Brands of Steel, BB Sway and Tall Frames?

I have a question about 1980 vintage steel frames -- 1980s Trek frames
in particular. Actually,I have 2 questions.

Here are the short (direct) versions of the questions, followed by more
detail.

Q1: I want to choose a frame that minimizes lateral deflection (a.k.a.
bottom bracket sway). My understanding is that for frames of similar
geometry and size and with similar tube diameters, this is primarily
a function of the tube's thicknesses. AS such, can the tube sets
be grouped as follows? More importantly, does this grouping
relate to noticable differences in BB sway in large frame sizes?


STIFFEST
--------
Columbus SP : Down Tube/Top Tube (1.0/0.7/1.0), Stays (1.0)
Tange #3 : Down Tube/Top Tube (1.0/0.7/1.0), Stays (1.0)
Tange Mangaloy : Down Tube/Top Tube (1.0/0.7/1.0), Stays (1.0 & 0.9)

MIDDLE STIFFNESS
----------------
Ishawata 022 : Down Tube/Top Tube (0.9/0.6/0.9), Stays (0.8)
Ishawata Mangy X : Down Tube/Top Tube (0.9/0.6/0.9), Stays (0.8)
Reynolds 501 : Down Tube/Top Tube (0.9/0.6/0.9), Stays (0.9)
Tange #2 : Down Tube/Top Tube (0.9/0.6/0.9), Stays (0.8)


LEAST STIFF
-----------
Reynolds 531ST : Down Tube (1.0/0.7/1.0), Top Tube (0.8/0.5/0.8) , Stays
(0.8 & 0.9)
Reynolds 531C : Down Tube (0.9/0.6/0:9), Top Tube (0.8/0.5/0.8) , Stays
(0.8 & 0.5)


Q2: What is the effect on lateral stiffness when the stays are made out
of High Tensile steel? I know it will weigh more but how will it likely
affect stiffness?


Here is some more background and details.....

I am 6'2" and weigh 180 lbs. I generally ride 62 - 64 cm frames.

I rode a 25.5" 1983 Trek 600 for about 10 years, including a self supported
trip across the US. The frame had 531C main tubes and non-specified
Maganese alloy stays. Bottom braket sway was a very noticable problem
for me including crank rub in the FD, ghost shifting in the RD and
occasionally speed shimy when the bags were loaded unevenly.

I have recently acquired a 1983 Trek 311, which has Ishawata Mangy X
main tubes and high tensile stays. There is some BB sway but not as
much as I remember. But, it is has been 10 years since I've riden
steel and I'm not riding the 311 nearly as hard as I rode the old 600
with 531c main tubes.

I'm wondering if I should be targeting a (more rare and earlier)
Columbus SP Trek. My understanding is that they used SP in the tall
frame sizes. But, I wonder if this will make a noticable difference.

Thanks for the help.
Dave

pinnah wrote:
I have a question about 1980 vintage steel frames -- 1980s Trek frames
in particular. Actually,I have 2 questions.

Q1: I want to choose a frame that minimizes lateral deflection (a.k.a.
bottom bracket sway). My understanding is that for frames of similar
geometry and size and with similar tube diameters, this is primarily
a function of the tube's thicknesses.

Q2: What is the effect on lateral stiffness when the stays are made out
of High Tensile steel? I know it will weigh more but how will it likely
affect stiffness?

You're barking up the wrong tree. It's the design of the frames, not
the material. You could literally build an extremely stiff frame out of
bamboo.

"pinnah" wrote in message
...
I have a question about 1980 vintage steel frames -- 1980s Trek frames
in particular. Actually,I have 2 questions.

Here are the short (direct) versions of the questions, followed by more
detail.

Q1: I want to choose a frame that minimizes lateral deflection (a.k.a.
bottom bracket sway). My understanding is that for frames of similar
geometry and size and with similar tube diameters, this is primarily
a function of the tube's thicknesses. AS such, can the tube sets
be grouped as follows? More importantly, does this grouping
relate to noticable differences in BB sway in large frame sizes?


STIFFEST
--------
Columbus SP : Down Tube/Top Tube (1.0/0.7/1.0), Stays (1.0)
Tange #3 : Down Tube/Top Tube (1.0/0.7/1.0), Stays (1.0)
Tange Mangaloy : Down Tube/Top Tube (1.0/0.7/1.0), Stays (1.0 & 0.9)

MIDDLE STIFFNESS
----------------
Ishawata 022 : Down Tube/Top Tube (0.9/0.6/0.9), Stays (0.8)
Ishawata Mangy X : Down Tube/Top Tube (0.9/0.6/0.9), Stays (0.8)
Reynolds 501 : Down Tube/Top Tube (0.9/0.6/0.9), Stays (0.9)
Tange #2 : Down Tube/Top Tube (0.9/0.6/0.9), Stays (0.8)


LEAST STIFF
-----------
Reynolds 531ST : Down Tube (1.0/0.7/1.0), Top Tube (0.8/0.5/0.8) , Stays
(0.8 & 0.9)
Reynolds 531C : Down Tube (0.9/0.6/0:9), Top Tube (0.8/0.5/0.8) , Stays
(0.8 & 0.5)


Q2: What is the effect on lateral stiffness when the stays are made out
of High Tensile steel? I know it will weigh more but how will it likely
affect stiffness?


Here is some more background and details.....

I am 6'2" and weigh 180 lbs. I generally ride 62 - 64 cm frames.

I rode a 25.5" 1983 Trek 600 for about 10 years, including a self
supported
trip across the US. The frame had 531C main tubes and non-specified
Maganese alloy stays. Bottom braket sway was a very noticable problem
for me including crank rub in the FD, ghost shifting in the RD and
occasionally speed shimy when the bags were loaded unevenly.

I have recently acquired a 1983 Trek 311, which has Ishawata Mangy X
main tubes and high tensile stays. There is some BB sway but not as
much as I remember. But, it is has been 10 years since I've riden
steel and I'm not riding the 311 nearly as hard as I rode the old 600
with 531c main tubes.

I'm wondering if I should be targeting a (more rare and earlier)
Columbus SP Trek. My understanding is that they used SP in the tall
frame sizes. But, I wonder if this will make a noticable difference.

I think you're overthinking this. I have a Cannondale touring frame in a
68cm size, that BB doesn't move. I just bought a Fuji True Temper AVR (.9
..6 .9) touring frame (2001 NOS) in a 68cm size for $70, that BB is almost
as stiff as the Cannondale. I have a 68cm Fuji touring frame from the 80's
(lugged), it's fairly stiff, not sure of the tubing. I weigh 230. I have
never loaded these bikes with more than a rack & trunk, but have never had
a shimmy or ghost shift. I had a 70's Raleigh GP that would do that, it
eventually cracked the head tube at the lug. I think modern frames are
better and cheap.

Lot o' stuff snipped about various tube sets.

Lateral stiffness has a lot to do with the bottom bracket shell and the
quality of brazing. Cast shells are better and a good brazing job as
well. Also heavier chain stays have some effect.
But shells and brazing have the most effect. I have a frame with a
..9/.6 DT, mid weight stays and a cast bracket that's as laterally stiff
as frames with heavy stays and a 1.0/.7 DT.
Really, unless you're a track sprinter it isn't a big deal. the only
place you'll notice is if the FD rubs a chainring.
Phil Brown

pinnah wrote:
I have a question about 1980 vintage steel frames -- 1980s Trek
frames
in particular. Actually,I have 2 questions.

Q1: I want to choose a frame that minimizes lateral deflection
(a.k.a.
bottom bracket sway). My understanding is that for frames of similar
geometry and size and with similar tube diameters, this is primarily
a function of the tube's thicknesses. AS such, can the tube sets
be grouped as follows? More importantly, does this grouping
relate to noticable differences in BB sway in large frame sizes?

Tube stiffness is essentially proportional to the wall thickness of the
tube in question, when the diameter is fixed.

However, stiffness is proportional to the cube of the diameter when
wall thickness is fixed. Therefore, if you want stiffness, a lugged
steel frame with "traditional" diameters-- 25.4mm TT, 28.6mm DT & ST--
is exactly what you _don't_ want.

You should seek out a frame with the largest diameter tubes you can
find, all other factors equal. Among frames with the same diameters
and overall measurements, those that are heavier will be stiffer, in
approximate proportion to their weight.

It seems likely to me that the thickness of a tube's butted end has a
greater overall effect on stiffness than that of its thinner center,
since stresses (and therefore strains) tend to concentrate in the ends
of the tube. That said, the difference in stiffness between two
commercially available tubes of identical length, diameter, and weight,
which differ only in their butt thicknesses or lengths, can't possibly
be noticeable or significant.

Q2: What is the effect on lateral stiffness when the stays are made
out
of High Tensile steel? I know it will weigh more but how will it
likely
affect stiffness?

High tensile steel has the same Young's modulus (intrinsic stiffness)
as alloy steel. If the stays you are comparing have the same outer
dimensions, then the heavier ones will be stiffer. Note that tapered
stays with constant wall thickness have better stiffness/weight and
strength/weight ratios than stays whose walls thicken as their diameter
decreases.

Chalo Colina

Phil Brown writes:

Lot o' stuff snipped about various tube sets.

Lateral stiffness has a lot to do with the bottom bracket shell and
the quality of brazing. Cast shells are better and a good brazing
job as well. Also heavier chain stays have some effect.

Neither of these effects have anything to do with frame flex,
laterally or vertically. If the brazing is poor then the joint will
fail in time. The BB shell is rigid by the BB cups that reside in it.
If it flexes significantly enough to affect frame rigidity then the BB
cups will come loose... which they don't.

But shells and brazing have the most effect. I have a frame with a
.9/.6 DT, mid weight stays and a cast bracket that's as laterally
stiff as frames with heavy stays and a 1.0/.7 DT.

Please show ho you know that brazing and BB shells have anything to do
with frame rigidity. As I said, if these joints flex enough to affect
performance then they must move significantly. How much elongation do
you believe can arise in a partially unfilled sweat braze joint that
is less than 0.001" wide?

Really, unless you're a track sprinter it isn't a big deal. The
only place you'll notice is if the FD rubs a chainring.

....and that comes out of good or poor brazing?

chalo colina wrote:
pinnah wrote:

I have a question about 1980 vintage steel frames -- 1980s Trek

frames

in particular. Actually,I have 2 questions.

Q1: I want to choose a frame that minimizes lateral deflection

(a.k.a.

bottom bracket sway). My understanding is that for frames of similar
geometry and size and with similar tube diameters, this is primarily
a function of the tube's thicknesses. AS such, can the tube sets
be grouped as follows? More importantly, does this grouping
relate to noticable differences in BB sway in large frame sizes?


Tube stiffness is essentially proportional to the wall thickness of the
tube in question, when the diameter is fixed.

However, stiffness is proportional to the cube of the diameter when
wall thickness is fixed. Therefore, if you want stiffness, a lugged
steel frame with "traditional" diameters-- 25.4mm TT, 28.6mm DT & ST--
is exactly what you _don't_ want.

You should seek out a frame with the largest diameter tubes you can
find, all other factors equal. Among frames with the same diameters
and overall measurements, those that are heavier will be stiffer, in
approximate proportion to their weight.

It seems likely to me that the thickness of a tube's butted end has a
greater overall effect on stiffness than that of its thinner center,
since stresses (and therefore strains) tend to concentrate in the ends
of the tube. That said, the difference in stiffness between two
commercially available tubes of identical length, diameter, and weight,
which differ only in their butt thicknesses or lengths, can't possibly
be noticeable or significant.


Q2: What is the effect on lateral stiffness when the stays are made

out

of High Tensile steel? I know it will weigh more but how will it

likely

affect stiffness?


High tensile steel has the same Young's modulus (intrinsic stiffness)
as alloy steel. If the stays you are comparing have the same outer
dimensions, then the heavier ones will be stiffer. Note that tapered
stays with constant wall thickness have better stiffness/weight and
strength/weight ratios than stays whose walls thicken as their diameter
decreases.

Chalo Colina

nice summary.

On 2005-04-27, pinnah wrote:

I have a question about 1980 vintage steel frames -- 1980s Trek frames
in particular. Actually,I have 2 questions.

Here are the short (direct) versions of the questions, followed by more
detail.

Q1: I want to choose a frame that minimizes lateral deflection (a.k.a.
bottom bracket sway). My understanding is that for frames of similar
geometry and size and with similar tube diameters, this is primarily
a function of the tube's thicknesses. AS such, can the tube sets
be grouped as follows? More importantly, does this grouping
relate to noticable differences in BB sway in large frame sizes?

A larger frame creates a longer lever-arm and thus creates more "sway." To
compensate for this, stiffer -- that is, thicker or larger diameter --
tubing can be used. Standard frame components in those days were made to
accommodate standard tubing diameters, which meant unless you were willing
to go to the expense of have specially sized components made, the outside
diameter of the tubing had to remain standard. Thus, the only way to
increase stiffness was to increase wall thickness. Changes in
manufacturing processes in the 80s eventually made this less of a burden,
though.

Q2: What is the effect on lateral stiffness when the stays are made out
of High Tensile steel? I know it will weigh more but how will it likely
affect stiffness?

The material (High-Tensile vs Mang alloy) will not make a difference in
stiffness. Regardless of alloy used, a thicker or larger diameter steel
tube will be stiffer than a thinner or smaller diameter tube.

I rode a 25.5" 1983 Trek 600 for about 10 years, including a self supported
trip across the US. The frame had 531C main tubes and non-specified
Maganese alloy stays. Bottom braket sway was a very noticable problem
for me including crank rub in the FD, ghost shifting in the RD and
occasionally speed shimy when the bags were loaded unevenly.

A large frame in addition to a touring load will accentuate this problem.

I'm wondering if I should be targeting a (more rare and earlier)
Columbus SP Trek. My understanding is that they used SP in the tall
frame sizes. But, I wonder if this will make a noticable difference.

Yes, but it is because the SP tubing is thicker, not that the alloy makes
it stiffer. The reason for using alloy steel in bicycle frames is not
that it increases the stiffness (it doesn't) but that it increases the
tensile strength of the material. This means that you can use a thinner
and lighter tube without sacrificing strength -- which is not the same
thing as stiffness.

--

John )

On 2005-04-28, philcycles wrote:

Really, unless you're a track sprinter it isn't a big deal.

Or if you're a tall rider on a large frame carrying a touring load, which
is what the OP said he was doing when he experienced the "sway."

--

John )

On 2005-04-28, chalo colina wrote:

Tube stiffness is essentially proportional to the wall thickness of the
tube in question, when the diameter is fixed.

However, stiffness is proportional to the cube of the diameter when
wall thickness is fixed. Therefore, if you want stiffness, a lugged
steel frame with "traditional" diameters-- 25.4mm TT, 28.6mm DT & ST--
is exactly what you _don't_ want.

You should seek out a frame with the largest diameter tubes you can
find, all other factors equal.

Assuming, of course, that stiffness is the overriding feature you want
out of the frame. But is that reasonable to assume? I can't help but
remember all those mountain stages won using flexy Vitus aluminum frames.

--

John )