Carbon Steerer - cut tube or spacers above stem?
#1
Senior Member
Thread Starter
Join Date: Aug 2009
Location: Minneapolis
Posts: 5,750
Bikes: 2022 Salsa Beargrease Carbon Deore 11, 2020 Salsa Warbird GRX 600, 2020 Canyon Ultimate CF SLX disc 9.0 Di2, 2020 Catrike Eola, 2016 Masi cxgr, 2011, Felt F3 Ltd, 2010 Trek 2.1, 2009 KHS Flite 220
Mentioned: 20 Post(s)
Tagged: 0 Thread(s)
Quoted: 4367 Post(s)
Liked 3,001 Times
in
1,854 Posts
Carbon Steerer - cut tube or spacers above stem?
This is kind of a complicated story, but I'll try to leave out the parts that aren't directly related to my question.
The carbon steering tube of my 7 year old Felt cracked. The crack was underneath the stem.
Felt is supplying a new fork and it is my understanding from the LBS that they won't charge for it. That's very nice.
The LBS and Felt had an extended discussion about the cause, including sharing photos, and some of this information was relayed to me second hand by the LBS mechanic.
Felt noted that there was a spacer above the stem, and, I am told "disapproved", indicating that this over the long term can place undue stress on the steering tube.
(It is not clear that this was the cause of the failure in my case. There are other possibilities but they are besides the point of my question.)
When the replacement for arrives, the LBS intends to cut the steering tube so that the stem is in the correct position without a spacer above it.
This means that I or some subsequent owner could not later raise the bars without replacing the fork.
What does the BF/BM hive mind think? Is having spacers above the stem a potential cause of steering tube failure?
The carbon steering tube of my 7 year old Felt cracked. The crack was underneath the stem.
Felt is supplying a new fork and it is my understanding from the LBS that they won't charge for it. That's very nice.
The LBS and Felt had an extended discussion about the cause, including sharing photos, and some of this information was relayed to me second hand by the LBS mechanic.
Felt noted that there was a spacer above the stem, and, I am told "disapproved", indicating that this over the long term can place undue stress on the steering tube.
(It is not clear that this was the cause of the failure in my case. There are other possibilities but they are besides the point of my question.)
When the replacement for arrives, the LBS intends to cut the steering tube so that the stem is in the correct position without a spacer above it.
This means that I or some subsequent owner could not later raise the bars without replacing the fork.
What does the BF/BM hive mind think? Is having spacers above the stem a potential cause of steering tube failure?
#2
Banned
very few spacers .. max 3cm.. because its not metal , under it
But a spacer above.. maybe 5mm is so stem is fully in contact with steerer, being carbon..
the extra 5~10 mm above is for headset pre-load adjustment , underside of the cap clearance..
But a spacer above.. maybe 5mm is so stem is fully in contact with steerer, being carbon..
the extra 5~10 mm above is for headset pre-load adjustment , underside of the cap clearance..
#3
Senior Member
Join Date: Sep 2010
Location: Roswell, GA
Posts: 8,319
Bikes: '93 Trek 750, '92 Schwinn Crisscross, '93 Mongoose Alta
Mentioned: 30 Post(s)
Tagged: 0 Thread(s)
Quoted: 1438 Post(s)
Liked 1,092 Times
in
723 Posts
If having spacers above the stem cau cause failure I would be very interested to understand the mechanism. A quick online search shows many recommendations that one needs spacers above the stem.
Since it is presumably allowable to put the stem all of the way at the top of the steerer, I do not see how putting it lower, with spacers above, could be anything but equally or, more likely less, stressful.
Perhaps one or more of our mechanical engineer members will ring in.
You may be in the middle of a finger-pointing/a**-covering exercise.
Since it is presumably allowable to put the stem all of the way at the top of the steerer, I do not see how putting it lower, with spacers above, could be anything but equally or, more likely less, stressful.
Perhaps one or more of our mechanical engineer members will ring in.
You may be in the middle of a finger-pointing/a**-covering exercise.
#4
Senior Member
Interesting.
Only thing I can think of is the perhaps the depth of the starnut/anchor in the tube in relation to the stem.
Lets exaggerate the issue: what if you had say, 1 foot of tube above the stem? Not seeing how it would affect stress on the tube below the stem. Well, unless your stem was 1 ft above the headset. Sounds like Felt doing some CYA.
I'd have the LBS install the race on the fork and install myself.
I'm with you, I always leave a cm or so on top for the next guy even though there never seems to be a next guy.
Only thing I can think of is the perhaps the depth of the starnut/anchor in the tube in relation to the stem.
Lets exaggerate the issue: what if you had say, 1 foot of tube above the stem? Not seeing how it would affect stress on the tube below the stem. Well, unless your stem was 1 ft above the headset. Sounds like Felt doing some CYA.
I'd have the LBS install the race on the fork and install myself.
I'm with you, I always leave a cm or so on top for the next guy even though there never seems to be a next guy.
#5
Banned
Carbon, no star nut >>> an expansion sleeve is put in , & spread out
So, making no scratches in the carbon composite..
and then inside it is a nut like fitting .. several makers ..
a number of bad revues on buying 2nd hand carbon stuff... not a universal good.
....
So, making no scratches in the carbon composite..
and then inside it is a nut like fitting .. several makers ..
a number of bad revues on buying 2nd hand carbon stuff... not a universal good.
....
#6
Senior Member
Join Date: Jan 2013
Location: South Jersey
Posts: 2,262
Mentioned: 18 Post(s)
Tagged: 0 Thread(s)
Quoted: 713 Post(s)
Liked 796 Times
in
473 Posts
It depends on how high the spacer extends above the stem. Carbon steerer tubes need to be fully supported by the expander, in the area where the stem clamps the steerer. If the steerer extends far enough above the stem, the expander will not be supporting the clamped area of the steerer, leading to cracking and failure at the lower edge of the stem clamp. 5 - 10mm of spacer above the stem should be fine.
Likes For dsaul:
#7
Junior Member
You’ll find a lot of folks trying to get away with doing things that are contrary to manufacturer recommendations. Doesn’t make it a good idea.
Specialized also states in their carbon steerer instructions that spacers are not to be placed above the stem except for initial fitting. For permanent installation the steerer tube is to be cut to the correct length. The reason has to go with how the expansion plug is installed. Doing otherwise can lead to failure and voids the warranty. Basically there is no going back.
What I have done to drop the stem without cutting the steerer tube is to install the stem with a reverse angle. Reverse angled stems are perfectly sound and more common than you might think.
Good luck!
Specialized also states in their carbon steerer instructions that spacers are not to be placed above the stem except for initial fitting. For permanent installation the steerer tube is to be cut to the correct length. The reason has to go with how the expansion plug is installed. Doing otherwise can lead to failure and voids the warranty. Basically there is no going back.
What I have done to drop the stem without cutting the steerer tube is to install the stem with a reverse angle. Reverse angled stems are perfectly sound and more common than you might think.
Good luck!
#8
Senior Member
Join Date: Oct 2017
Location: Chapel Hill NC
Posts: 1,683
Bikes: 2000 Litespeed Vortex Chorus 10, 1995 DeBernardi Cromor S/S
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 645 Post(s)
Liked 797 Times
in
446 Posts
You're the consumer - if you want to leave some steerer above the stem for future flexibility (or lack of flexibility!), that's your prerogative, and if the shop done agree, then take your fork (which came from Felt, not the LBS) and go elsewhere. Having the steerer extend above the stem is irrelevant as there is no torque exerted on that portion of the steerer. The important thing is to have the expander plug support the portion of the steerer clamped by the stem, and the length of the extension above the stem is limited only by the length of the screw connecting the top cap to the expander plug, necessary to preload the headset bearings. Extend the steerer as long as you like, as long as you can find a sufficiently long screw.
All that being said though, I had a 10mm extension above my stem for years, for "future flexibility", until I came to the conclusion that I wasn't going to be raising the stem any time soon, nor was I planning on selling the bike ever, so I cut off the extension, and the bike looks much nicer. Sometimes it's OK to prioritize the actual now over some nebulous future - and screw "the next guy" - that'll be his issue.
All that being said though, I had a 10mm extension above my stem for years, for "future flexibility", until I came to the conclusion that I wasn't going to be raising the stem any time soon, nor was I planning on selling the bike ever, so I cut off the extension, and the bike looks much nicer. Sometimes it's OK to prioritize the actual now over some nebulous future - and screw "the next guy" - that'll be his issue.
#9
Senior Member
Felt noted that there was a spacer above the stem, and, I am told "disapproved", indicating that this over the long term can place undue stress on the steering tube.
(It is not clear that this was the cause of the failure in my case. There are other possibilities but they are besides the point of my question.)...
Having a spacer above the stem could not have caused the failure. Extra steerer tube above the stem places zero stress on the fork or the stem. Whoever 'disapproves' is simply making a poor attempt at deflecting blame.
The only downsides of having surplus steerer tube sticking out above the stem is a little extra weight, it is somewhat of a hazard to the (male) anatomy, and it looks dorky. I leave about 1cm of extra steerer above the stem, for the future flexibility of raising my stem.
In fact, it is good practice to put a 5mm spacer above the stem, held on by the top cap. Why? because it indicates to mechanics that the full width of the stem is securely clamped to the steerer tube.
I volunteer at a high volume city bike Co-op, and we see many horror shows of stems being half-way clamped onto steerer tubes. In fact every time we see a threadless system without a spacer on top, we remove the top cap to see if the stem is adequately secured to the steerer tube, or whether it is: 'hanging on by a thread'.
Carbon steerer tubes... you CANNOT install a star-nut in these. You need a carbon-specific expander system. Once the headset bearings are properly loaded, and the stem bolts secured, the expander can in fact be removed. It does NOT provide structural integrity benefit to the system. The expander and top cap ONLY exists to allow the headset bearings to be properly loaded.
#10
bike whisperer
Join Date: Dec 2009
Location: Melbourne, Oz
Posts: 9,537
Bikes: https://weightweenies.starbike.com/forum/viewtopic.php?f=10&t=152015&p=1404231
Mentioned: 15 Post(s)
Tagged: 0 Thread(s)
Quoted: 1523 Post(s)
Liked 716 Times
in
508 Posts
A well-designed expander plug should support the steerer properly against crushing force, but many are sub-par. I make sure to use good ones so I can cut the steerer level with the top of the stem. Then I countersink them and modify the top cap if necessary to sit flush.
__________________
Sheldon Brown's bike info ~~~ Park Tools repair help
Half-step triple, using double gear ~~~ 6400 STI rebuild walkthrough ~~~ Want 8/9/10s @126mm OLD? OCR. ~~~ Shimano cassette body overhaul ~~~ Ergopower Escape wear repair ~~~ PSA: drivetrain wear
List of US/Canada bike co-ops ~~~ Global list
Sheldon Brown's bike info ~~~ Park Tools repair help
Half-step triple, using double gear ~~~ 6400 STI rebuild walkthrough ~~~ Want 8/9/10s @126mm OLD? OCR. ~~~ Shimano cassette body overhaul ~~~ Ergopower Escape wear repair ~~~ PSA: drivetrain wear
List of US/Canada bike co-ops ~~~ Global list
Likes For Kimmo:
#11
Senior Member
Join Date: Aug 2005
Location: Pittsburgh, PA
Posts: 33,656
Bikes: '96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '20 Surly Midnight Special, All are 3x10. It is hilly around here!
Mentioned: 39 Post(s)
Tagged: 0 Thread(s)
Quoted: 2026 Post(s)
Likes: 0
Liked 1,095 Times
in
741 Posts
I have two bikes with all-carbon Easton forks and have cut both steerers to allow a 10 mm spacer above the stems. One bike has 49,000 miles and the other 43,000 miles with no signs of distress so I have to conclude it hasn't done any harm. I use Profile Designs expansion plugs and these support the stem quite well.
Another important thing is to tighten the stem clamp bolts to the recommended or less torque. I use a torque wrench and usually tighten them to 4 N-m which is a bit less than the recommended maximum. I expect a lot of steerer failures come from insufficient support of the stem and excessive clamp bolt torque.
Another important thing is to tighten the stem clamp bolts to the recommended or less torque. I use a torque wrench and usually tighten them to 4 N-m which is a bit less than the recommended maximum. I expect a lot of steerer failures come from insufficient support of the stem and excessive clamp bolt torque.
Last edited by HillRider; 07-01-19 at 06:29 AM. Reason: Incorrect spacer height given
#12
Senior Member
Thread Starter
Join Date: Aug 2009
Location: Minneapolis
Posts: 5,750
Bikes: 2022 Salsa Beargrease Carbon Deore 11, 2020 Salsa Warbird GRX 600, 2020 Canyon Ultimate CF SLX disc 9.0 Di2, 2020 Catrike Eola, 2016 Masi cxgr, 2011, Felt F3 Ltd, 2010 Trek 2.1, 2009 KHS Flite 220
Mentioned: 20 Post(s)
Tagged: 0 Thread(s)
Quoted: 4367 Post(s)
Liked 3,001 Times
in
1,854 Posts
This has all been very informative. This is the set up that the bike had. It had just one spacer above the stem. Too much? Really?
And btw, this was the setup from the fitting done when I bought the bike from an LBS that was/is an authorized Felt dealer. If Felt did not recommend spacers above the stem, then either the LBS didn't know or was ignoring the guidance.
And btw, this was the setup from the fitting done when I bought the bike from an LBS that was/is an authorized Felt dealer. If Felt did not recommend spacers above the stem, then either the LBS didn't know or was ignoring the guidance.
#13
FLIR Kitten to 0.05C
Join Date: Sep 2014
Location: Lincoln, Nebraska
Posts: 5,331
Bikes: Roadie: Seven Axiom Race Ti w/Chorus 11s. CX/Adventure: Carver Gravel Grinder w/ Di2
Mentioned: 30 Post(s)
Tagged: 0 Thread(s)
Quoted: 2349 Post(s)
Liked 406 Times
in
254 Posts
This has all been very informative. This is the set up that the bike had. It had just one spacer above the stem. Too much? Really?
And btw, this was the setup from the fitting done when I bought the bike from an LBS that was/is an authorized Felt dealer. If Felt did not recommend spacers above the stem, then either the LBS didn't know or was ignoring the guidance.
And btw, this was the setup from the fitting done when I bought the bike from an LBS that was/is an authorized Felt dealer. If Felt did not recommend spacers above the stem, then either the LBS didn't know or was ignoring the guidance.
For example, my Niner plug for my Niner fork advises :
A) No more than 40mm stack height
B) NO spacers above stem
C) Cut the steer 5mm below the top of the stem when installed with spacers
D) Expander plug torques to 7Nm.
#14
Newbie
Join Date: Apr 2015
Posts: 29
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 6 Post(s)
Likes: 0
Liked 7 Times
in
6 Posts
For Trek to warranty your carbon fork, you must have a spacer above and below the stem. I have three Treks with carbon forks and they all have a minimum of 5 mm above the stem. The Boone has four seasons of cyclocross with no problems.
#15
Senior Member
Thread Starter
Join Date: Aug 2009
Location: Minneapolis
Posts: 5,750
Bikes: 2022 Salsa Beargrease Carbon Deore 11, 2020 Salsa Warbird GRX 600, 2020 Canyon Ultimate CF SLX disc 9.0 Di2, 2020 Catrike Eola, 2016 Masi cxgr, 2011, Felt F3 Ltd, 2010 Trek 2.1, 2009 KHS Flite 220
Mentioned: 20 Post(s)
Tagged: 0 Thread(s)
Quoted: 4367 Post(s)
Liked 3,001 Times
in
1,854 Posts
#16
Senior Member
i have nothing to contribute that will help OP.
but I wonder how much weight is saved vs. a CF fork with AL-steerer? I have an Al steerer and first wished I'd rather have full carbon to save weight, but reading all this I'm glad i have an AL steerer.
I fiddled with the bar height many times (and ended up higher now than after the first year of riding). Had I followed the recommendation to not have any spacers above, I would have had a too short steerer now. Keep in mind finding the correct fit can take forever since the body also adapts and changes. Having future flexibility is important, not only for resale.
but I wonder how much weight is saved vs. a CF fork with AL-steerer? I have an Al steerer and first wished I'd rather have full carbon to save weight, but reading all this I'm glad i have an AL steerer.
I fiddled with the bar height many times (and ended up higher now than after the first year of riding). Had I followed the recommendation to not have any spacers above, I would have had a too short steerer now. Keep in mind finding the correct fit can take forever since the body also adapts and changes. Having future flexibility is important, not only for resale.
#17
bike whisperer
Join Date: Dec 2009
Location: Melbourne, Oz
Posts: 9,537
Bikes: https://weightweenies.starbike.com/forum/viewtopic.php?f=10&t=152015&p=1404231
Mentioned: 15 Post(s)
Tagged: 0 Thread(s)
Quoted: 1523 Post(s)
Liked 716 Times
in
508 Posts
People talk as if only one angle of stem is available, and they can't be flipped.
__________________
Sheldon Brown's bike info ~~~ Park Tools repair help
Half-step triple, using double gear ~~~ 6400 STI rebuild walkthrough ~~~ Want 8/9/10s @126mm OLD? OCR. ~~~ Shimano cassette body overhaul ~~~ Ergopower Escape wear repair ~~~ PSA: drivetrain wear
List of US/Canada bike co-ops ~~~ Global list
Sheldon Brown's bike info ~~~ Park Tools repair help
Half-step triple, using double gear ~~~ 6400 STI rebuild walkthrough ~~~ Want 8/9/10s @126mm OLD? OCR. ~~~ Shimano cassette body overhaul ~~~ Ergopower Escape wear repair ~~~ PSA: drivetrain wear
List of US/Canada bike co-ops ~~~ Global list
#18
Junior Member
How about contacting Felt Support?
While it’s possible that authorized dealers may have tech sheets and installation updates not available to the public (Specialized does this by design), Felt structural design engineers have the definitive answer to your question about your specific fork which they are likely to share with you if you ask.
It really doesn't matter how some other carbon fork/ expansion plug combination may or may not be installed. Experience counts for nothing, and what you may or may not be able to get away with counts for nothing until you have a straight answer about proper installation from the company.
You did mention that you did crack the steerer tube while it was installed the same way you propose to install it again. I’d want to be sure that spacer positioning wasn’t part of the problem.
hope it all works out.
While it’s possible that authorized dealers may have tech sheets and installation updates not available to the public (Specialized does this by design), Felt structural design engineers have the definitive answer to your question about your specific fork which they are likely to share with you if you ask.
It really doesn't matter how some other carbon fork/ expansion plug combination may or may not be installed. Experience counts for nothing, and what you may or may not be able to get away with counts for nothing until you have a straight answer about proper installation from the company.
You did mention that you did crack the steerer tube while it was installed the same way you propose to install it again. I’d want to be sure that spacer positioning wasn’t part of the problem.
hope it all works out.
#19
Senior Member
I am looking at a row of uncut forks with carbon steerers. The wall thickness of these is such that it would take immense compressive forces to crush these. Far far beyond what is reasonably necessary to hold a stem onto a fork steerer.
A well designed carbon steerer should NOT need internal reinforcement to counteract the clamping force of the stem. That would be a very poorly designed system, as there are all different forms of stems and expander plugs on the market. The chance for mechanics swapping parts, or installing the expanders in different ways over the life of a fork is basically 100%.
So back to my original point: there should be no limit on how much extra steerer is left above the stem, except for the extra weight, the dork factor, and the safety risk.
#20
Senior Member
Many modern bikes are aggressively low, while many actual riders require comfort over speed.
Just another reason to build bikes from frame up. .......
#21
Senior Member
Thread Starter
Join Date: Aug 2009
Location: Minneapolis
Posts: 5,750
Bikes: 2022 Salsa Beargrease Carbon Deore 11, 2020 Salsa Warbird GRX 600, 2020 Canyon Ultimate CF SLX disc 9.0 Di2, 2020 Catrike Eola, 2016 Masi cxgr, 2011, Felt F3 Ltd, 2010 Trek 2.1, 2009 KHS Flite 220
Mentioned: 20 Post(s)
Tagged: 0 Thread(s)
Quoted: 4367 Post(s)
Liked 3,001 Times
in
1,854 Posts
Another shot of the current setup. Really guys? That spacer above the stem caused a problem?
Last edited by MinnMan; 07-01-19 at 08:40 PM.
#22
don't try this at home.
Join Date: Jan 2006
Location: N. KY
Posts: 5,933
Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 972 Post(s)
Liked 509 Times
in
349 Posts
Structural?
So, do plugs actually support the carbon tube walls? How can a stem clamp crush the walls when the force is all the way around? I'm assuming the plug does some kind of support internally, but a badly torqued stem (too loose or way too tight) seems to be the main cause of failures. And I wonder about the sharp edge of the machining at the stem clamp circle on some stems.
A loosened stem is going to mangle the carbon even with a plug correctly installed. That's what the photos below imply. Not a crushing split, but a slow mangling of the steerer fibers as the stem gets loading from rider and road bumps.
~~~
It's interesting that some manufacturers require a spacer, while others, like Felt, prohibit it.
Back in 2017, Bianchi said: no more than 5mm above the stem. My Bianchi came with a minimalist FSA plug, not nearly as tall as the stem. I assume the 5mm limit is to avoid ignorant mechanics placing the plug too high in the steerer. My plug sits near the bottom stem bolt.
Some plugs have a lip on the top, to sit on the cut end of the steerer. Spacers above would move those upwards. See this google image search -- plug styles are hugely varied.
~~~~~~~~~~~~~~~~~~~~~~
From an old thread on another site:
I had linked the "damaged" and "not damaged" steerer photos from Bianchi, they no longer link. But an image search showed them on Bianchi Japan, so I downloaded them.
Not damaged. There's a shiny outline of the stem, just on the surface of the steerer. Looks like a 5mm spacer was above the stem, I think.
A damaged steerer. All their damage photos show the bottom, fork end of the stem crushed the steerer.
More extreme damage! A loose stem clamp? And a huge amount of spacers above, so the plug was likely located too high? I wouldn't be surprised if they had more than 40mm of spacers below the stem, too.
So, do plugs actually support the carbon tube walls? How can a stem clamp crush the walls when the force is all the way around? I'm assuming the plug does some kind of support internally, but a badly torqued stem (too loose or way too tight) seems to be the main cause of failures. And I wonder about the sharp edge of the machining at the stem clamp circle on some stems.
A loosened stem is going to mangle the carbon even with a plug correctly installed. That's what the photos below imply. Not a crushing split, but a slow mangling of the steerer fibers as the stem gets loading from rider and road bumps.
~~~
It's interesting that some manufacturers require a spacer, while others, like Felt, prohibit it.
Back in 2017, Bianchi said: no more than 5mm above the stem. My Bianchi came with a minimalist FSA plug, not nearly as tall as the stem. I assume the 5mm limit is to avoid ignorant mechanics placing the plug too high in the steerer. My plug sits near the bottom stem bolt.
Some plugs have a lip on the top, to sit on the cut end of the steerer. Spacers above would move those upwards. See this google image search -- plug styles are hugely varied.
~~~~~~~~~~~~~~~~~~~~~~
From an old thread on another site:
...a safety warning on Bianchi's global site. This has to do with possible catastrophic failure of full carbon forks with carbon steerer tubes when assembled incorrectly. I checked Bianchi USA's site and there is no such recall/warning and no mention of the issue. Additionally, I had registered my Bianchi on BianchiUSA.com (and this information was actually logged on the global site in Italy), yet I did not receive notification of the possible problem.
The main theme of the warning is that they are claiming that stems and spacers were installed incorrectly on Sempre Pros and Intensos, but not limited to these models. They state that assembling with more than a 5mm spacer above the stem can cause damage to the steerer tube.
Interestingly, when I went into the full details and instructions, they also said that a 5mm spacer was required under the stem (and not more than 35mm) and they also said that carbon assembly paste was not to be used on the steerer tube for stem installation.
~~~The main theme of the warning is that they are claiming that stems and spacers were installed incorrectly on Sempre Pros and Intensos, but not limited to these models. They state that assembling with more than a 5mm spacer above the stem can cause damage to the steerer tube.
Interestingly, when I went into the full details and instructions, they also said that a 5mm spacer was required under the stem (and not more than 35mm) and they also said that carbon assembly paste was not to be used on the steerer tube for stem installation.
I had linked the "damaged" and "not damaged" steerer photos from Bianchi, they no longer link. But an image search showed them on Bianchi Japan, so I downloaded them.
Not damaged. There's a shiny outline of the stem, just on the surface of the steerer. Looks like a 5mm spacer was above the stem, I think.
A damaged steerer. All their damage photos show the bottom, fork end of the stem crushed the steerer.
More extreme damage! A loose stem clamp? And a huge amount of spacers above, so the plug was likely located too high? I wouldn't be surprised if they had more than 40mm of spacers below the stem, too.
Last edited by rm -rf; 07-01-19 at 08:02 PM.
#24
I am potato.
Join Date: Jun 2015
Location: Pacific Northwest
Posts: 3,107
Bikes: Only precision built, custom high performance elitist machines of the highest caliber. 🍆
Mentioned: 28 Post(s)
Tagged: 0 Thread(s)
Quoted: 1783 Post(s)
Liked 1,622 Times
in
928 Posts
Would there be anything wrong with getting a longer bolt to preload bearings but still allow for proper placement of the plug in the clamp area of the stem?
I inserted a star nut about a centimeter & a half lower than intended once & the preload bolt wouldn't thread in. A longer bolt took care of the issue & I haven't thought about it since. But now I wonder.
I would think that proper placement of the plug to offset the stem compression would be the primary concern...
That being said, there are an awful lot of carbon seatposts out there with no plug. So in my mind, that calls into question the whole premise.
I inserted a star nut about a centimeter & a half lower than intended once & the preload bolt wouldn't thread in. A longer bolt took care of the issue & I haven't thought about it since. But now I wonder.
I would think that proper placement of the plug to offset the stem compression would be the primary concern...
That being said, there are an awful lot of carbon seatposts out there with no plug. So in my mind, that calls into question the whole premise.
#25
bike whisperer
Join Date: Dec 2009
Location: Melbourne, Oz
Posts: 9,537
Bikes: https://weightweenies.starbike.com/forum/viewtopic.php?f=10&t=152015&p=1404231
Mentioned: 15 Post(s)
Tagged: 0 Thread(s)
Quoted: 1523 Post(s)
Liked 716 Times
in
508 Posts
I am looking at a row of uncut forks with carbon steerers. The wall thickness of these is such that it would take immense compressive forces to crush these. Far far beyond what is reasonably necessary to hold a stem onto a fork steerer.
A well designed carbon steerer should NOT need internal reinforcement to counteract the clamping force of the stem. That would be a very poorly designed system, as there are all different forms of stems and expander plugs on the market. The chance for mechanics swapping parts, or installing the expanders in different ways over the life of a fork is basically 100%.
A well designed carbon steerer should NOT need internal reinforcement to counteract the clamping force of the stem. That would be a very poorly designed system, as there are all different forms of stems and expander plugs on the market. The chance for mechanics swapping parts, or installing the expanders in different ways over the life of a fork is basically 100%.
My theory about the deformation is that it isn't necessarily caused by overtorque, but can happen as a result of normal clamping pressure and riding loads, plus enough time. Heat cycles, too, maybe?
__________________
Sheldon Brown's bike info ~~~ Park Tools repair help
Half-step triple, using double gear ~~~ 6400 STI rebuild walkthrough ~~~ Want 8/9/10s @126mm OLD? OCR. ~~~ Shimano cassette body overhaul ~~~ Ergopower Escape wear repair ~~~ PSA: drivetrain wear
List of US/Canada bike co-ops ~~~ Global list
Sheldon Brown's bike info ~~~ Park Tools repair help
Half-step triple, using double gear ~~~ 6400 STI rebuild walkthrough ~~~ Want 8/9/10s @126mm OLD? OCR. ~~~ Shimano cassette body overhaul ~~~ Ergopower Escape wear repair ~~~ PSA: drivetrain wear
List of US/Canada bike co-ops ~~~ Global list