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2 bolt vs 4 bolt stems



 
 
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  #1  
Old December 20th 05, 10:34 PM posted to rec.bicycles.tech
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Default 2 bolt vs 4 bolt stems

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


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  #2  
Old December 21st 05, 06:27 AM posted to rec.bicycles.tech
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Default 2 bolt vs 4 bolt stems

On Tue, 20 Dec 2005 13:34:49 -0800, "G.T."
wrote:

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.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.
  #3  
Old December 21st 05, 07:26 AM posted to rec.bicycles.tech
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Default 2 bolt vs 4 bolt stems

Greg T? writes:

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 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
  #4  
Old December 21st 05, 08:16 AM posted to rec.bicycles.tech
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Default 2 bolt vs 4 bolt stems

G.T. wrote:
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


  #5  
Old December 21st 05, 12:11 PM posted to rec.bicycles.tech
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Default 2 bolt vs 4 bolt stems


"Werehatrack" wrote in message
news
On Tue, 20 Dec 2005 13:34:49 -0800, "G.T."
wrote:

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.



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


  #6  
Old December 21st 05, 06:46 PM posted to rec.bicycles.tech
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Default 2 bolt vs 4 bolt stems

On Wed, 21 Dec 2005 12:11:49 +0100, "Lou Holtman"
wrote:


"Werehatrack" wrote in message
news

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.
  #7  
Old December 21st 05, 06:53 PM posted to rec.bicycles.tech
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Posts: n/a
Default 2 bolt vs 4 bolt stems

Phil Lee writes:

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?


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.

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
  #8  
Old December 22nd 05, 03:19 AM posted to rec.bicycles.tech
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Default 2 bolt vs 4 bolt stems

On Wed, 21 Dec 2005 17:46:23 GMT, Werehatrack
wrote:

On Wed, 21 Dec 2005 12:11:49 +0100, "Lou Holtman"
wrote:


"Werehatrack" wrote in message
news

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.


  #9  
Old December 22nd 05, 04:05 AM posted to rec.bicycles.tech
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Posts: n/a
Default 2 bolt vs 4 bolt stems

Werehatrack wrote:

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.

  #10  
Old December 22nd 05, 05:08 AM posted to rec.bicycles.tech
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Default 2 bolt vs 4 bolt stems

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


 




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