25.4mm handlebars w/ 26.0mm stem?

[Stephen Dimmick]

Dear rec.bicycles.tech,

Earlier today I was wondering whether or not handlebars designed for use
with smaller stem clamp diameters could safely coexist with stems with
larger stem clamp diameters. In particular, could the popular 25.4mm
handlebar diameter work safely with the dually popular 26.0mm stem
clamp?

I've read and also assumed that the reason stems are designed to
precisely match various handlebar sizes is to avoid overly bending the
stem at the clamp to compensate for smaller handlebars, and I'd imagine
that this is of particular concern when dealing with less tensile
materials such as aluminum. If this is the case, and using an aluminum
stem as an example, to what extent can a stem clamp be "safely bent"? Is
0.6mm really that significant of a difference in this scenario?

Thanks much,
--
stephen dimmick :: [email protected]

 

[MalP]

Dear rec.bicycles.tech,

Earlier today I was wondering whether or not handlebars designed for use
with smaller stem clamp diameters could safely coexist with stems with
larger stem clamp diameters. In particular, could the popular 25.4mm
handlebar diameter work safely with the dually popular 26.0mm stem
clamp?

I've read and also assumed that the reason stems are designed to
precisely match various handlebar sizes is to avoid overly bending the
stem at the clamp to compensate for smaller handlebars, and I'd imagine
that this is of particular concern when dealing with less tensile
materials such as aluminum. If this is the case, and using an aluminum
stem as an example, to what extent can a stem clamp be "safely bent"? Is
0.6mm really that significant of a difference in this scenario?

Thanks much,
--
stephen dimmick :: [email protected]

Apparently the trick is to shim it with a section of coke can (I guess pepsi works just as well, dunno). I'd confirm that with wiser sources than me though.

A little while ago, I didn't realise there was two similar handlebar diameters. I installed a set of newer bars onto and old stem and had to tighen the bolt a little more than I thought should be necessary. Seemed to work fine though, and for quite a while. On an early morning ride though, some time later, while in the drops and braking hard for a downhill corner, the stem snapped across the front of the bars. I still don't know how I didn't crash, but it got very ugly very quickly. Later inspection showed that the aluminium stem had been cracked, probably for some time. In was then a metter of when, not if, it was going to let go.

So, in answer to "Is 0.6mm really that significant of a difference in this scenario?", it sure was in my case.

 

[* * Chas]

"MalP" <[email protected]> wrote in message
news:[email protected]...
>
> Stephen Dimmick Wrote:
> > Dear rec.bicycles.tech,
> >
> > Earlier today I was wondering whether or not handlebars designed for
> > use
> > with smaller stem clamp diameters could safely coexist with stems
with
> > larger stem clamp diameters. In particular, could the popular 25.4mm
> > handlebar diameter work safely with the dually popular 26.0mm stem
> > clamp?
> >
> > I've read and also assumed that the reason stems are designed to
> > precisely match various handlebar sizes is to avoid overly bending
the
> > stem at the clamp to compensate for smaller handlebars, and I'd
> > imagine
> > that this is of particular concern when dealing with less tensile
> > materials such as aluminum. If this is the case, and using an
aluminum
> > stem as an example, to what extent can a stem clamp be "safely
bent"?
> > Is
> > 0.6mm really that significant of a difference in this scenario?
> >
> > Thanks much,
> > --
> > stephen dimmick :: [email protected]pparently the trick is to
shim it with a section of coke can (I guess
> pepsi works just as well, dunno). I'd confirm that with wiser sources
> than me though.
>
> A little while ago, I didn't realise there was two similar handlebar
> diameters. I installed a set of newer bars onto and old stem and had
to
> tighen the bolt a little more than I thought should be necessary.
Seemed
> to work fine though, and for quite a while. On an early morning ride
> though, some time later, while in the drops and braking hard for a
> downhill corner, the stem snapped across the front of the bars. I
still
> don't know how I didn't crash, but it got very ugly very quickly.
Later
> inspection showed that the aluminium stem had been cracked, probably
> for some time. In was then a metter of when, not if, it was going to
> let go.
>
> So, in answer to "Is 0.6mm really that significant of a difference in
> this scenario?", it sure was in my case.
>
>
> --
> MalP
>

What brand of stem was it that broke? Was it cast or forged aluminum?

Chas.

 

[Qui si parla Campagnolo]

Stephen Dimmick wrote:
> Dear rec.bicycles.tech,
>
> Earlier today I was wondering whether or not handlebars designed for use
> with smaller stem clamp diameters could safely coexist with stems with
> larger stem clamp diameters. In particular, could the popular 25.4mm
> handlebar diameter work safely with the dually popular 26.0mm stem
> clamp?

NO.....
>
> I've read and also assumed that the reason stems are designed to
> precisely match various handlebar sizes is to avoid overly bending the
> stem at the clamp to compensate for smaller handlebars, and I'd imagine
> that this is of particular concern when dealing with less tensile
> materials such as aluminum. If this is the case, and using an aluminum
> stem as an example, to what extent can a stem clamp be "safely bent"? Is
> 0.6mm really that significant of a difference in this scenario?
>
> Thanks much,
> --
> stephen dimmick :: [email protected]

 

[Paul Hobson]

Stephen Dimmick wrote:
> Dear rec.bicycles.tech,
>
> Earlier today I was wondering whether or not handlebars designed for use
> with smaller stem clamp diameters could safely coexist with stems with
> larger stem clamp diameters. In particular, could the popular 25.4mm
> handlebar diameter work safely with the dually popular 26.0mm stem
> clamp?

As others said, no.

> I've read and also assumed that the reason stems are designed to
> precisely match various handlebar sizes is to avoid overly bending the
> stem at the clamp to compensate for smaller handlebars, and I'd imagine
> that this is of particular concern when dealing with less tensile
> materials such as aluminum. If this is the case, and using an aluminum
> stem as an example, to what extent can a stem clamp be "safely bent"? Is
> 0.6mm really that significant of a difference in this scenario?

Yeah. You've got three options really: buy stuff that's compatible, buy
shimming material, or go with the Miller High Life/PBR can method. I
prefer PBR but High Life is better when you have to drink it warm.

Since your clearly in Atlanta, check out www.sopobikes.org and see if
you can find something that's compatible at their shop. They'll only
ask for a small donation.
\\paul

 

[Diablo Scott]

Years ago I bought a new Cinelli handlebar for a Cinelli stem that I
had. I didn't know at the time, that Cinelli had dumped it's unique
26.4mm clamp size (my existing stem) and switched to the now standard
26.0mm clamp size (my new handlebars). Installed OK and the bars seemed
secure but would rotate in the stem on big bumps so I kept tightening
the clamp until finally the bolt sheared off.

 

[* * Chas]

"Diablo Scott" <[email protected]> wrote in message
news:[email protected]...
> Years ago I bought a new Cinelli handlebar for a Cinelli stem that I
> had. I didn't know at the time, that Cinelli had dumped it's unique
> 26.4mm clamp size (my existing stem) and switched to the now standard
> 26.0mm clamp size (my new handlebars). Installed OK and the bars
seemed
> secure but would rotate in the stem on big bumps so I kept tightening
> the clamp until finally the bolt sheared off.

Looking at the latest Cinelli catalog, they still list the old 1/A stems
and they still take a 26.4mm bar while the rest of their stems fit 26mm
bars.

Chas.

 

[Werehatrack]

On Mon, 2 Oct 2006 03:21:03 +0000 (UTC), Stephen Dimmick
<[email protected]> wrote:

>Dear rec.bicycles.tech,
>
>Earlier today I was wondering whether or not handlebars designed for use
>with smaller stem clamp diameters could safely coexist with stems with
>larger stem clamp diameters. In particular, could the popular 25.4mm
>handlebar diameter work safely with the dually popular 26.0mm stem
>clamp?

It's been done. Wrap a slice of cola can around the bar; you may need
two thicknesses, but one sometimes does the trick. The best idea is
to use part that match to begin with; every layer added is another
place for a failure to occur.

>I've read and also assumed that the reason stems are designed to
>precisely match various handlebar sizes is to avoid overly bending the
>stem at the clamp to compensate for smaller handlebars, and I'd imagine
>that this is of particular concern when dealing with less tensile
>materials such as aluminum.

Maybe, but it's just as likely that the reason for the varying
diameters lies with somebody in a given company deciding that they
want the consumers to be obligated (for a while) to buy both the bars
and the stem from the same source.

>If this is the case, and using an aluminum
>stem as an example, to what extent can a stem clamp be "safely bent"?

It's a really bad idea to do it this way. In some cases it may appear
to work, but you will make the clamp slightly oval in the process; not
a good thing. Use a shim if you can't use parts that are designed to
work correctly. Either way, match the item being clamped to the size
of the clamp so that the gripping occurs as it was designed to.

>Is
>0.6mm really that significant of a difference in this scenario?

Yes. That's nearly 2mm of difference in circumference; some clamps
don't have 2mm of gap left when properly tightened.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

 

[Stephen Dimmick]

Paul Hobson <[email protected]> wrote:
> Stephen Dimmick wrote:
>> Dear rec.bicycles.tech,
>>
>> Earlier today I was wondering whether or not handlebars designed for use
>> with smaller stem clamp diameters could safely coexist with stems with
>> larger stem clamp diameters. In particular, could the popular 25.4mm
>> handlebar diameter work safely with the dually popular 26.0mm stem
>> clamp?
>
> As others said, no.
>
>> I've read and also assumed that the reason stems are designed to
>> precisely match various handlebar sizes is to avoid overly bending the
>> stem at the clamp to compensate for smaller handlebars, and I'd imagine
>> that this is of particular concern when dealing with less tensile
>> materials such as aluminum. If this is the case, and using an aluminum
>> stem as an example, to what extent can a stem clamp be "safely bent"? Is
>> 0.6mm really that significant of a difference in this scenario?
>
> Yeah. You've got three options really: buy stuff that's compatible, buy
> shimming material, or go with the Miller High Life/PBR can method. I
> prefer PBR but High Life is better when you have to drink it warm.

Thanks, Paul. This aluminum can shimming method seems to be pretty
widely deployed! And as a side note, I'm not really planning on mixing
and matching stems and handlebars. This particular example just raised
my desire to understand exactly why such a variety of components exist
that differ in size by only a fraction of a millimeter and why two such
differently sized components should not be used together.

Before I was seriously interested in bicycles, a size difference of a
fraction of a millimeter seemed pretty inconsequential to me. Now,
however, I'm debating spending one of my computer science electives on
a materials science course!

> Since your clearly in Atlanta, check out www.sopobikes.org and see if
> you can find something that's compatible at their shop. They'll only
> ask for a small donation.

Sopo Bikes is a pretty darn cool place.

--
stephen dimmick :: [email protected]

 

[Paul Hobson]

Stephen Dimmick wrote:
> Paul Hobson <[email protected]> wrote:
>> Stephen Dimmick wrote:
>>> Dear rec.bicycles.tech,
>>>
>>> Earlier today I was wondering whether or not handlebars designed for use
>>> with smaller stem clamp diameters could safely coexist with stems with
>>> larger stem clamp diameters. In particular, could the popular 25.4mm
>>> handlebar diameter work safely with the dually popular 26.0mm stem
>>> clamp?
>> As others said, no.
>>
>>> I've read and also assumed that the reason stems are designed to
>>> precisely match various handlebar sizes is to avoid overly bending the
>>> stem at the clamp to compensate for smaller handlebars, and I'd imagine
>>> that this is of particular concern when dealing with less tensile
>>> materials such as aluminum. If this is the case, and using an aluminum
>>> stem as an example, to what extent can a stem clamp be "safely bent"? Is
>>> 0.6mm really that significant of a difference in this scenario?
>> Yeah. You've got three options really: buy stuff that's compatible, buy
>> shimming material, or go with the Miller High Life/PBR can method. I
>> prefer PBR but High Life is better when you have to drink it warm.
>
> Thanks, Paul. This aluminum can shimming method seems to be pretty
> widely deployed! And as a side note, I'm not really planning on mixing
> and matching stems and handlebars. This particular example just raised
> my desire to understand exactly why such a variety of components exist
> that differ in size by only a fraction of a millimeter and why two such
> differently sized components should not be used together.
>
> Before I was seriously interested in bicycles, a size difference of a
> fraction of a millimeter seemed pretty inconsequential to me. Now,
> however, I'm debating spending one of my computer science electives on
> a materials science course!
>
>> Since your clearly in Atlanta, check out www.sopobikes.org and see if
>> you can find something that's compatible at their shop. They'll only
>> ask for a small donation.
>
> Sopo Bikes is a pretty darn cool place.
>

Good God don't take an MSE course(snooze-fest)! I think you'd do better
with a mechanics of deformable bodies course from Larry Jacobs. But
then again, I'm biased (CE grad student)
\\paul

 

[BJaY]

> Earlier today I was wondering whether or not handlebars designed for use
> with smaller stem clamp diameters could safely coexist with stems with
> larger stem clamp diameters. In particular, could the popular 25.4mm
> handlebar diameter work safely with the dually popular 26.0mm stem
> clamp?
>
> I've read and also assumed that the reason stems are designed to
> precisely match various handlebar sizes is to avoid overly bending the
> stem at the clamp to compensate for smaller handlebars, and I'd imagine
> that this is of particular concern when dealing with less tensile
> materials such as aluminum. If this is the case, and using an aluminum
> stem as an example, to what extent can a stem clamp be "safely bent"? Is
> 0.6mm really that significant of a difference in this scenario?
>
> Thanks much,
> --

Thought I'd highjack this thread to tell you of an experience I had today.
I've recently been doing a major overhall and decided to re-angle my drops
so they were more comfortable for about town stuff. I couldn't get them to
stay at the angle I wanted and so stuffed a bit of rubber in the clamp to
get a firmer grip. The handlebars snapped on one side today (they broke
'slowwwllyyy' so I'm OK), though it's clear there has been a big crack for
some time. The parts in question are ITM Liner 100 stem and SR Road champion
SAKAE custom. Anybody got any idea on what sizes these parts are and what I
should replace the bars with. Also, during the overhall, the stem had to be
'persuaded' to leave the forks with a hammer. It looks like a tough stem but
my whole attitude to aluminium is changing rapidly.

Thanks for any help.

Bruce.

 

[Marcus Coles]

BJaY wrote:

>
> Thought I'd highjack this thread to tell you of an experience I had today.
> I've recently been doing a major overhall and decided to re-angle my drops
> so they were more comfortable for about town stuff. I couldn't get them to
> stay at the angle I wanted and so stuffed a bit of rubber in the clamp to
> get a firmer grip. The handlebars snapped on one side today (they broke
> 'slowwwllyyy' so I'm OK), though it's clear there has been a big crack for
> some time. The parts in question are ITM Liner 100 stem and SR Road champion
> SAKAE custom. Anybody got any idea on what sizes these parts are and what I
> should replace the bars with. Also, during the overhall, the stem had to be
> 'persuaded' to leave the forks with a hammer. It looks like a tough stem but
> my whole attitude to aluminium is changing rapidly.
>
> Thanks for any help.
>
> Bruce.
>
>
FWIW any SR Road Champion bars I have seen have been 25.4 diameter.
I would also guess that they are at least 20 years old, so they were
good while they lasted.
These are not light weight bars and unless they had seen a lot of use I
would guess that they started to fail at a scratch or gouge.

I would guess the stem is probably of newer vintage and 26.0mm clamp
diameter.

Marcus