2 bolt vs 4 bolt stems

On Tue, 20 Dec 2005 13:34:49 -0800, "G.T." <[email hidden]>

Quoted message said:

I'm shopping for a road stem to use on a 'cross bike and haven't found a
definitive answer regarding the benefits/liabilities of the two styles with
regards to stem and bar longevity.

From searching I see the tide leaning towards 2 bolt for the steerer clamp,
4 bolt for the face plate, and forged rather than machined. I assume forged
and a 2 bolt steerer clamp is definitely the way to go but how about the
number of bolts holding the faceplate on?

Due to a number of issues, many feel that a two-bolt clamp on the bar
is inadequate. My own opinion leans strongly toward agreement with
that contention. From what I have seen, using four bolts on the bar
clamp not only provides redundancy but also greatly reduces the
tendency for uneven bar loading to cause the clamp to flex open and
place undue strain on the fastener threads. The steerer clamp is
generally a more robust design that doesn't use a separate cap; as
such, two bolts is plenty for that location.
--
Typoes are a feature, not a bug.
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Greg T? said:

I'm shopping for a road stem to use on a 'cross bike and haven't
found a definitive answer regarding the benefits/liabilities of the
two styles with regards to stem and bar longevity.

Quoted message said:

From searching I see the tide leaning toward 2 bolt for the steerer
clamp, 4 bolt for the face plate, and forged rather than machined.
I assume forged and a 2 bolt steerer clamp is definitely the way to
go but how about the number of bolts holding the faceplate on?

For those of us who have had various stem bolt failures on quill
stems, there is a definite preference for redundancy in a system in
which clamp failure means the bars fall off as with a threadless
steertube. With a quill (Cinelli) stem at least the hardware didn't
fall off but got loose. For that reason, for me two clamp bolts on the
steerer and two pairs of clamp bolts for the bars is a must.

Jobst Brandt

G.T. said:

I'm shopping for a road stem to use on a 'cross bike and haven't
found a definitive answer regarding the benefits/liabilities of the
two styles with regards to stem and bar longevity.

From searching I see the tide leaning towards 2 bolt for the steerer
clamp, 4 bolt for the face plate, and forged rather than machined. I
assume forged and a 2 bolt steerer clamp is definitely the way to go
but how about the number of bolts holding the faceplate on?

Thanks,
Greg

Don't even think about less than four for the faceplate. You'll wonder why
the bike is noodly and may not pinpoint the stem as being the culprit. The
30-gram weight savings is piddling compared to the difference in stiffness.

On that note, I've never heard of a stem bolt failure but I know others on
the NG have, personally, too. I've only seen fractures around the bolt
eyelets, mostly due to uneven loading.
--
Phil, Squid-in-Training

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

Quoted message said:

On Tue, 20 Dec 2005 13:34:49 -0800, "G.T." <[email hidden]>

Quoted message said:

I'm shopping for a road stem to use on a 'cross bike and haven't found a
definitive answer regarding the benefits/liabilities of the two styles

with

Quoted message said:

Quoted message said:

regards to stem and bar longevity.

From searching I see the tide leaning towards 2 bolt for the steerer

clamp,

Quoted message said:

Quoted message said:

4 bolt for the face plate, and forged rather than machined. I assume

forged

Quoted message said:

Quoted message said:

and a 2 bolt steerer clamp is definitely the way to go but how about the
number of bolts holding the faceplate on?

Due to a number of issues, many feel that a two-bolt clamp on the bar
is inadequate. My own opinion leans strongly toward agreement with
that contention. From what I have seen, using four bolts on the bar
clamp not only provides redundancy but also greatly reduces the
tendency for uneven bar loading to cause the clamp to flex open and
place undue strain on the fastener threads. The steerer clamp is
generally a more robust design that doesn't use a separate cap; as
such, two bolts is plenty for that location.

I read an article (TOUR magazin?) where they adviced that on lightweight
aluminium bars and carbon bars to use a 4 bolt clamp only if that clamp
consists of two seperate clamps like the new Ritchey WCS because of the
danger of uneven load on the bar with a one piece clamp and 4 bolts.

Lou

Lou Holtman said:

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

Quoted message said:

Due to a number of issues, many feel that a two-bolt clamp on the bar
is inadequate. My own opinion leans strongly toward agreement with
that contention. From what I have seen, using four bolts on the bar
clamp not only provides redundancy but also greatly reduces the
tendency for uneven bar loading to cause the clamp to flex open and
place undue strain on the fastener threads. The steerer clamp is
generally a more robust design that doesn't use a separate cap; as
such, two bolts is plenty for that location.

I read an article (TOUR magazin?) where they adviced that on lightweight
aluminium bars and carbon bars to use a 4 bolt clamp only if that clamp
consists of two seperate clamps like the new Ritchey WCS because of the
danger of uneven load on the bar with a one piece clamp and 4 bolts.

IMO, a bar so dainty that it would be endangered by the use of a
single four-bolt clamp (or any other properly-designed clamp) is not a
bar that I'd want to use anyway...and a properly designed single cap
using four bolts will have a good chance of spreading the compression
over a larger area of the bar than two smaller clamps. I think the
writer was reaching for a justification to recommend the New Thing, as
is often the case when a specialist mag covers a design change.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

Phil Lee said:

Quoted message said:

I'm shopping for a road stem to use on a 'cross bike and haven't
found a definitive answer regarding the benefits/liabilities of the
two styles with regards to stem and bar longevity.

Quoted message said:

Quoted message said:

From searching I see the tide leaning towards 2 bolt for the
steerer clamp, 4 bolt for the face plate, and forged rather than
machined. I assume forged and a 2 bolt steerer clamp is definitely
the way to go but how about the number of bolts holding the
faceplate on?

Quoted message said:

Don't even think about less than four for the faceplate. You'll
wonder why the bike is noodly and may not pinpoint the stem as being
the culprit. The 30-gram weight savings is piddling compared to the
difference in stiffness.

The quill stem gets most of its flexing from not being clamped at the
top of the steertube and fro its slender forward reach that acts as a
torsion bar. You won't find either of these 1/10 as great with any
threadless steer tube stem. The diameter of the reach is about twice
a s large and the attachment to the steer tube must be solid or the
stem would walk right off the top of the steertube, something you
would notice with a decidedly loose head bearing before separation.

The issue is fail-safe operation and that is why double clamping is
essential. It is not a matter of performance.

Quoted message said:

On that note, I've never heard of a stem bolt failure but I know
others on the NG have, personally, too. I've only seen fractures
around the bolt eyelets, mostly due to uneven loading.

I have had a stem expander fail. Stem bolts on quill stems with the
slant wedge expanders unscrew under heavy climbing forces. I had
handlebar free rotation on climbs and had to stop to tighten the
expander bolt. Bar clamps on (typically Cinelli) quill stems are only
lightly loaded and don't fail and cannot release the bar even on
failure while the ones on threadless stems will release the bars
completely if there is no redundancy.

Jobst Brandt

On Wed, 21 Dec 2005 17:46:23 GMT, Werehatrack <[email hidden]>

Quoted message said:

Lou Holtman said:

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

Quoted message said:

Due to a number of issues, many feel that a two-bolt clamp on the bar
is inadequate. My own opinion leans strongly toward agreement with
that contention. From what I have seen, using four bolts on the bar
clamp not only provides redundancy but also greatly reduces the
tendency for uneven bar loading to cause the clamp to flex open and
place undue strain on the fastener threads. The steerer clamp is
generally a more robust design that doesn't use a separate cap; as
such, two bolts is plenty for that location.

I read an article (TOUR magazin?) where they adviced that on lightweight
aluminium bars and carbon bars to use a 4 bolt clamp only if that clamp
consists of two seperate clamps like the new Ritchey WCS because of the
danger of uneven load on the bar with a one piece clamp and 4 bolts.

IMO, a bar so dainty that it would be endangered by the use of a
single four-bolt clamp (or any other properly-designed clamp) is not a
bar that I'd want to use anyway...and a properly designed single cap
using four bolts will have a good chance of spreading the compression
over a larger area of the bar than two smaller clamps. I think the
writer was reaching for a justification to recommend the New Thing, as
is often the case when a specialist mag covers a design change.

Actually my new Easton EC90 Equipe carbon bar came with instructions to not use
it with a 4 bolt clamp. Doesn't make a lot of sense to me. It seems to me the
width of the clamp would be at least as important as the number of bolts. I
will however use it with a 2 bolt stem.

Werehatrack said:

Due to a number of issues, many feel that a two-bolt clamp on the bar
is inadequate. My own opinion leans strongly toward agreement with
that contention. From what I have seen, using four bolts on the bar
clamp not only provides redundancy but also greatly reduces the
tendency for uneven bar loading to cause the clamp to flex open and
place undue strain on the fastener threads. The steerer clamp is
generally a more robust design that doesn't use a separate cap; as
such, two bolts is plenty for that location.

4 bolt clamps typically use smaller bolts than 2 bolt clamps
(5mm vs 6mm). Nominally, the 4 bolts are stronger anyway,
but not twice as much. While there is some redundancy in
a 4 bolt clamp, I would not like to rely on it very strongly.

With a four bolt clamp, it is possible to tighten the bolts to
quite different torques and still clamp the bar. If this happens,
under loading the load is not evenly distributed, and effectively
carried by fewer than four bolts. Also the looser bolts might
become unloaded and gradually work free. So be careful
to get all the bolts to similar torques. This isn't a fatal weakness,
just an example of "don't install improperly." But it is a type of
improper installation that used not to exist, so not everyone
is looking out for it.

Quoted message said:

With a four bolt clamp, it is possible to tighten the bolts to
quite different torques and still clamp the bar.

Tighten in a star (box) pattern...
--
Phil, Squid-in-Training

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

Quoted message said:

Actually my new Easton EC90 Equipe carbon bar came with instructions to not

use

Quoted message said:

it with a 4 bolt clamp. Doesn't make a lot of sense to me. It seems to me

the

Quoted message said:

width of the clamp would be at least as important as the number of bolts. I
will however use it with a 2 bolt stem.

The reason for the Easton warning is very simple. Easton only sells two bolt
stems. They want you to use their stems.
-------------
Alex

jobst.brandt said:

Greg T? said:

I'm shopping for a road stem to use on a 'cross bike and haven't found a
definitive answer regarding the benefits/liabilities of the two styles
with regards to stem and bar longevity.

Quoted message said:

From searching I see the tide leaning toward 2 bolt for the steerer
clamp, 4 bolt for the face plate, and forged rather than machined. I
assume forged and a 2 bolt steerer clamp is definitely the way to go but
how about the number of bolts holding the faceplate on?

For those of us who have had various stem bolt failures on quill stems,
there is a definite preference for redundancy in a system in which clamp
failure means the bars fall off as with a threadless steertube. With a
quill (Cinelli) stem at least the hardware didn't fall off but got loose.
For that reason, for me two clamp bolts on the steerer and two pairs of
clamp bolts for the bars is a must.

I agree, but stems like this are hard to find. And if you do find one,
there's no telling how good the rest of it is. That is, it may have
four bolts, but will the welds crack, or will a machined body (with tool
marks) hold up as well as a forged one?

Also, what about hinged bar clamps, with a hinge on top and two bolts on
the bottom? These seem pretty good to me too.

Matt O.

Phil said:

Don't even think about less than four for the faceplate. You'll wonder why
the bike is noodly and may not pinpoint the stem as being the culprit. The
30-gram weight savings is piddling compared to the difference in stiffness.

Seems like stiffness is going to be more proportional to the stem
extension diameter, and the properties of the handlebar, than the
number of bolts on the bar clamp.

Quoted message said:

On that note, I've never heard of a stem bolt failure but I know others on
the NG have, personally, too. I've only seen fractures around the bolt
eyelets, mostly due to uneven loading.

Just to inject some test data into the discussion:
http://www.biketechreview.com/stems/index.htm

Briefly, the welded stems tended to fail at the welds and one-piece
stems tended to fail at tool marks or wall thickness transitions in the
extension. Many of the 10 stems tested exhibited wear at the bar clamp,
but only one (a two-bolt design) failed there. One of the fixing bolts
was undersize and the stem was designed with insufficient thread
engagement, leading to stripped threads.

Based on this test, I'd be more wary of undersized hardware and shallow
thread engagement than the number of bolts on the bar clamp.

JLS

Matt O'Toole said:

Quoted message said:

Quoted message said:

I'm shopping for a road stem to use on a 'cross bike and haven't
found a definitive answer regarding the benefits/liabilities of
the two styles with regards to stem and bar longevity.

Quoted message said:

Quoted message said:

Quoted message said:

From searching I see the tide leaning toward 2 bolt for the
steerer clamp, 4 bolt for the face plate, and forged rather than
machined. I assume forged and a 2 bolt steerer clamp is definitely
the way to go but how about the number of bolts holding the
faceplate on?

Quoted message said:

Quoted message said:

For those of us who have had various stem bolt failures on quill
stems, there is a definite preference for redundancy in a system in
which clamp failure means the bars fall off as with a threadless
steertube. With a quill (Cinelli) stem at least the hardware
didn't fall off but got loose. For that reason, for me two clamp
bolts on the steerer and two pairs of clamp bolts for the bars is a
must.

Quoted message said:

I agree, but stems like this are hard to find. And if you do find
one, there's no telling how good the rest of it is. That is, it may
have four bolts, but will the welds crack, or will a machined body
(with tool marks) hold up as well as a forged one?

How about these:

http://www.ritcheylogic.com/
http://www.ritcheylogic.com/stems.htm

Quoted message said:

Also, what about hinged bar clamps, with a hinge on top and two
bolts on the bottom? These seem pretty good to me too.

That is if they have two screws clamping the steertube.

Jobst Brandt

Quoted message said:

How about these:

http://www.ritcheylogic.com/
http://www.ritcheylogic.com/stems.htm

Quoted message said:

Also, what about hinged bar clamps, with a hinge on top and two
bolts on the bottom? These seem pretty good to me too.

That is if they have two screws clamping the steertube.

Jobst Brandt

I use a Ritchey WCS with a set of Easton CF drop bars. After seeing
that stem testing article, I was reassured that I made a good choice.

I use a 100mm in length and I sure didn't notice any stiffness
differences between the 4 bolt plate and the generic 2 -bolt face
plate stem, that I had been using. I choose the WCS because of
recommendations from I believe Peter and I liked the appearance. I
also got it for less than full price.

Life is Good!
Jeff

Alex Rodriguez said:

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

Quoted message said:

Actually my new Easton EC90 Equipe carbon bar came with instructions to not

use

Quoted message said:

it with a 4 bolt clamp. Doesn't make a lot of sense to me. It seems to me

the

Quoted message said:

width of the clamp would be at least as important as the number of bolts. I
will however use it with a 2 bolt stem.

The reason for the Easton warning is very simple. Easton only sells two bolt
stems. They want you to use their stems.

Here's their "logic."

Forgive me if this was already posted in this thread....

http://nbeener.com/EASTON_TWO_BOLTS_vs_FOUR.pdf
--
Live simply so that others may simply live

Jeff Starr said:

Quoted message said:

How about these:

http://www.ritcheylogic.com/
http://www.ritcheylogic.com/stems.htm

Quoted message said:

Quoted message said:

Quoted message said:

Also, what about hinged bar clamps, with a hinge on top and two
bolts on the bottom? These seem pretty good to me too.

Quoted message said:

Quoted message said:

That is if they have two screws clamping the steertube.

Quoted message said:

I use a Ritchey WCS with a set of Easton CF drop bars. After seeing
that stem testing article, I was reassured that I made a good
choice.

Quoted message said:

I use a 100mm in length and I sure didn't notice any stiffness
differences between the 4 bolt plate and the generic 2 -bolt face
plate stem, that I had been using. I choose the WCS because of
recommendations from I believe Peter and I liked the appearance. I
also got it for less than full price.

There is no difference between number of screws that you can feel
because that would require that the clamp was loose for there to be
relative motion (something you can feel). Safety is entire
difference. Screws can fail for one reason or another, such as threads
pulling out of the aluminum or a crack in the screw itself.

Because these stems work the way they do, no single screw should alone
be be able to release the bar from the bicycle. That is why I believe
in two bolt clamping to the steer tube and four for the bar clamp.
That way there is a redundancy.

Jobst Brandt

James Scott said:

Phil said:

Don't even think about less than four for the faceplate. You'll
wonder why the bike is noodly and may not pinpoint the stem as being
the culprit. The 30-gram weight savings is piddling compared to the
difference in stiffness.

Seems like stiffness is going to be more proportional to the stem
extension diameter, and the properties of the handlebar, than the
number of bolts on the bar clamp.

It was very obvious when riding my roommate's bike that there was visible
deflection of the faceplate *at the clamp*.

When you have a narrow faceplate/clamp, and only two bolts, that means you
have no torsional rigidity. Think about it: the next time you get Chinese,
take 6 chopsticks and a friend. Take one horizontally; that is the
handlebar. Take two more chopsticks and have your friend hold them on top
of and below the handlebar chopstick, touching. This is a 2-bolt clamp.
How hard is it to rotate the chopstick (like a propeller)? Totally easy...
your friend/2 chopsticks would never have the strength to hold it in place.
Now, use the other remaining 2 chopsticks, and place them as how they would
be in a 4-bolt faceplate. How hard is it to rotate now? Much harder.

Quoted message said:

Quoted message said:

On that note, I've never heard of a stem bolt failure but I know
others on the NG have, personally, too. I've only seen fractures
around the bolt eyelets, mostly due to uneven loading.

Just to inject some test data into the discussion:
http://www.biketechreview.com/stems/index.htm

Briefly, the welded stems tended to fail at the welds and one-piece
stems tended to fail at tool marks or wall thickness transitions in
the extension. Many of the 10 stems tested exhibited wear at the bar
clamp, but only one (a two-bolt design) failed there. One of the
fixing bolts was undersize and the stem was designed with
insufficient thread engagement, leading to stripped threads.

Based on this test, I'd be more wary of undersized hardware and
shallow thread engagement than the number of bolts on the bar clamp.

My OP was about flex, not failure. Shallow thread engagement also worries
me, though. Once I was building a BMX bike and the stem had 2.5 threads
engaged. Thankfully, it stripped upon bike build-up and not use.

--
Phil, Squid-in-Training

Phil Lee said:

Quoted message said:

Quoted message said:

Don't even think about less than four for the faceplate. You'll
wonder why the bike is noodly and may not pinpoint the stem as
being the culprit. The 30-gram weight savings is piddling
compared to the difference in stiffness.

Quoted message said:

Quoted message said:

Seems like stiffness is going to be more proportional to the stem
extension diameter, and the properties of the handlebar, than the
number of bolts on the bar clamp.

Quoted message said:

It was obvious when riding my roommate's bike that there was visible
deflection of the faceplate *at the clamp*.

That's a basically bad design in which extended screws are loaded in
bending. Screws are tension elements and don't work in the bending
mode as we see on pedals that auger into the face of cranks because
they are always moving... until the crank breaks off. Two screws can
be made to work well if the clamp is designed to not load the screws
in bending. However, that does not address the fail safe aspect of
such stems.

Unfortunately components are not generally designed by engineers who
understand the concepts or work under a manager who does. The logo of
a well known brand is no guarantee of proper designed. For example
some major blunders such as Shimano Octalink or Campagnolo Delta brake
as examples, both of which went through two versions while not
recognizing why the design was basically flawed. There have been
others, such as the Cinelli fork crown or the quill stem, both of
which produced predictable failures. Another was Specialized Umma
Gumma brown tire tread that caused 7-11 team riders in Europe to crash
for lack wet traction because there was no carbon in the tread rubber.

Jobst Brandt

Per [email hidden]:

Quoted message said:

blunders such as Shimano Octalink

?
--
PeteCresswell