Shifters level
02-21-10 | 11:18 AM
#26
Thread Starter
Senior Member
Joined: Mar 2005
Posts: 545
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From: Richmond Hill, Ontario, Canada
Bikes: Cervelo S3
Stem clamped to steerer tube below the expander plug insertion depth. Bad stuff...nothing reinforcing the inside of the clamp area. Given the length of protrusion, I don't believe that there are expander plugs that actually can insert that deep that the top cap will still be able to engage.
Most manufacturers publish safety notes with CF steerers that specify how much steerer tube should protrude. Depending on the tube and the specs of the plug, it's either none, or up to about 1 cm. They are usually pretty specific about it too.
If it's an alloy steerer, it doesn't matter.
Most manufacturers publish safety notes with CF steerers that specify how much steerer tube should protrude. Depending on the tube and the specs of the plug, it's either none, or up to about 1 cm. They are usually pretty specific about it too.
If it's an alloy steerer, it doesn't matter.
02-21-10 | 12:03 PM
#27
Senior Member
Joined: Apr 2008
Posts: 5,428
Likes: 2
Bikes: Cervelo RS, Specialized Stumpjumper FSR Pro, Schwinn Typhoon, Nashbar touring, custom steel MTB
Stem clamped to steerer tube below the expander plug insertion depth. Bad stuff...nothing reinforcing the inside of the clamp area. Given the length of protrusion, I don't believe that there are expander plugs that actually can insert that deep that the top cap will still be able to engage.
Most manufacturers publish safety notes with CF steerers that specify how much steerer tube should protrude. Depending on the tube and the specs of the plug, it's either none, or up to about 1 cm. They are usually pretty specific about it too.
For safety, it's the first one that really matters. The second one only matters when the bike is being assembled: if the steerer extends too far above the top of the stem, you won't be able to pull the fork assembly tight. If you want to leave the steerer long, perhaps because you're trying to determine the exact size/placement of spacers underneath the stem, it is common practice to stack spacers on top of the excess steerer tube. As long as the steerer tube ends slightly below the top of the last spacer, you'll usually then be able to pull the fork assembly tight enough to secure the stem. This is not dangerous, provided you're smart enough not to over-tighten the expander cap to the point where the steerer tube explodes.
02-21-10 | 03:11 PM
#29
Jet Jockey
Joined: Jul 2005
Posts: 4,941
Likes: 30
From: St. Paul, MN
Bikes: Cannondale CAAD9, Ritchey Breakaway Cross, Nashbar X-frame bike, Bike Friday Haul-a-Day, Surly Pugsley.
The only thing the expander plug (or star fangled nut) does is allow you to pull the fork assembly tight while you clamp the stem to the steerer. Once the stem is clamped, it provides the force necessary to hold the fork in place. At no time should the expander plug be tightened so much that it requires a stem surrounding it to prevent the steerer tube from exploding!
You obviously have no idea what I said.
To repeat: Expander plug and cap help resist the clamping force of the stem. Resist clamping force of stem - at no point did I say that the stem somehow kept the steerer tube from exploding. Good gravy.
If you are at all familiar with the designs of certain expander plugs, you know that the entire "mechanism" is designed to help reinforce the steerer tube as well as to tension the entire assembly to the bearings.
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02-21-10 | 03:37 PM
#31
Banned
Joined: Sep 2005
Posts: 28,387
Likes: 3
From: Santa Barbara, CA
Bikes: Specialized Tarmac SL2, Specialized Tarmac SL, Giant TCR Composite, Specialized StumpJumper Expert HT
I seem to recall giving you a hard time about the angle of your bars and shifters a while back. Good to see you've finally fixed it...
02-21-10 | 04:41 PM
#32
Senior Member
Joined: Apr 2008
Posts: 5,428
Likes: 2
Bikes: Cervelo RS, Specialized Stumpjumper FSR Pro, Schwinn Typhoon, Nashbar touring, custom steel MTB
You're right: you weren't exactly clear in your initial post.
Look: if you're such a ham-fisted dunce that you're going to crush your carbon steerer unless there's an expander plug supporting it, maybe you should switch to a fork with an aluminum steerer tube. Anyone with a little sanity, or a torque wrench, shouldn't have a problem running a bit of extra steerer for a few days, week, or months.
To repeat: Expander plug and cap help resist the clamping force of the stem. Resist clamping force of stem - at no point did I say that the stem somehow kept the steerer tube from exploding. Good gravy.
02-21-10 | 05:06 PM
#33
Jet Jockey
Joined: Jul 2005
Posts: 4,941
Likes: 30
From: St. Paul, MN
Bikes: Cannondale CAAD9, Ritchey Breakaway Cross, Nashbar X-frame bike, Bike Friday Haul-a-Day, Surly Pugsley.
Look: if you're such a ham-fisted dunce that you're going to crush your carbon steerer unless there's an expander plug supporting it, maybe you should switch to a fork with an aluminum steerer tube. Anyone with a little sanity, or a torque wrench, shouldn't have a problem running a bit of extra steerer for a few days, week, or months.
No matter what the setup, all bets are off if you overtighten.
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Good night...and good luck
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02-21-10 | 05:09 PM
#34
Banned
Joined: Sep 2005
Posts: 28,387
Likes: 3
From: Santa Barbara, CA
Bikes: Specialized Tarmac SL2, Specialized Tarmac SL, Giant TCR Composite, Specialized StumpJumper Expert HT
Look: if you're such a ham-fisted dunce that you're going to crush your carbon steerer unless there's an expander plug supporting it, maybe you should switch to a fork with an aluminum steerer tube. Anyone with a little sanity, or a torque wrench, shouldn't have a problem running a bit of extra steerer for a few days, week, or months.
the recall notice emphasizes the need to exercise proper care in both the assembly and maintenance of related parts and the new 60mm-long replacement expander plug is required only to increase the margin of error, not to bring the system up to a minimum safety standard.
The service bulletin represents the company’s view of ‘best practice’ for carbon steerers and outlines several precautionary and/or corrective measures. According to Isaac International’s Dave Palk, none is individually more critical than the others though all are related to how the internal bore of the stem interacts with the steerer tube surface:
1.The lower collar of any stem used on an Isaac carbon steerer tube must be 7mm tall or more. Shallower stem collars may indent the steerer tube surface and create a dangerous stress riser even if the steerer tube clamp bolts are properly torqued.
2. Headset spacer height below the stem must be limited to no more than 30mm but should be at least 5mm. Exceeding that figure will create too long of a lever arm on the steerer tube while running no spacers at all will create undue point stress at the base of the stem. In addition, the steerer tube length should be cut such that it just slightly extends completely through the stem for maximum surface area contact.
3. All Isaac steerer tube expander plugs should be replaced with the new 60mm-tall version, which will be provided free of charge and offer additional reinforcement below the bottom edge of the stem as a redundant safety precaution. To ensure the plug extends to the correct region of the steerer tube, total stem clamp height should be no more than 45mm and a maximum of 5mm of spacer should be placed on top of the stem.
The service bulletin represents the company’s view of ‘best practice’ for carbon steerers and outlines several precautionary and/or corrective measures. According to Isaac International’s Dave Palk, none is individually more critical than the others though all are related to how the internal bore of the stem interacts with the steerer tube surface:
1.The lower collar of any stem used on an Isaac carbon steerer tube must be 7mm tall or more. Shallower stem collars may indent the steerer tube surface and create a dangerous stress riser even if the steerer tube clamp bolts are properly torqued.
2. Headset spacer height below the stem must be limited to no more than 30mm but should be at least 5mm. Exceeding that figure will create too long of a lever arm on the steerer tube while running no spacers at all will create undue point stress at the base of the stem. In addition, the steerer tube length should be cut such that it just slightly extends completely through the stem for maximum surface area contact.
3. All Isaac steerer tube expander plugs should be replaced with the new 60mm-tall version, which will be provided free of charge and offer additional reinforcement below the bottom edge of the stem as a redundant safety precaution. To ensure the plug extends to the correct region of the steerer tube, total stem clamp height should be no more than 45mm and a maximum of 5mm of spacer should be placed on top of the stem.
02-22-10 | 01:04 AM
#35
Sua Ku
Joined: Aug 2006
Posts: 5,705
Likes: 2
From: Hot as hell, Singapore
Bikes: Trek 5200, BMC SLC01, BMC SSX, Specialized FSR, Holdsworth Criterium
Stem clamped to steerer tube below the expander plug insertion depth. Bad stuff...nothing reinforcing the inside of the clamp area. Given the length of protrusion, I don't believe that there are expander plugs that actually can insert that deep that the top cap will still be able to engage.
Most manufacturers publish safety notes with CF steerers that specify how much steerer tube should protrude. Depending on the tube and the specs of the plug, it's either none, or up to about 1 cm. They are usually pretty specific about it too.
If it's an alloy steerer, it doesn't matter.
Most manufacturers publish safety notes with CF steerers that specify how much steerer tube should protrude. Depending on the tube and the specs of the plug, it's either none, or up to about 1 cm. They are usually pretty specific about it too.
If it's an alloy steerer, it doesn't matter.
I always leave 5mm on the top with all of my alloy steerers, just seemed better then compressing the very end of the steerer, no science, just old habit.
I now have a carbon steerer and do the same. I will have to check the recommendations from Easton.
Still I guess I never tighten my stem that much.
02-22-10 | 08:27 AM
#37
Senior Member
Joined: Jan 2005
Posts: 629
Likes: 10
From: Greenville, SC
Bikes: Lynskey R230, Gary Fisher Tassajara; Motobecane Boris Fatbike; Cannondale Habit
Thanks for clearing that up.
I always leave 5mm on the top with all of my alloy steerers, just seemed better then compressing the very end of the steerer, no science, just old habit.
I now have a carbon steerer and do the same. I will have to check the recommendations from Easton.
Still I guess I never tighten my stem that much.
I always leave 5mm on the top with all of my alloy steerers, just seemed better then compressing the very end of the steerer, no science, just old habit.
I now have a carbon steerer and do the same. I will have to check the recommendations from Easton.
Still I guess I never tighten my stem that much.
02-22-10 | 08:42 AM
#38
Jet Jockey
Joined: Jul 2005
Posts: 4,941
Likes: 30
From: St. Paul, MN
Bikes: Cannondale CAAD9, Ritchey Breakaway Cross, Nashbar X-frame bike, Bike Friday Haul-a-Day, Surly Pugsley.
Thanks for clearing that up.
I always leave 5mm on the top with all of my alloy steerers, just seemed better then compressing the very end of the steerer, no science, just old habit.
I now have a carbon steerer and do the same. I will have to check the recommendations from Easton.
Still I guess I never tighten my stem that much.
I always leave 5mm on the top with all of my alloy steerers, just seemed better then compressing the very end of the steerer, no science, just old habit.
I now have a carbon steerer and do the same. I will have to check the recommendations from Easton.
Still I guess I never tighten my stem that much.
However, since that version, manufacturers have come out with different forms of plugs, reinforcements, etc., and so Mr. Zinn's advice doesn't always apply anymore. One needs to read the manufacturer's instructions. Some specify x amount of spacer on top, and some specify zero, with tube cut approx 2mm below top of stem. Manufacturers will also have specified insertion depths for the plug/reinforcement that they make.
I do my alloy steerers like you do. I think it's good practice, and so does Lennard Zinn.
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Good night...and good luck
Good night...and good luck
