Why using this small spacer on the top of the stem (Team Emirates)?

Discuss light weight issues concerning road bikes & parts.
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Calnago
Posts: 6381
Joined: Sun Nov 07, 2010 9:14 pm

by Calnago

wilwil wrote:
Wed May 16, 2018 3:50 pm
Calnago wrote:
Wed May 16, 2018 3:31 pm
wilwil wrote:
Cemicar wrote:
Sun May 13, 2018 11:20 am
I think this has been suggested by bike manufactures, besides stem suppliers such as Deda.

Here is what Bianchi said for instance.

https://www.bianchi.com/global/news/new ... ty-warning

Why would a possible wear or cut mark from the lower edge of the stem only be there if the stem had had spacers of more than 5mm above it?
It goes back to what was being said earlier... and relates to where the interenal expansion plug ends up being. In lots of cases the expansion plug is quite short and is designed to be positioned in a very specific spot within the steertube, and most typically wants to support the lower bolt area and the lower edge of the stem where it meets the steertube. If you throw too many spacers above the steertube that means the expansion plug also is positioned higher (also depends on the plugs design as well). This it may provide an anchor to provide the preload on the headset still, but it no longer is providing the structural support that it is intended to provide. And every system is different these days, some don’t even use an extremely an expansion plug. Best advice if you’re not sure is to follow the manufacturers recommendations.
I understand that, but how deep the plug goes won't effect cut marks happening on the outside face of the steerer as mentioned in the Bianchi warning. I have seen such marks and put it down to over sharp edges on stem or spacers.
Cutting the steerer as short as possible makes the frame much harder to sell or adjust if you need to change your position. I usually have 10-15mm spacer above and make sure the bung is deep enough. Doesn't look as nice though. Canyons and C59s came with Acoss headsets that have no bung.
Well, any "sharp" edges on stems should really be removed if you're using them on a carbon steerer, because yes, they could very well "mark" up the steertube, and if they score it, could create a very dangerous stress riser and that's what the Bianchi warning is concenred about. Consdier the force when you are braking and a lot of your weight is on the bars. That force would like to snap that steertube right at the base of the stem, or the upper headset bearing. Without the underlying support in that area that the expander plug provides, the lower edge of the stem can certainly want to gouge into the front of the steertube where it meets at the lower lip. With the plug in there, you could still potentially overtighten the stem and gouge the steertube a bit (hopefully you don't), but the added support will go a long ways towards preventing it from actually snapping at that point. And again, depends on how the whole thing is designed... some, like Canyon as you mention, do not even have a plug in there. But the C59's absolutely do, a very long one.

If you want to leave a bunch of steertube on top for resale purposes, well that's a different thing. Just make sure if the bung is intended to be in a certain place that it ends up in that place regardless of how big a knob you want to leave on top. But really... I think anything more than a centimeter starts looking really hideous, unless you're still in the process of deciding where you want it to be cut. I guess I don't worry about setting up a bike for the next "potential" owner, but to each his own.
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Jengaback
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by Jengaback

With regards to the Bianchi statement I think that was related to issues they had with the forks on the Infinito. They ended up sending out replacements as it was found to be a manufacturing issue.

Despite that, I am always on the side of a 5 or 3mm (if I can find one) spacer above the stem. My one exception is for single bolt stems like the 3T ARX where the clamp is so far from the top of the stem that its inconsequential

by Weenie


TobinHatesYou
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Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

Jengaback wrote:
Wed May 16, 2018 6:53 pm
With regards to the Bianchi statement I think that was related to issues they had with the forks on the Infinito. They ended up sending out replacements as it was found to be a manufacturing issue.

Despite that, I am always on the side of a 5 or 3mm (if I can find one) spacer above the stem. My one exception is for single bolt stems like the 3T ARX where the clamp is so far from the top of the stem that its inconsequential

The example on the Bianchi site shows 2cm of spacers above the stem, which I guess could be an issue with short compression plugs.

pdlpsher1
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Location: CO

by pdlpsher1

rgamble wrote:
Wed May 16, 2018 4:51 pm
Lets say for whatever reason the steertube is cut even with the top of the stem, you want the top cap to sit flush & you want peace of mind.

When setting the preload sit a 5mil spacer on top, do the adjustment, tighten the stem bolt(s), remove to spacer, and place the top cap.

A thin cap like Extralight (with a hollow 3mil titanium bolt) works well.
I have the impression that if you do it this way, you will eventually lose the headset bearing preload after riding on some very bumpy roads. Do you recall the Sagan loose stem bolt incident at the PB this year?

I wouldn't be surprised that some extreme WWs would even go as far as removing the bung entirely after setting the preload :unbelievable:

jeanjacques
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Joined: Thu Apr 14, 2016 11:01 am
Location: France

by jeanjacques

pdlpsher1 wrote:
Wed May 16, 2018 8:25 pm
I wouldn't be surprised that some extreme WWs would even go as far as removing the bung entirely after setting the preload :unbelievable:
Does it change something with all this light 10mm expander plug ? I'm with one of them but now I'm considering something longer (difficult to find).
After some research, it seem there is a whole bunch of problem with misplaced plug and carbon steerer, lot of brand alert report, etc.

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wheelbuilder
Posts: 478
Joined: Wed Feb 08, 2017 2:10 am

by wheelbuilder

jeanjacques wrote:
Thu May 17, 2018 12:22 am
pdlpsher1 wrote:
Wed May 16, 2018 8:25 pm
I wouldn't be surprised that some extreme WWs would even go as far as removing the bung entirely after setting the preload :unbelievable:
Does it change something with all this light 10mm expander plug ? I'm with one of them but now I'm considering something longer (difficult to find).
After some research, it seem there is a whole bunch of problem with misplaced plug and carbon steerer, lot of brand alert report, etc.
Using light/small compression plugs that don't have a lot of bite usually results in a plug that keeps moving up in the steerer over time. You set your preload and the top cap bolt pulls the compression plug up slightly. Feels loose so you do it again and it pulls it up again........repeat.

pdlpsher1
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Location: CO

by pdlpsher1

There are many reasons why a light and short expansion plug is not the most prudent WW part. I’m not taking my chances. Here are two very good videos explaining the reasons.

https://m.youtube.com/watch?reload=9&v=l2PMfPiy90E

https://m.youtube.com/watch?v=8bSnbjHiFXc


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guyc
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Location: Hampshire, England
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by guyc

There's saving weight, and then there's idiocy.

Using the wrong expansion plug to save a few grams is the latter.

wilwil
Posts: 177
Joined: Thu Sep 23, 2010 5:47 pm

by wilwil

Calnago wrote:
Wed May 16, 2018 6:18 pm
wilwil wrote:
Wed May 16, 2018 3:50 pm
Calnago wrote:
Wed May 16, 2018 3:31 pm
wilwil wrote:
Why would a possible wear or cut mark from the lower edge of the stem only be there if the stem had had spacers of more than 5mm above it?
It goes back to what was being said earlier... and relates to where the interenal expansion plug ends up being. In lots of cases the expansion plug is quite short and is designed to be positioned in a very specific spot within the steertube, and most typically wants to support the lower bolt area and the lower edge of the stem where it meets the steertube. If you throw too many spacers above the steertube that means the expansion plug also is positioned higher (also depends on the plugs design as well). This it may provide an anchor to provide the preload on the headset still, but it no longer is providing the structural support that it is intended to provide. And every system is different these days, some don’t even use an extremely an expansion plug. Best advice if you’re not sure is to follow the manufacturers recommendations.
I understand that, but how deep the plug goes won't effect cut marks happening on the outside face of the steerer as mentioned in the Bianchi warning. I have seen such marks and put it down to over sharp edges on stem or spacers.
Cutting the steerer as short as possible makes the frame much harder to sell or adjust if you need to change your position. I usually have 10-15mm spacer above and make sure the bung is deep enough. Doesn't look as nice though. Canyons and C59s came with Acoss headsets that have no bung.
Well, any "sharp" edges on stems should really be removed if you're using them on a carbon steerer, because yes, they could very well "mark" up the steertube, and if they score it, could create a very dangerous stress riser and that's what the Bianchi warning is concenred about. Consdier the force when you are braking and a lot of your weight is on the bars. That force would like to snap that steertube right at the base of the stem, or the upper headset bearing. Without the underlying support in that area that the expander plug provides, the lower edge of the stem can certainly want to gouge into the front of the steertube where it meets at the lower lip. With the plug in there, you could still potentially overtighten the stem and gouge the steertube a bit (hopefully you don't), but the added support will go a long ways towards preventing it from actually snapping at that point. And again, depends on how the whole thing is designed... some, like Canyon as you mention, do not even have a plug in there. But the C59's absolutely do, a very long one.

If you want to leave a bunch of steertube on top for resale purposes, well that's a different thing. Just make sure if the bung is intended to be in a certain place that it ends up in that place regardless of how big a knob you want to leave on top. But really... I think anything more than a centimeter starts looking really hideous, unless you're still in the process of deciding where you want it to be cut. I guess I don't worry about setting up a bike for the next "potential" owner, but to each his own.
The C59 shipped with an Acoss headset in the UK which just has a thin alu tube that sits in the top of the steerer. I changed mine to a C60 headset.

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Calnago
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by Calnago

@wilwil: When Colnago switched to Acros for their headsets, there was a brief period where they used that really dumb design where the headset cover was a two piece wedge affair with a tiny bolt that was supposed to keep the two halves of the wedge securely “squeezed” between the top of the headset bearing and the secured stem. This is how the preload was adjusted and the top cap and insert provided no preload at all but it was still there if I’m not mistaken, and I could be. So if they tried to follow the Canyon model briefly I’m unaware of it. Anyway, their use of that design was very short lived as of course the wedges would work themselves loose and you’d have a sloppy headset in need of constant readjustment. Got a pic of the thin alloy insert you’re referring to? Did it at least provide support at the stem clamping area to prevent crushing etc? I just can’t recall any of their systems that haven’t used a fairly long insert in the steertube. I do remember that Acros wedge affair however, and never liked it from the get go, so was glad to see it gone after basically one year, if that.
They are still using Acros headsets by the way, and they seem very good. It was just that one design that left a lot to be desired.
Colnago C64 - The Naked Build; Colnago C60 - PR99; Trek Koppenberg - Where Emonda and Domane Meet;
Unlinked Builds (searchable): Colnago C59 - 5 Years Later; Trek Emonda SL Campagnolo SR; Special Colnago EPQ

thePrince
Posts: 118
Joined: Sun Jun 16, 2013 1:09 am

by thePrince

pdlpsher1 wrote:
Wed May 16, 2018 8:25 pm
rgamble wrote:
Wed May 16, 2018 4:51 pm
Lets say for whatever reason the steertube is cut even with the top of the stem, you want the top cap to sit flush & you want peace of mind.

When setting the preload sit a 5mil spacer on top, do the adjustment, tighten the stem bolt(s), remove to spacer, and place the top cap.

A thin cap like Extralight (with a hollow 3mil titanium bolt) works well.
I have the impression that if you do it this way, you will eventually lose the headset bearing preload after riding on some very bumpy roads. Do you recall the Sagan loose stem bolt incident at the PB this year?

I wouldn't be surprised that some extreme WWs would even go as far as removing the bung entirely after setting the preload :unbelievable:
Yeah there is nothing gained by this bait and switch method. TBH I can't believe there is this much discussion on this topic.

2.5 or 5mm spacer on top of stem to ensure the stem is 100% grabbing the steerer (and the stem bolts are not crushing the top of the steerer if you have a recessed plug). The spacer should stick over the top of the fork about 1.5mm to ensure the top cap can sit recessed below the spacer but not on top of the lip of the fork in order for it to do its job - preload.

To be really, really clear tightening the stem bolts should always be AFTER you complete the headset preload. Those bolts are there to keep the stem from rotating on the steerer, not to lock in the preload.

wilwil
Posts: 177
Joined: Thu Sep 23, 2010 5:47 pm

by wilwil

Calnago wrote:
Thu May 17, 2018 4:01 pm
@wilwil: When Colnago switched to Acros for their headsets, there was a brief period where they used that really dumb design where the headset cover was a two piece wedge affair with a tiny bolt that was supposed to keep the two halves of the wedge securely “squeezed” between the top of the headset bearing and the secured stem. This is how the preload was adjusted and the top cap and insert provided no preload at all but it was still there if I’m not mistaken, and I could be. So if they tried to follow the Canyon model briefly I’m unaware of it. Anyway, their use of that design was very short lived as of course the wedges would work themselves loose and you’d have a sloppy headset in need of constant readjustment. Got a pic of the thin alloy insert you’re referring to? Did it at least provide support at the stem clamping area to prevent crushing etc? I just can’t recall any of their systems that haven’t used a fairly long insert in the steertube. I do remember that Acros wedge affair however, and never liked it from the get go, so was glad to see it gone after basically one year, if that.
They are still using Acros headsets by the way, and they seem very good. It was just that one design that left a lot to be desired.
Its the tiny bolt (Torx 3 I think) design Im talking about, the same as Canyon use (my wife's Canyon has it). There's no need for a long expanding plug. I think the thin alloy insert does provide some support because its harder to remove once the stem has been tightened. But nothing like the massive expansion plug that ships with the C60.

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Calnago
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by Calnago

thePrince wrote:...
To be really, really clear tightening the stem bolts should always be AFTER you complete the headset preload. Those bolts are there to keep the stem from rotating on the steerer, not to lock in the preload.
Well, this topic always comes up from time to time. And of course it should be obvious to anyone that the preload needs to be set BEFORE tightening the stem bolts to the steerer (with a few exceptions such as the Acros wedge system mentioned above and some others I can think of) but I appreciate that is not always obvious to everyone. In fact, the stem bolts should be very loose when applying the preload so as to allow a smooth and progressive movement. But once the preload is set, tightening the stem bolts does indeed “lock” it in. At that point you could remove the top cap and toss it if you like. It’s purpose (to adjust the preload) is done. Really basic stuff here, but even reading some of the posts in this thread it is clear that all is not obvious. And it’s a fairly important part of any bike assembly, like... really important.
Colnago C64 - The Naked Build; Colnago C60 - PR99; Trek Koppenberg - Where Emonda and Domane Meet;
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thePrince
Posts: 118
Joined: Sun Jun 16, 2013 1:09 am

by thePrince

Calnago wrote:
Thu May 17, 2018 5:15 pm
thePrince wrote:...
To be really, really clear tightening the stem bolts should always be AFTER you complete the headset preload. Those bolts are there to keep the stem from rotating on the steerer, not to lock in the preload.
...But once the preload is set, tightening the stem bolts does indeed “lock” it in. At that point you could remove the top cap and toss it if you like. It’s purpose (to adjust the preload) is done...
I don't agree that you could just toss the top cap. I understand in theory why are you saying that. But what happens if one of the bolts on the stem is torqued incorrectly, or backs out slightly over time, etc. Now not only do you have stem that is rotating on your steerer, but you have lost ALL preload. That would be catostrophic in my opinion. Can you imagine that happening on a descent and hitting a large pothole? So the top cap is not disposable. Between the stem and top cap you should have a 2x failsafe that you aren't going to lose all preload. Should result in some creaking at worse and easily fixed by loosening the stem bolts, tightening your top cap, and then tightening the stem bolts.

Not to mention if you didn't have a top cap and you lost your preload as mentioned above during a ride how would you get home? I'm going to keep my top cap :D

by Weenie


thePrince
Posts: 118
Joined: Sun Jun 16, 2013 1:09 am

by thePrince

And one more thing re the top cap. The steerer is made to carry the compression load vertically. If you remove the top cap and apply all of the load through the stem, you would eventually delimante your steerer (vibratations and movements from the handlebar naturally causing that shear load if no vertical compression).

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