend
whose seat-rails broke.
Initially one broke, followed shortly by the second one. Fortunately
he was already being very careful after the first. He picked the seat
up and stuffed it into his jersey pocket and had to ride quite aways
standing that night...
The person in question is a Randoneur, and weighs in at about
130-135lb or so, a pretty small guy.
I replace my posts maybe every 6-8 years, at least the alluminum
ones. My old Campy Ti posts I consider a permanent install, at least
for now...

-pete

Y'know, just when I think I'm so smart that I can spot a nonsensical
question--take this topic, for example--I discover that I am far more
clueless than I wish I was.

"When to replace seatposts? Ha ha," I think, "this man knows nothing. It
is safe to make the humor of him."

Then I watch with horror as the thread expands with examples of failed
seatposts (or atleast seat-related parts, like the above case). My
initial sense of superiority fades quickly leaving behind a dark, clammy
sense of shame for cluelessness and for wanting to make the humor on
someone who, it may turn out, knows more than I about several things.


http://technology.open.ac.uk/materials/mem/mem_ccf7.htm

http://technology.open.ac.uk/materials/mem/mem_ccf6.htm

http://technology.open.ac.uk/materia.../mem_ccf14.htm

metal fatigue is a serious business. if you don't /know/ something
doesn't fatigue, _assume it does_ and behave accordingly.

On Sep 26, 6:15*pm, Don Mackie wrote:
I'm around 100kg and have broken two aluminium seat posts, one generic
and one name brand - both when undertaking ill-advised jumping-type
activities which ended in the inevitable heavy landing.
Interestingly - they both gave way at the top, clearly cracks starting
at the edge of the bolt holes. I am not an engineer but guess that
weakness is unaffected by the extension.

The heavy landing is usually avoidable, to some extent, with body
language. Try using your arms and legs as shock absorbers. I was
always taught, from the LBS owner when I was a kid right up to my team
manager racing BMX, to NEVER be on the saddle when the bike impacts
the ground. Even dropping off a curb, the only contact points should
be hands and feet. I do a real lot of jumping and some drops, and
never break seatposts doing this stuff (with the exception of one
wreck that sent my lightweight BMX racebike cartwheeling down the
track) simply due to the fact that they're not a point of contact when
the bike becomes one with the ground again. I'll ride on lots of
ligthweight things, I even had a carbon fork on my super-light
aluminum race BMX frame. Oddly enough, those carbon forks proved to
be one of the strongest parts on that bike, living through many a
cased jump, one instance of which actually broke bearings in the head
set. Prettymuch the only things I won't ride on that are super
lightweight are handlebars and pedals. I should probably add crank
arms to that list as I've broken a few, but I don't foresee that
happening on my road bike, which is the only bike I have with
ligthweight cranks.

On 9/29/2008 8:03 PM jim beam wrote:

Rocket J Squirrel wrote:
On 9/29/2008 1:45 PM wrote:

On Sep 25, 7:50 pm, Jay Beattie wrote:
On Sep 25, 6:30 pm, Tom Sherman
wrote:





Mike "Rocket J Squirrel" Elliot wrote:
On 9/25/2008 5:04 PM landotter wrote:
On Sep 26, 6:19 am, wrote:
When to change the seatpost ?
How many kilometer, years and terrible roads
is time to change my aluminum road seatpost
that came with my Giant Ocr1 2002
When it fails or develops cracks. You may also find that the
branding
of the post leaves you depressed and upgrading to a name brand
that is
prominently silkscreened on the side my give you a psychological
advantage. Your personal mass is also a variable.
This is all too vague. Couldn't the OP get the post sent out for
fatigue
analysis?
As a minimum, the rider should do a daily dye penetrant inspection on
the seat post, with weekly radiographic inspection.
I got a great Chinese x-ray machine from Harbor Freight that I use
just for that. And with all the radiation spillage, I don't have to
shave my legs anymore -- or face, or cut my hair.

BTW, hasn't anyone ever broken a seatpost -- maybe a CF seatpost? I
broke the bolts on a 70's Weyless and a POS Avocet seatpost, but I
have never bent or broken an actual post.-- Jay Beattie.- Hide
quoted text -

- Show quoted text -

I've never broken a post myself, however I was riding with a friend
whose seat-rails broke.
Initially one broke, followed shortly by the second one. Fortunately
he was already being very careful after the first. He picked the seat
up and stuffed it into his jersey pocket and had to ride quite aways
standing that night...
The person in question is a Randoneur, and weighs in at about
130-135lb or so, a pretty small guy.
I replace my posts maybe every 6-8 years, at least the alluminum
ones. My old Campy Ti posts I consider a permanent install, at least
for now...

-pete

Y'know, just when I think I'm so smart that I can spot a nonsensical
question--take this topic, for example--I discover that I am far more
clueless than I wish I was.

"When to replace seatposts? Ha ha," I think, "this man knows nothing.
It is safe to make the humor of him."

Then I watch with horror as the thread expands with examples of failed
seatposts (or atleast seat-related parts, like the above case). My
initial sense of superiority fades quickly leaving behind a dark,
clammy sense of shame for cluelessness and for wanting to make the
humor on someone who, it may turn out, knows more than I about several
things.


http://technology.open.ac.uk/materials/mem/mem_ccf7.htm

http://technology.open.ac.uk/materials/mem/mem_ccf6.htm

http://technology.open.ac.uk/materia.../mem_ccf14.htm

metal fatigue is a serious business. if you don't /know/ something
doesn't fatigue, _assume it does_ and behave accordingly.


Yikes. Okay, you have made the point. Even though I've never broken or
bent or apparently even mildly annoyed a seat post in my lifetime of
riding don't mean a darn thing.

--
Mike "Rocket J Squirrel"
Bend, Oregon