What is a headtube extension on a build sheet?

[echappist]

Specifically, in reference to Headtube (include Extensions). What is this "extension" in the build sheet? Picture from a for sale thread by a fellow forumite

Also, I'm looking at a frame with a 2 cm extension. How does that affect things?

https://forums.thepaceline.net/attachment.php?attachmentid=1698005336&d=1596143082

[ridethecliche]

I believe it means that the headtube extends 2cm above where it normally would for that frame, i.e. you can have the bars higher by 2 cm because there's a limit to how many spacers you should have on a steerer tube.

So this will protrude up an additional 2cm from where it would usually end just above the TT.

[ERK55]

On my most recent custom build the headtube extension simply meant the length of headtube above the top tube.
(Otherwise “extension” would imply there’s some standard length, which there isn’t).

[ERK55]

And it seems some builders prefer little headtube extension, particularly with lugged construction. With welded frames (think Pegoretti) the average headtube extension is often substantially more.

[echappist]

I believe it means that the headtube extends 2cm above where it normally would for that frame, i.e. you can have the bars higher by 2 cm because there's a limit to how many spacers you should have on a steerer tube.

So this will protrude up an additional 2cm from where it would usually end just above the TT.

That sounds reasonable.

So i guess something like this (https://www.ticycles.com/store-all/head-tube-extension-titanium)?

https://images.squarespace-cdn.com/content/v1/576db62a725e2552c362fdba/1482539305020-3TT0AY1QQ2DU408CDRQ6/ke17ZwdGBToddI8pDm48kL3VKmwKI3leYB51VJjLFB8UqsxRUq qbr1mOJYKfIPR7LoDQ9mXPOjoJoqy81S2I8N_N4V1vUb5AoIII bLZhVYxCRW4BPu10St3TBAUQYVKcgK5SGg9Ovb1yloBBOHcruw _mYLfAhRzzgArFCB07Dw0L8n4JypuoE5Tg6Wg5Oyvs/TCF-heads-up-extension+%283%29.JPG?format=1500w

[jtbadge]

That sounds reasonable.

So i guess something like this (https://www.ticycles.com/store-all/head-tube-extension-titanium)?


If it's specified on the frame build sheet, it is far more likely that the actual headtube is longer, not a pressed in extension.

[charliedid]

That sounds reasonable.

So i guess something like this (https://www.ticycles.com/store-all/head-tube-extension-titanium)?

https://images.squarespace-cdn.com/content/v1/576db62a725e2552c362fdba/1482539305020-3TT0AY1QQ2DU408CDRQ6/ke17ZwdGBToddI8pDm48kL3VKmwKI3leYB51VJjLFB8UqsxRUq qbr1mOJYKfIPR7LoDQ9mXPOjoJoqy81S2I8N_N4V1vUb5AoIII bLZhVYxCRW4BPu10St3TBAUQYVKcgK5SGg9Ovb1yloBBOHcruw _mYLfAhRzzgArFCB07Dw0L8n4JypuoE5Tg6Wg5Oyvs/TCF-heads-up-extension+%283%29.JPG?format=1500w

Nope

Like this

[tuscanyswe]

I think in 99% of the cases it just means how long the headtube will extend above the toptube. Thats how i would interpet with no other info at least. Esp if frame was a custom frame listing all other measurements like in this build sheet. If it was a stock frame like a moots and its said 57 with 1cm headtube extension than that would be 1cm above the normal headtube measurements 57 tho.

[echappist]

Thanks everyone

Nope

Like this

interesting. In that case, in the spec-sheet I posted, what would a 0 extension mean? The headtube can't end right at the top tube

[tuscanyswe]

Thanks everyone



interesting. In that case, in the spec-sheet I posted, what would a 0 extension mean? The headtube can't end right at the top tube

If its a for sale thread dont you have a picture of it?

[echappist]

If its a for sale thread dont you have a picture of it?

this is the bike in question (note, it's not the one I'm buying, but the spec sheet does use the name naming convention)

https://forums.thepaceline.net/attachment.php?attachmentid=1698005329&d=1596142994

[tuscanyswe]

Interesting. I would have thought, just by looking at that frame, that this pic would be of a bike with a more than 0 headtube extension.

[charliedid]

I think in 99% of the cases it just means how long the headtube will extend above the toptube. Thats how i would interpet with no other info at least. Esp if frame was a custom frame listing all other measurements like in this build sheet. If it was a stock frame like a moots and its said 57 with 1cm headtube extension than that would be 1cm above the normal headtube measurements 57 tho.

It could be that....say the normal headtube is 15cm and the fit requires 17 that would equal a 2cm extension.

[echappist]

yeah, which makes it a bit difficult to suss out what is mean on the spec sheet of the bike I'm looking at.

I wouldn't actually mind if it refers to an actual press-in extension piece, but knowing would be better.

[tuscanyswe]

I cant imagone that beeing the case. Why would a custom builder cut o tube short and then put a 2cm extension piece on it?

[echappist]

I cant imagone that beeing the case. Why would a custom builder cut o tube short and then put a 2cm extension piece on it?

Yeah, it wouldn't make a lot of sense. Perhaps just a typo on Seven's end. The spec sheet for the bike i'm interested in was recently pulled, for an older bike.

Fwiw, here's what it looks like. HT indeed 12.2 as listed on the spec sheet.

[ERK55]

Again, guys- on the build sheet the term “headtube extension” is simply a term describing the length of headtube extending above the top tube. Like “bottom bracket drop” it’s a fixed number. Not an addition to the frame. Not a frame option.

[paredown]

In the Dark Ages when people built with lugs, the vertical bits on the seat tube and head tube lugs naturally set the height for both--slightly above the top tube. (Colnago Freuler frames come to mind as a case where the seat tube and head tube continued above the lugs...)

I have no idea if the tig crowd have settled on a standard that counts as a zero extension, since obviously the tubes are mitered and run past the horizontal slightly on normal frames.

We need a frame builder to set us straight..

[charliedid]

Again, guys- on the build sheet the term “headtube extension” is simply a term describing the length of headtube extending above the top tube. Like “bottom bracket drop” it’s a fixed number. Not an addition to the frame. Not a frame option.

Not true IMO

[ridethecliche]

Again, guys- on the build sheet the term “headtube extension” is simply a term describing the length of headtube extending above the top tube. Like “bottom bracket drop” it’s a fixed number. Not an addition to the frame. Not a frame option.

Go to a few custom builder sites and try to spec out a frame. There will be options for headtube extension. These are not press in like the OP posted a picture of unless that's specified, instead, it is an actual additional extension of the headtube over what it would be otherwise. The entire headtube is longer, but the part between the top tube and downtube remains fixed as changing that alters the geometry.

The picture on this page with the measuring tape show a frame with more HT above the top tube than would be expected by convention. That's the extension.

[ERK55]

Not true IMO

I’m done.
You can discuss it further with Carl Strong, Steve Hampsten, or Mike Desalvo (to name a few).

[happycampyer]

As I’ve always understood it looking at spec sheets and talking with builders, a welded frame is typically built with a certain amount of headtube above the toptube joint to allow a reinforced area for the upper headset cup. To accommodate fit, etc., it is sometimes desirable for the headtube to extend beyond that point—this is what I understand the “extension” to be. In many cases it can be cut down (e.g., if a subsequent owner doesn’t need it) and there is still enough reinforced area for the upper headset cup. For a custom frame, I think of it as a design consideration since the toptube might otherwise have a steeper slope than desired, etc. (or a “dropped” toptube à la Pegoretti to keep the toptube level).

As Björn noted, for builders with stock sizes, like Moots, it is possible to order the frame with a headtube extension over the stock dimension without incurring a custom upcharge.

[colker]

It´s so simple. It´s about ahead sets low stack. Threaded headsets have twice the stack while quill stems may extend bars even higher.
So builders compensated the ahead stem low height w/ and an extension on the head tube.

[tuscanyswe]

As I’ve always understood it looking at spec sheets and talking with builders, a welded frame is typically built with a certain amount of headtube above the toptube joint to allow a reinforced area for the upper headset cup. To accommodate fit, etc., it is sometimes desirable for the headtube to extend beyond that point—this is what I understand the “extension” to be. In many cases it can be cut down (e.g., if a subsequent owner doesn’t need it) and there is still enough reinforced area for the upper headset cup. For a custom frame, I think of it as a design consideration since the toptube might otherwise have a steeper slope than desired, etc. (or a “dropped” toptube à la Pegoretti to keep the toptube level).

As Björn noted, for builders with stock sizes, like Moots, it is possible to order the frame with a headtube extension over the stock dimension without incurring a custom upcharge.

I agree with this its just that it makes no sense when one look at the pic of the frame in question. That does not look like a zero extension headtube no matter How u slice it or perhaps that was the standard 15 years ago and i just forgot what all bikes look like..

[unterhausen]

I think this is idiosyncratic to this builder. And probably indicates that they do, indeed, have a standard head tube length. Especially since the one spec sheet lists zero, almost nobody does that if it means length beyond the top tube. That 7 picture above looks like it has welded in extensions. Probably better for longer head tube extensions.

I forget what bikecad calls the length of headtube beyond the top and down tubes. It's a setting in both cases.

[bthornt]

I'm not sure, since I'm not a builder and I have never owned a custom frame, but I think it means something like you see in this image.

[pdmtong]

the headtube extension is the amount added to the standard headtube length a builder might spec. it is to accommodate a riders need to have the bars higher. note the HT length would INCLUDE the extension amount...the extension note just tells you some of the length is above the TT

aesthetically, the most extension I would prefer is 1cm. Beyond that, I would want rather have a taller headtube. just my preference if chosing.

note larger size Pegs technically do not have headtube extensions..rather the top tube is dropped. but that is another discussion

[echappist]

Thanks to all

Just to be clear, the pictures of the larger bike (indicated as having 0 extension is not mine)

The one that I ended up getting is the one indicated as having 12.2 cm HT (including extension). This is what it looks like, along with the build spec.

https://efpjna.by.files.1drv.com/y4mneo9wmAlKfrWsV24KkkohErWkdEaKXZ7gZ3W0dOpD2zjvHb 6RcpnKuNdaM3JqAu6vGlGBG-CzQB7nduGWpjY0j5__jeRHe6P9XfIHcm2KrHHqOIlufZ5tG4bf 4p6IF1-nsP3JMgxoSaik4x7kXJ-WJv3_HEp3Rvj5WhVJcse5fESgslKrVfxLXbvMcSvGWHIGY3ITL D8sNgBBJGsJsHv4A?width=660&height=656&cropmode=none

[pdmtong]

sometimes the extension is used to allow more TT standover. perhaps this is the case on yours.

[happycampyer]

I think this is idiosyncratic to this builder. And probably indicates that they do, indeed, have a standard head tube length. Especially since the one spec sheet lists zero, almost nobody does that if it means length beyond the top tube. That 7 picture above looks like it has welded in extensions. Probably better for longer head tube extensions.

I forget what bikecad calls the length of headtube beyond the top and down tubes. It's a setting in both cases.The headtube on the Seven above is definitely all one tube. Similar to Serotta bitd, on certain, typically higher priced models, Seven machines the headtube asymmetrically. As someone from Serotta explained to me, the benefit of the asymmetric machining is that it saves weight by removing material from the front side of the tube where it isn't needed, but retains material on the back side of the tube where it adds strength, helps maintain alignment when being welded, etc. As it was explained to me, the process requires more complicated tooling, etc., which is why it isn't common. Other than Seven today, I'm not sure whether there are any other builders that go to the trouble.

[mcteague]

Here is a quick photo I took from a 2002 Seven Cycles brochure. Back then they we really touting the option.

Tim

[ridethecliche]

Bike looks great. Just make sure it'll clear atleast 25s and hopefully 28s!

[echappist]

The headtube on the Seven above is definitely all one tube. Similar to Serotta bitd, on certain, typically higher priced models, Seven machines the headtube asymmetrically. As someone from Serotta explained to me, the benefit of the asymmetric machining is that it saves weight by removing material from the front side of the tube where it isn't needed, but retains material on the back side of the tube where it adds strength, helps maintain alignment when being welded, etc. As it was explained to me, the process requires more complicated tooling, etc., which is why it isn't common. Other than Seven today, I'm not sure whether there are any other builders that go to the trouble.

Here is a quick photo I took from a 2002 Seven Cycles brochure. Back then they we really touting the option.

Tim

Thank you both. That was quite informative

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Bike looks great. Just make sure it'll clear atleast 25s and hopefully 28s!

Thanks. 25s are fine, and really hoping that 28s work as well.

[Pegoready]

As long as you're good with the total HT length and standover height, head tube extension is completely, 100% not important unless you're hung up on aesthetics.

The head tube extension is included in the total head tube length for builders, so if you want a total 13.0 cm head tube length it does not matter if it's achieved with 0 extension or 5 cm of extension. This assumes you're good with the standover in both cases.

I think of HT ext. as one way to achieve a desired HT length. Say you want a bike with a 19 cm HT. Pegoretti would build a non-sloping 58 cm seat tube frame with a lot of extension. A builder like Potts might slope the top tube 10 degrees and build it with 0 extension and start the seat tube at 48 cm. Both frames would fit the same.

[tuscanyswe]

Considering this bike in link below has a 1.5 cm headtube extension and is also a seven yet look to have less headtube above the tt than the one we are discussing id say seven somewhere a long the line Changed the meaning (Base value / default) setting.

I guess now it means what is more logical. that the headtube extension total length above tt is listed as the extension. Which makes more sense than to have pictures of what 2cm headtube extension means only to show that a 2cm extension means 2cm more than Our normal value which is actually a total of 4cm extending over the toptube.. Thats not a good way to go about it imo esp since there is no industri standard.


https://forums.thepaceline.net/showthread.php?t=257426

[FlashUNC]

My Della Santa has a small headtube extension that Roland built it more for long-term ownership than any immediate fit need. But it's brazed in, not added in as an adapter.

And agreed with all the others, it's more in reference to the length of the final HT rather than some add-on.

[uber]

I would rather have a 2cm head tube extension than 2 cm of spacers any day.

[mcteague]

I would rather have a 2cm head tube extension than 2 cm of spacers any day.

Pretty sure that was the reason for them being offered. These are, after all, custom bikes.

Tim

[weisan]

https://roadbikeaction.com/wp-content/uploads/2018/08/Pegoretti_logo.jpg

[happycampyer]

Pretty sure that was the reason for them being offered. These are, after all, custom bikes.

TimExactly. And as I tried to explain but Pegoready did a better job of, instead of 2cm of spacers or a 2cm headtube extension, the builder could build the frame with the same, taller headtube but no extension, but then the toptube might have an odd amount of slope in order for the frame to have a reasonable amount of seatpost exposed.

[charliedid]

This thread s so weird.

[colker]

Thanks to all

Just to be clear, the pictures of the larger bike (indicated as having 0 extension is not mine)

The one that I ended up getting is the one indicated as having 12.2 cm HT (including extension). This is what it looks like, along with the build spec.

It has the stack and reach of a 52cm road bike. It should work just like a standard 52cm.

[weisan]

This thread s so weird.

whoa whoa, wait a freakin' minute, you can't use that line, it's copyright!

https://www.beatdom.com/wp-content/uploads/2016/12/beatnik.png

[ERK55]

Here is a quick photo I took from a 2002 Seven Cycles brochure. Back then they we really touting the option.

Tim

And, I rest my case.

[charliedid]

whoa whoa, wait a freakin' minute, you can't use that line, it's copyright!

https://www.beatdom.com/wp-content/uploads/2016/12/beatnik.png

:hello:

[charliedid]

And, I rest my case.

See I rest my case....we were in agreement the entire time for cripes sake.