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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
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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
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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
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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
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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
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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
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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
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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
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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
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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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