Reliability of Steerer Materials

John Forrest Tomlinson wrote:

On 9 Aug 2004 02:16:31 -0700, (Chalo) wrote:

John Forrest Tomlinson wrote:

I don't understand how a steerer tube can flex much at all. Do they?

Oh you bet. Sight down your fork while you grab some front brakes and
see for yourself.

I can't see that precisely due to the forces on my head and body while
braking.

I wonder how you can see that well. It doesnt' sound plausible.

You can do that while standing still.

Lou

On Mon, 09 Aug 2004 13:16:13 +0200, Lou Holtman wrote:

John Forrest Tomlinson wrote:

On 9 Aug 2004 02:16:31 -0700, (Chalo) wrote:

John Forrest Tomlinson wrote:

I don't understand how a steerer tube can flex much at all. Do they?

Oh you bet. Sight down your fork while you grab some front brakes and
see for yourself.

I can't see that precisely due to the forces on my head and body while
braking.

I wonder how you can see that well. It doesnt' sound plausible.

You can do that while standing still.

I don't understand how I can keep my head still enough to see motion
of just a few millimeters or less. Even moving my head a fraction of
an mm will put the whole thing off. If the tires compress or flex that
will also throw everything off.

If there was some sort of jig with measurement indicators, maybe this
would work. But just standing behind the bike and squeezing the brakes
does not seem precise enough.

JT

John Forrest Tomlinson wrote:

On Mon, 09 Aug 2004 13:16:13 +0200, Lou Holtman wrote:

John Forrest Tomlinson wrote:

On 9 Aug 2004 02:16:31 -0700, (Chalo) wrote:

John Forrest Tomlinson wrote:

I don't understand how a steerer tube can flex much at all. Do they?

Oh you bet. Sight down your fork while you grab some front brakes and
see for yourself.

I can't see that precisely due to the forces on my head and body while
braking.

I wonder how you can see that well. It doesnt' sound plausible.

You can do that while standing still.

I don't understand how I can keep my head still enough to see motion
of just a few millimeters or less. Even moving my head a fraction of
an mm will put the whole thing off. If the tires compress or flex that
will also throw everything off.

If there was some sort of jig with measurement indicators, maybe this
would work. But just standing behind the bike and squeezing the brakes
does not seem precise enough.

JT

Believe me the steerer tube flexes. You can easily think of a more
precise method yourself to measure this. Use your imagination.

Lou

On Mon, 09 Aug 2004 14:07:10 +0200, Lou Holtman wrote:

Believe me the steerer tube flexes.
You can easily think of a more
precise method yourself to measure this.
Use your imagination.

Have you used a precise measuring system?

If you think you can see it by eyeballing it as you suggested it's
likely that is is _your_ imagination that is producing the effect.

I'm not saying steerer tubes don't flex. I don't know if they do.

I'm just saying it sure doesn't sound like you or other people in this
thread who say they can see it are actually seeing it. It doesn't
seem possible to see something that small if your body (to which your
eyers are attached) is involved in producing the effect.

JT

John Forrest Tomlinson wrote:

On Mon, 09 Aug 2004 14:07:10 +0200, Lou Holtman wrote:

Believe me the steerer tube flexes.
You can easily think of a more
precise method yourself to measure this.
Use your imagination.

Have you used a precise measuring system?

I don't have to I can calculate how much it flexes.


If you think you can see it by eyeballing it as you suggested it's
likely that is is _your_ imagination that is producing the effect.


You can use a steady reference and a little help from a second person
who pushes the fork against a wall for instance.

I'm not saying steerer tubes don't flex. I don't know if they do.

They do.


I'm just saying it sure doesn't sound like you or other people in this
thread who say they can see it are actually seeing it. It doesn't
seem possible to see something that small if your body (to which your
eyers are attached) is involved in producing the effect.

How small do you think it is?

Lou

Lou Holtman wrote in message ...
John Forrest Tomlinson wrote:

On Mon, 09 Aug 2004 14:07:10 +0200, Lou Holtman wrote:

Believe me the steerer tube flexes.
You can easily think of a more
precise method yourself to measure this.
Use your imagination.

Have you used a precise measuring system?

I don't have to I can calculate how much it flexes.

Interesting. Not persuasive, but I guess we'll have to trust you.


If you think you can see it by eyeballing it as you suggested it's
likely that is is _your_ imagination that is producing the effect.


You can use a steady reference and a little help from a second person
who pushes the fork against a wall for instance.

Have you ever done this? Have you ever measured this effect?


I'm not saying steerer tubes don't
flex. I don't know if they do.

They do.


I'm just saying it sure doesn't sound like you or other people in this
thread who say they can see it are actually seeing it. It doesn't
seem possible to see something that small if your body (to which your
eyers are attached) is involved in producing the effect.

How small do you think it is?

I don't know, but I do know that if my eyes move a millimeter or two
it's impossible for me to say with any certainty that where/if I see
flex in a structure that includes fork blades, steerer tube and tires
unless some part is flexing, say, at least half a centimeter in some
direction. I can't conceive of how a steerer tube could flex that much
w/o some sort of binding in the headset, unless the head tube is also
flexing too. So I would speculate (again, I don't know) that the flex
(if any) is less than that. And I have no confidence I could see that
accurately.

I tried the just holding the brakes on my bike this morning and trying
to see the flex and I couldn't. I could see motion for sure, but I
couldn't tell if it was coming from my head moving, or the tires, or
the fork blade, or the steerer tube. This was with an aluminum
steerer. I've got a bike with a carbon steerer in storage I will try
later.

JT

Not all carbon is equal. Some forks are made with woven sheet that has
been rolled while others are wound and oriented. Forks made with woven
material tend to be whippy while those made with oriented fibers, like a
True Temper Alpha are incredibly stiff.

Its not all good because with the Alpha, you MUST use their adjustment
nut insert and once glued in place, recutting the fork is next to
impossible.


--
Weisse Luft

John Forrest Tomlinson wrote:

On Mon, 09 Aug 2004 14:07:10 +0200, Lou Holtman wrote:

Believe me the steerer tube flexes.
You can easily think of a more
precise method yourself to measure this.
Use your imagination.

Have you used a precise measuring system?

It's not a precision quantity in question; it's big. Tandems have
been known to generate braking forces that flex the fork back enough
for the front tire to scuff the downtube, *without* permanently
bending the fork. As I said before, I have bent many fork steerers
myself, and CrMo steel does not yield before first flexing deeply.

You must be exceedingly lightweight if you have not perceived steer
tube flex in your own bike. Even then you must be noticing something,
but attributing it to some other cause.

Chalo Colina

Weisse Luft wrote in message ...
Not all carbon is equal. Some forks are made with woven sheet that has
been rolled while others are wound and oriented. Forks made with woven
material tend to be whippy while those made with oriented fibers, like a
True Temper Alpha are incredibly stiff.

Its not all good because with the Alpha, you MUST use their adjustment
nut insert and once glued in place, recutting the fork is next to
impossible.

You can re-cut the fork. Max length reduction due to glued in insert
is 2 cm. The fork probably will transfer fine between *your* frame
and frames of similar dimension.

Cutting through the extra aluminum of the insert and epoxy is not
"next to impossible".

That said, any of the Ouzo's is much easier to deal with in this
regard. And no steerer tube can be made longer once it is cut.

App

On 2004-08-08 00:57:37 -0700, "D. Ualp"
said:

Hey,

As I mentioned in an earlier post I'm in the market for a new carbon
fork. I'm focusing mostly on forks with aluminum steerers but I'm also
interested in forks with Ti steerers.

The more I learn about titanium and its use in the bicycle industry,
the less flawless of a material it seems to be. Weight limits on Ti
pedal spindles, flexy feel, arguably not a good material to use with
certain fastners, etc. It's still a compelling material to study
however, and I'm interested in knowing if it makes for a good steer
tube material (i.e., does it tend to have tight torque specs. for the
clamp bolts, what's it longevity like, does it have its own unique
dangers when cutting the tube to length, etc.).

Of course it's not a "wonder" material. However, it is a very good
material. You won't get the best results when you try and replace a
steel part with a Ti part, and you fix the dimensions (e.g. pedal
spindles), because the part pretty much *must* be weaker than steel.

Similarly, try and find an Al pedal axle. You'll NEVER find one. Does
that mean it's a bad material for frames? No, it just means you must
design to the strengths of the material.

You will find Al bottom bracket spindles, now, but *only* because they
drastically changed the part (they about doubled the diameter of the
spindle). This is good engineering -- designing around the strengths
of the material (it's light, but relatively "weak") by changing
dimensions to fit for it.

All and all if I'm concerned about strength, reliability, and safety
the most am I better off with an aluminum steerer or ti. Thanks,

It totally depends. With a 1" steerer, I'd go with Ti, because it's
stronger. These days most bikes have 1 1/8" steerers. Given equal
wall thickness, the Ti one will be stiffer, but you'll likely find it
will have thinner walls to get similar strength. Ti will still have
better fatique resistance, in the long term.