Stem bolt failure

Are you being careful about torque ? If you overtighten stem bolts,
they'll break off and you can stress your bars leading to failure. Step
one - buy a torque wrench. That being said, there's a lot of
lightweight [censored] out there. I'm about to change a set of Deda bars
pre-emptively after 5 seasons/23,000 miles.
I also went through a couple of stems with my last bike purchase -
slipping bars, bending (luckily, not breaking) titanium stem bolts,
retorquing after every few rides, etc. I had picked these all based on
what was new and light at the time. Finally got smart and went to LBS
for the 411.

Hands down, the unbeatable stem for reliability is Thomson. Both of
their stems (Elite and X-2) are milled from solid blocks of aluminum,
no welds. The Elite weighs 190 g and has a 4 bolt faceplate (sturdy
steel bolts). Only comes as 26.0. I can vouch for this one as I're
ridden it for 3 1/2 years and never given it a second thought (other
than to admire it). Their new one, the X-2, has a hollowed out area on
the 2 bolt faceplate and a hollowed out area on the steerer clamp -
about 155 g, I think, and available in 31.8. Here's website:

http://www.lhthomson.com/

Good luck..........Lou D'Amelio

Colin Marshall said:

Have a Cinelli Solido/Solado stem/bar combination. On Saturday the stem
bolts went on me while riding, now a pretty sight. The stem is about 2
years old and maybe 20,000km on it, no previous crashes.

It has been suggested by several people that light weight stuff should
be replaced every couple of years at least. I don't race, so the weight
issue is a non event for me. I weigh about 200lbs, and want/need
something sturdy. About 3 years ago I broke a set of Deda handlebars,
cracked right through while riding, getting pretty concerned with the
lifespan of some of these things... I ride a Litespeed Siena, about 1
year old.

Any recommendations for something sturdy, 120 stem and 44 bars.

You could just replace the bolts if the stem isn't stripped.

Lou D'Amelio said:

Hands down, the unbeatable stem for reliability is Thomson. Both of
their stems (Elite and X-2) are milled from solid blocks of aluminum,
no welds.

Based on what? Forging is superior to milling from a solid block... the
best stems are all forged these days.

Some test data on stems can be found here:
http://www.biketechreview.com/stems/summary.htm

Ron Ruff said:

Lou D'Amelio said:

Hands down, the unbeatable stem for reliability is Thomson. Both of
their stems (Elite and X-2) are milled from solid blocks of aluminum,
no welds.

Based on what? Forging is superior to milling from a solid block... the
best stems are all forged these days.

Somebody better tell Boeing that they're making all their airplanes
using inferior techniques!

Forging *can* make a stronger, more durable part than machining.
However, machining often allows the use of a stronger material, better
part geometry, or better finish and tolerances than forging, at the
same or lower cost. Any of these other factors can have a bigger
effect on strength and durability than the relatively small property
differences between forgings and wrought bars.

Chalo Colina

"Ron Ruff" <[email hidden]> wrote in message

Quoted message said:

Some test data on stems can be found here:
http://www.biketechreview.com/stems/summary.htm

I looked at the link but couldn't get past the fact that they have the
equation wrong. Cantilever beam deflection is PL^3/3EI not PL^3/16EI. I
assume the rest is also unreliable.

Colin Marshall said:

Have a Cinelli Solido/Solado stem/bar combination. On Saturday the stem
bolts went on me while riding, now a pretty sight. The stem is about 2
years old and maybe 20,000km on it, no previous crashes.

It has been suggested by several people that light weight stuff should
be replaced every couple of years at least. I don't race, so the weight
issue is a non event for me. I weigh about 200lbs, and want/need
something sturdy. About 3 years ago I broke a set of Deda handlebars,
cracked right through while riding, getting pretty concerned with the
lifespan of some of these things... I ride a Litespeed Siena, about 1
year old.

Any recommendations for something sturdy, 120 stem and 44 bars.

Thanks

yes. you should pre-emptively replace this stuff. disregard the
"racing" definition - you're riding and putting on the miles. that's
fatigue loading.

as mentioned by lou, use a torque wrench. buy quality gear. make sure
the stem clamp at the handlebar has slightly rounded edges - reduces
stress risers. forged stems are best.

Lou D'Amelio said:

Are you being careful about torque ? If you overtighten stem bolts,
they'll break off and you can stress your bars leading to failure. Step
one - buy a torque wrench. That being said, there's a lot of
lightweight [censored] out there. I'm about to change a set of Deda bars
pre-emptively after 5 seasons/23,000 miles.
I also went through a couple of stems with my last bike purchase -
slipping bars, bending (luckily, not breaking) titanium stem bolts,
retorquing after every few rides, etc. I had picked these all based on
what was new and light at the time. Finally got smart and went to LBS
for the 411.

Hands down, the unbeatable stem for reliability is Thomson. Both of
their stems (Elite and X-2) are milled from solid blocks of aluminum,
no welds.

no welds is good, but forged is much better. attention to detail like
making sure the stem clamp has no sharp edges is paramount.

Quoted message said:

The Elite weighs 190 g and has a 4 bolt faceplate (sturdy
steel bolts). Only comes as 26.0. I can vouch for this one as I're
ridden it for 3 1/2 years and never given it a second thought (other
than to admire it). Their new one, the X-2, has a hollowed out area on
the 2 bolt faceplate and a hollowed out area on the steerer clamp -
about 155 g, I think, and available in 31.8. Here's website:

http://www.lhthomson.com/

Good luck..........Lou D'Amelio

Colin Marshall said:

Have a Cinelli Solido/Solado stem/bar combination. On Saturday the stem
bolts went on me while riding, now a pretty sight. The stem is about 2
years old and maybe 20,000km on it, no previous crashes.

It has been suggested by several people that light weight stuff should
be replaced every couple of years at least. I don't race, so the weight
issue is a non event for me. I weigh about 200lbs, and want/need
something sturdy. About 3 years ago I broke a set of Deda handlebars,
cracked right through while riding, getting pretty concerned with the
lifespan of some of these things... I ride a Litespeed Siena, about 1
year old.

Don't use titanium stem bolts.
..stlob mets miunatit esu t'noD

Chalo said:

Ron Ruff said:

Lou D'Amelio said:

Hands down, the unbeatable stem for reliability is Thomson. Both of
their stems (Elite and X-2) are milled from solid blocks of
aluminum, no welds.

Based on what? Forging is superior to milling from a solid block...
the best stems are all forged these days.

Somebody better tell Boeing that they're making all their airplanes
using inferior techniques!

Forging *can* make a stronger, more durable part than machining.
However, machining often allows the use of a stronger material, better
part geometry, or better finish and tolerances than forging, at the
same or lower cost.

This can't possibly be true across all economies of scale. If you were to
mill 10,000 stems versus forge 10,000 stems, I'm sure that the forging
process would save a whole heck of a lot of material. Sure, you need molds
and all that stuff, but you can recoup initial investment after X number of
stems.

Then again, I saw an amazing video of a CNC machine (with a bajillion
automatic tools) making aircraft wing ribs and holy [censored], it taps threads
while feeding and spinning at full speed (probably 3krpm)! Not to mention
the stopping and reversing to unthread the tap before tapping more holes.
The time investment may not be all that high, but I'll bet one goes through
tools quickly on those things.

Maybe I can get that video from my teacher...

--
Phil, Squid-in-Training

Ron Ruff said:

Lou D'Amelio said:

Hands down, the unbeatable stem for reliability is Thomson. Both of
their stems (Elite and X-2) are milled from solid blocks of aluminum,
no welds.

Based on what? Forging is superior to milling from a solid block... the
best stems are all forged these days.

Some test data on stems can be found here:
http://www.biketechreview.com/stems/summary.htm

Just to clear up something about Thomson stems - they are forged into a
rough aproximation of their final shape, and then are machined to the
final shape/finish. This is similar to what RaceFace did on their
Turbine cranks. RaceFace had to print "Forged" on the sie of their CNC
looking Turbine cranks because so many people got scared of CNC cranks
snapping back in the ultralight, multicolored MTB days of the early
90's.

Phil said:

Chalo said:

Forging *can* make a stronger, more durable part than machining.
However, machining often allows the use of a stronger material, better
part geometry, or better finish and tolerances than forging, at the
same or lower cost.

This can't possibly be true across all economies of scale. If you were to
mill 10,000 stems versus forge 10,000 stems, I'm sure that the forging
process would save a whole heck of a lot of material. Sure, you need molds
and all that stuff, but you can recoup initial investment after X number of
stems.

You are absolutely correct, but then we're not discussing *all*
economies of scale. For really cheap bike parts, forged steel is hard
to beat. And if cost is no object, then you forge the
highest-performance alloy possible, then machine it to a precision size
and finish-- or you use even more exotic materials and techniques. But
when the criterion is maximum strength-to-weight, at a known acceptable
cost, in a comparatively low-volume item (e.g. a single manufacturer's
premium stem in a single size), then it's very likely that machining
will yield better results than forging.

I expect that the Thomson stem has higher strength, stiffness, and
longevity per unit weight than most if not all forged stems in the same
price range. And if that's true, then it's because machining the stem
allows the manufacturer better control over more relevant features at a
given production cost than he would have with a forging process.

Chalo Colina

Anthony A. said:

Just to clear up something about Thomson stems - they are forged into a
rough aproximation of their final shape, and then are machined to the
final shape/finish. This is similar to what RaceFace did on their
Turbine cranks.

Earlier, I tried to find the facts about this, but I was unable to
determine that Thomson stems were machined from forgings. The only
mention of forging anywhere in the L. H. Thomson website is in the
descriptions of the seatposts.

Chalo Colina

"Chalo" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Phil said:

Chalo said:

Forging *can* make a stronger, more durable part than machining.
However, machining often allows the use of a stronger material, better
part geometry, or better finish and tolerances than forging, at the
same or lower cost.

This can't possibly be true across all economies of scale. If you were
to
mill 10,000 stems versus forge 10,000 stems, I'm sure that the forging
process would save a whole heck of a lot of material. Sure, you need
molds
and all that stuff, but you can recoup initial investment after X number
of
stems.

You are absolutely correct, but then we're not discussing *all*
economies of scale. For really cheap bike parts, forged steel is hard
to beat. And if cost is no object, then you forge the
highest-performance alloy possible, then machine it to a precision size
and finish-- or you use even more exotic materials and techniques. But
when the criterion is maximum strength-to-weight, at a known acceptable
cost, in a comparatively low-volume item (e.g. a single manufacturer's
premium stem in a single size), then it's very likely that machining
will yield better results than forging.

I expect that the Thomson stem has higher strength, stiffness, and
longevity per unit weight than most if not all forged stems in the same
price range. And if that's true, then it's because machining the stem
allows the manufacturer better control over more relevant features at a
given production cost than he would have with a forging process.

The thing is, Thomsons aren't all that light. They look nice though. I see
what you mean though.

--
Phil, Squid-in-Training

On 29 Sep 2005 06:03:50 -0700, "Anthony A." <[email hidden]>

Quoted message said:

Just to clear up something about Thomson stems - they are forged into a
rough aproximation of their final shape, and then are machined to the
final shape/finish. This is similar to what RaceFace did on their
Turbine cranks. RaceFace had to print "Forged" on the sie of their CNC
looking Turbine cranks because so many people got scared of CNC cranks
snapping back in the ultralight, multicolored MTB days of the early
90's.

But.. the strongest bit in a forging is the surface. Milling that away
seems to be pointless.

Jasper

"Jasper Janssen" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

On 29 Sep 2005 06:03:50 -0700, "Anthony A." <[email hidden]>

Quoted message said:

Just to clear up something about Thomson stems - they are forged into a
rough aproximation of their final shape, and then are machined to the
final shape/finish. This is similar to what RaceFace did on their
Turbine cranks. RaceFace had to print "Forged" on the sie of their CNC
looking Turbine cranks because so many people got scared of CNC cranks
snapping back in the ultralight, multicolored MTB days of the early
90's.

But.. the strongest bit in a forging is the surface. Milling that away
seems to be pointless.

Jasper

AFAIK, forgings compress the whole member, so even the grains far from the
surface become aligned, etc. I like the idea of a shot-peened finish
though.

Sometimes manufs claim that their stuff has a shot-peened finish, which it
indeed does, but this could simply be due to the casting process, like those
little balls or ceramic bits in investment casting... I can't think of it
now. In that case, there's no residual compressive stress at the surface to
increase the fatigue life of the product.

--
Phil, Squid-in-Training

Squid-in-Training said:

Sometimes manufs claim that their stuff has a shot-peened finish, which it
indeed does, but this could simply be due to the casting process, like those
little balls or ceramic bits in investment casting... I can't think of it
now. In that case, there's no residual compressive stress at the surface to
increase the fatigue life of the product.

If you give the forging molds a shot-peened finish, the forged product
will have it as well. And they usually do have a non-smooth finish,
presumably because it helps the molds last longer or something.

Jasper

Chalo said:

Quoted message said:

Quoted message said:

Forging *can* make a stronger, more durable part than
machining. However, machining often allows the use of
a stronger material, better part geometry, or better
finish and tolerances than forging, at the same or lower
cost.

Phil said:

Quoted message said:

This can't possibly be true across all economies of scale.
If you were to mill 10,000 stems versus forge 10,000 stems,
I'm sure that the forging process would save a whole heck
of a lot of material. Sure, you need molds and all that
stuff, but you can recoup initial investment after X number
of stems.

Chalo responds:

Quoted message said:

You are absolutely correct, but then we're not discussing
*all* economies of scale. For really cheap bike parts,
forged steel is hard to beat. And if cost is no object,
then you forge the highest-performance alloy possible, then
machine it to a precision size and finish-- or you use even
more exotic materials and techniques. But when the criterion
is maximum strength-to-weight, at a known acceptable cost, in
a comparatively low-volume item (e.g. a single manufacturer's
premium stem in a single size), then it's very likely that
machining will yield better results than forging.

I expect that the Thomson stem has higher strength,
stiffness, and longevity per unit weight than most if not
all forged stems in the same price range. And if that's
true, then it's because machining the stem allows the
manufacturer better control over more relevant features at
a given production cost than he would have with a forging
process.

Interesting. How do you think this applies in the case of hubs? I
admire both Chris King hubs and Shimano hubs, but they do take
dissimilar approaches to manufacturing the hubshell- machined versus
forged, like we're discussing here.

"Dan" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

"Ron Ruff" <[email hidden]> wrote in message

Quoted message said:

Some test data on stems can be found here:
http://www.biketechreview.com/stems/summary.htm

I looked at the link but couldn't get past the fact that they have the
equation wrong. Cantilever beam deflection is PL^3/3EI not PL^3/16EI. I
assume the rest is also unreliable.

I decided to give this page a second look and read past the error at the
top. The next thing they say is the stiffness is proportional to
pi*(Ro-Ri)^4 which is wrong. It is proportional to pi*(Ro^4-Ri^4). Jeez,
somebody needs to talk to these bone heads.

I have read several post of Cinelli Stem bolt failures. I am a lawyer. I have a client who was riding to work on a paved road. Titanium bolt on his Cinelli Solido stem broke. (Two bolt system.) He lost control, crash, broke his neck, and died. I am interested talking to anyone who has first-hand experience with Cinelli Ti bolt failures. George McLaughlin, Denver, Colorado Direct Dial: 720 542-7885. Email: [email hidden]