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.
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
Quoted message said:
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
Quoted message said:
portions of the crack went all the way through into the interior of
the
Quoted message said:
face plate. I cut the ride short.
My question is about the mode of failure and if this is something
that
Quoted message said:
is relatively common. I have had this stem for about 3 years and
use
Quoted message said:
this bike for cross country mountain bike rides. No jumps or
anything
Quoted message said:
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!
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.
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.
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.
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.
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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
