peugeot cracked frame

davec said:

Hello, I have an older Aluminium frame Peugeot.There is a small crack
near the top of the seat tube. It happened when a taller rider raised
the seat too high. How much of a problem is this?

Large, if the crack is below the top tube. Smaller and possibly easy
to deal with if it's above the top tube. The top of the seat tube is
one of the most heavily stressed parts of the frame; no crack there
should be ignored.

Quoted message said:

Can I just lower the
seat back down and ride or are there safety issues?

If the crack is above the top tube, is there enough of the seat tube
present that you could simply shorten it to remove the damaged area,
and then relocate the seatpost clamp? Depending on the crack's
location and orientation, it might even be possible to simply
stop-drill the crack and ride on, though I doubt that this will be the
case.

If the crack is below the top tube, or if it's above the top tube but
not in a location where removing the damaged end is an option, things
are less hopeful. If the seatpost is long enough, a failure would
probably not be of the type in which the rider is suddenly and
unexpectedly dumped from the bike at speed, but the potential for both
additional damage to the frame (rendering it completely unrepairable)
and hazard to the rider is more than I would be comfortable with.
Given that you are aware that the failure was causes by misuse,
there's no warranty issue involved. Your choices essentially come
down to repair or replacement.

Quoted message said:

What about repair
if necessary?

This is something that would have to be addressed by a frame shop.
It's possible that locating a replacement frame and transferring your
components would be a more economical solution that trying to weld the
crack, particularly if the frame is bonded instead of welded. If the
frame is bonded, there are probably more repair options than if it's
welded.
--
Typoes are a feature, not a bug.
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Werehatrack said:

On 28 Feb 2006 14:40:11 -0800, "davec" <[email hidden]> wrote:

Quoted message said:

Quoted message said:

Hello, I have an older Aluminium frame Peugeot.There is a small crack
near the top of the seat tube. It happened when a taller rider raised
the seat too high. How much of a problem is this?

Quoted message said:

If the crack is above the top tube, is there enough of the seat tube
present that you could simply shorten it to remove the damaged area,
and then relocate the seatpost clamp? Depending on the crack's
location and orientation, it might even be possible to simply
stop-drill the crack and ride on, though I doubt that this will be the
case.

Sorry, but if you are talking about a crack in the top tube being a
problem then I think this statement is false. The top tube is the
least-stressed tube in a bicycle today. That's why it was always a 1"
tube on vintage bikes, whereas seat tube and downtube were 1 1/8. The
top tube is under compression. This is not a severe load. Dents in
the top tube - bad ones - often produce no structural consequences.

The downtube is the most heavily stressed tube, since your whole body
weight is trying to rip the downtube out from the bottom bracket and
from the lower head lug. The seat tube takes a lot of flexion from
pedaling and so cracks in the seat tube (especially near the bottom
bracket area) can easily grow.

If the crack is in the seat lug, if any, then I think you are in
trouble because the crack will likely grow larger. Depending on the
location you should probably either attempt to sand or file smooth the
insides of the crack to remove stress risers and prevent it from
growing larger, or just ditch the frameset. If you keep the frame it
want be good to get a well-fitting 400mm post in an attempt to spread
the torque from your body over a wider area of the seat tube.

- Don Gillies
San Diego, CA

Werehatrack said:

On 28 Feb 2006 14:40:11 -0800, "davec" <[email hidden]> wrote:

Quoted message said:

Quoted message said:

Hello, I have an older Aluminium frame Peugeot. There is a small
crack near the top of the seat tube. It happened when a taller
rider raised the seat too high. How much of a problem is this?

Quoted message said:

If the crack is above the top tube, is there enough of the seat tube
present that you could simply shorten it to remove the damaged area,
and then relocate the seatpost clamp? Depending on the crack's
location and orientation, it might even be possible to simply
stop-drill the crack and ride on, though I doubt that this will be
the
case.

Sorry, but if you are talking about a crack in the top tube being a
problem then I think this statement is false. The top tube is the
least-stressed tube in a bicycle today. That's why it was always a 1"
tube on vintage bikes, whereas seat tube and downtube were 1 1/8, and
on many high-tech bikes the downtube is 2x larger than any other tube.
The top tube is under compression. This is not a severe load. Dents
in the top tube - bad ones - often produce no structural consequences.

The downtube is the most heavily stressed tube, since your whole body
weight is trying to rip the downtube out from the bottom bracket and
from the lower head tube/lug. The seat tube takes a lot of flexion
from pedaling in the bb area and so cracks in the seat tube
(especially near the bottom bracket area) can easily grow.

If the crack is in the seat lug, above the top tube, then it may not
grow larger. Depending on the location you should probably either
attempt to sand or file smooth the insides of the crack to remove
stress risers and prevent it from growing larger, or just ditch the
frameset. If you keep the frame I would at least get a well-fitting
400mm post in an attempt to spread the torque from your body over a
wider area of the seat tube.

- Don Gillies
San Diego, CA

On 28 Feb 2006 18:46:11 -0800, [email hidden] (Donald Gillies)

Quoted message said:

Werehatrack said:

On 28 Feb 2006 14:40:11 -0800, "davec" <[email hidden]> wrote:

Quoted message said:

Quoted message said:

Hello, I have an older Aluminium frame Peugeot. There is a small
crack near the top of the seat tube. It happened when a taller
rider raised the seat too high. How much of a problem is this?

Quoted message said:

If the crack is above the top tube, is there enough of the seat tube
present that you could simply shorten it to remove the damaged area,
and then relocate the seatpost clamp? Depending on the crack's
location and orientation, it might even be possible to simply
stop-drill the crack and ride on, though I doubt that this will be
the
case.

Sorry, but if you are talking about a crack in the top tube

The OP stated that the crack is in the seat tube.

Quoted message said:

being a
problem then I think this statement is false. The top tube is the
least-stressed tube in a bicycle today.

The top tube is not under discussion.

Quoted message said:

That's why it was always a 1"
tube on vintage bikes, whereas seat tube and downtube were 1 1/8, and
on many high-tech bikes the downtube is 2x larger than any other tube.
The top tube is under compression. This is not a severe load. Dents
in the top tube - bad ones - often produce no structural consequences.

It's a crack, not a dent, and it's in the seat tube.

Quoted message said:

The downtube is the most heavily stressed tube, since your whole body
weight is trying to rip the downtube out from the bottom bracket and
from the lower head tube/lug. The seat tube takes a lot of flexion
from pedaling in the bb area and so cracks in the seat tube
(especially near the bottom bracket area) can easily grow.

Which is exactly what is under discussion.

Quoted message said:

If the crack is in the seat lug, above the top tube, then it may not
grow larger.

Stated location was in the tube. The frame is aluminum, so lugs are
unlikely; even bonded frames typically used internally-fitted sleeve
joints.

Quoted message said:

Depending on the location you should probably either
attempt to sand or file smooth the insides of the crack to remove
stress risers and prevent it from growing larger, or just ditch the
frameset. If you keep the frame I would at least get a well-fitting
400mm post in an attempt to spread the torque from your body over a
wider area of the seat tube.

A crack in aluminum in an area subject to flexing will grow if not
stop-drilled (or the equivalent). Filing the edges will do nothing
unless the propagating end of the crack is opened to a smooth margin;
that's what a stop-drill accomplishes. If the crack is below the top
tube, I question the wisdom of trying to sleeve it with a long post.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

davec said:

Hello, I have an older Alummium frame Peugeot.There is a small crack
near the top of the seat tube.It happened when a taller rider raised
the seat to high.How much of a problem is this? Can I just lower the
seat back down and ride or are there safety issues? What about repair
if necessary?

thanks dave

cracking is a serious issue - it can lead to sudden catastrophic
failure, and personal injury.

if you can post a pic here, it would be handy. if not, discontinue use
as the prudent action. repair of aluminum frames is uneconomic as they
require heat treatment.

davec said:

Hello, I have an older Alummium frame Peugeot.There is a small crack
near the top of the seat tube.It happened when a taller rider raised
the seat to high.How much of a problem is this? Can I just lower the
seat back down and ride or are there safety issues? What about repair
if necessary?

If the crack is above the top tube, there's probably no danger from
catastrophic failure. If the crack is small enough, drill 2 small holes,
one at each end of the crack. That's about the only practical repair. It
might help to use the longest seatpost you can find.

davec said:

Hello, I have an older Alummium frame Peugeot.There is a small crack
near the top of the seat tube.It happened when a taller rider raised
the seat to high.How much of a problem is this? Can I just lower the
seat back down and ride or are there safety issues? What about repair
if necessary?

thanks dave

Is the crack vertical or horizontal?
EJ in NJ