Stem Failure

David M. Grey said:

Went mountain biking today on a bike that I have not used in about

two

Quoted message said:

months. About 20 minutes into the ride I notice what looks like a

piece

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of thread coming out from the bolt that holds the faceplate clamp.

Turns

Quoted message said:

out not to be a thread but a crack. I removed the face plate and

notice

Quoted message said:

another thread sized crack running horizontally across the front.

Some

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portions of the crack went all the way through into the interior of

the

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face plate. I cut the ride short.

My question is about the mode of failure and if this is something

that

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is relatively common. I have had this stem for about 3 years and

use

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this bike for cross country mountain bike rides. No jumps or

anything

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real aggressive. The stem is a Thomson Elite. I am not knocking the

Quoted message said:

stem or Thomson's quality, but only want to provide as much info as
possible to get meaningful feedback. Thanks.

/Dave

To figure this out, it'd also probably be handy to know what kind of
tolerance the handlebar's clamp section was made to (how close to 25.4
it is - and it'd be good to know for the stem too, but it's hard to
measure a faceplated stem for that accurately). Also, I'd be curious to
know if whoever installed it was careful to have the upper and lower
bolts tightened equally/sequentially so that the upper and lower gaps
between the faceplate and stem were equal, and what torque specs were
used.

Thompson is a great company that actually responds to e-mails. I have e-mailed them in the past about their warranty policy, they said they would replace anything that fails under normal conditions — E-mail them , I bet they replace it!

-Nate

David M. Grey said:

Went mountain biking today on a bike that I have not used in about two
months. About 20 minutes into the ride I notice what looks like a
piece of thread coming out from the bolt that holds the faceplate
clamp. Turns out not to be a thread but a crack. I removed the face
plate and notice another thread sized crack running horizontally
across the front. Some portions of the crack went all the way
through into the interior of the face plate. I cut the ride short.

My question is about the mode of failure and if this is something that
is relatively common. I have had this stem for about 3 years and use
this bike for cross country mountain bike rides. No jumps or anything
real aggressive. The stem is a Thomson Elite. I am not knocking the
stem or Thomson's quality, but only want to provide as much info as
possible to get meaningful feedback. Thanks.

I had a Thomson Elite stem fail exactly this way...twice. First time was
the original mtb faceplate; wrote them and they sent a new one (I sent them
the broken one to evaluate).

Turns out the replacement faceplate was for a ROAD stem (I didn't know to
check), so I must have over-torqued the bolts to get it tight enough to hold
the bar. (This is on an old hardtail that I harly ever ride any more; I'm a
full squishy rider nowadays.) Went to prepare the bike for a ride recently,
and the faceplate broke when I pushed down to check the fork! Same exact
break -- horizontally right across the Thomson logo.

They sent me a mtb stem faceplate, but I haven't ridden the bike yet. I'm
just glad that BOTH plates broke in my garage and not out on the trails;
seems to me they have an issue to address.

Bill "teeth intact" S.

David M. Grey said:

Went mountain biking today on a bike that I have not used in about two
months. About 20 minutes into the ride I notice what looks like a piece
of thread coming out from the bolt that holds the faceplate clamp. Turns
out not to be a thread but a crack. I removed the face plate and notice
another thread sized crack running horizontally across the front. Some
portions of the crack went all the way through into the interior of the
face plate. I cut the ride short.

My question is about the mode of failure and if this is something that
is relatively common. I have had this stem for about 3 years and use
this bike for cross country mountain bike rides. No jumps or anything
real aggressive. The stem is a Thomson Elite. I am not knocking the
stem or Thomson's quality, but only want to provide as much info as
possible to get meaningful feedback. Thanks.

I agree with Jobst on this one. Buy stems that have two bolts to clamp
to the steerer tube, and four bolts to clamp the bars. It's good insurance.

Zog The Undeniable said:

David M. Grey said:

Went mountain biking today on a bike that I have not used in about
two months. About 20 minutes into the ride I notice what looks like
a piece of thread coming out from the bolt that holds the faceplate
clamp. Turns out not to be a thread but a crack. I removed the face
plate and notice another thread sized crack running horizontally
across the front. Some portions of the crack went all the way
through into the interior of the face plate. I cut the ride short.

My question is about the mode of failure and if this is something
that is relatively common. I have had this stem for about 3 years
and use this bike for cross country mountain bike rides. No jumps
or anything real aggressive. The stem is a Thomson Elite. I am not
knocking the stem or Thomson's quality, but only want to provide as
much info as possible to get meaningful feedback. Thanks.

I agree with Jobst on this one. Buy stems that have two bolts to
clamp
to the steerer tube, and four bolts to clamp the bars. It's good
insurance.

Thomson stems DO have four-bolt faceplates. If they crack open
(horizontally) in the middle, however, the bolts do no good.

Zog The partially-Undeniable said:

I agree with Jobst on this one. Buy stems that have two bolts to

clamp

Quoted message said:

to the steerer tube, and four bolts to clamp the bars. It's good

insurance.

There was a thread a while ago about two vs.four-bolt faceplates. This
question isn't quite as simple as you seem to believe.

App

Same exact

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break -- horizontally right across the Thomson logo.

how appropriate to have the break through the middle of the Thomson
logo.

David M. Grey said:

Went mountain biking today on a bike that I have not used in about two
months. About 20 minutes into the ride I notice what looks like a piece
of thread coming out from the bolt that holds the faceplate clamp. Turns
out not to be a thread but a crack. I removed the face plate and notice
another thread sized crack running horizontally across the front. Some
portions of the crack went all the way through into the interior of the
face plate. I cut the ride short.

My question is about the mode of failure and if this is something that
is relatively common. I have had this stem for about 3 years and use
this bike for cross country mountain bike rides. No jumps or anything
real aggressive. The stem is a Thomson Elite. I am not knocking the
stem or Thomson's quality, but only want to provide as much info as
possible to get meaningful feedback. Thanks.

/Dave

thomson's are machined. you're better off with something that's forged,
preferably cold forged. this way, the grain & inclusions in the
material are aligned for minimum fatigue susceptibility.

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

Quoted message said:

I had a Thomson Elite stem fail exactly this way...twice. First time was
the original mtb faceplate; wrote them and they sent a new one (I sent them
the broken one to evaluate).

Turns out the replacement faceplate was for a ROAD stem (I didn't know to
check), so I must have over-torqued the bolts to get it tight enough to hold
the bar. (This is on an old hardtail that I harly ever ride any more; I'm a
full squishy rider nowadays.) Went to prepare the bike for a ride recently,
and the faceplate broke when I pushed down to check the fork! Same exact
break -- horizontally right across the Thomson logo.

They sent me a mtb stem faceplate, but I haven't ridden the bike yet. I'm
just glad that BOTH plates broke in my garage and not out on the trails;
seems to me they have an issue to address.

I would have mailed them back the stem and asked for my money back. It is
obviously a desing defect they need to address before someone gets hurt.
A stem failure can be pretty ugly.
-----------------
Alex

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

Quoted message said:

Same exact

Quoted message said:

break -- horizontally right across the Thomson logo.

how appropriate to have the break through the middle of the Thomson
logo.

That might also point the source of the problem.
------------
Alex