700c front wheel 2-cross lacing vs 3-cross & lateral flex

I have 2 almost identical front wheels, both: MA40,32 hole 15/16
butted spokes, D-A 8spd hubs, 700*25 Conti U2K tires. The
difference is in the spoke lacing: one is 2-cross, the other
is 3-cross. The 3-cross seems to have noticeably more lateral
rigidity than the 2-cross under similar ride conditions. This
is most appparent when riding in a moderate headwind or crosswind.
The 2-cross is more easily buffeted from side to side and I'm
constantly correcting steering. I get a similar response during
high-speed descents on less than smooth pavement. The 2-cross
wheel seems to jump around more.

Is this to be expected and common knowledge, and I'm just late
in picking up on it, or is it just my imagination?

BTW: same bike.

Thanks for any response?

Ken

On Tue, 27 Mar 2007 22:30:01 -0700, kwalters
wrote:

I have 2 almost identical front wheels, both: MA40,32 hole 15/16
butted spokes, D-A 8spd hubs, 700*25 Conti U2K tires. The
difference is in the spoke lacing: one is 2-cross, the other
is 3-cross. The 3-cross seems to have noticeably more lateral
rigidity than the 2-cross under similar ride conditions. This
is most appparent when riding in a moderate headwind or crosswind.
The 2-cross is more easily buffeted from side to side and I'm
constantly correcting steering. I get a similar response during
high-speed descents on less than smooth pavement. The 2-cross
wheel seems to jump around more.

Is this to be expected and common knowledge, and I'm just late
in picking up on it, or is it just my imagination?

BTW: same bike.

Thanks for any response?

Ken

Dear Ken,

For the lateral rigidity of different spoke lacings on otherwise
identical wheels with no tires, see #9 he

http://www.sheldonbrown.com/rinard/wheel/index.htm

In short, not yet tested.

But Damon Rinard's tests involved hanging a 25.78 lb weight from a
horizontal wheel.

In over a hundred wheels, deflection ranged from about 1 to 5 mm.

A rear MA40 32-spoke 3-cross 2x1.8 deflected about 2mm. (It's the
first wheel tested.)

The only 2-cross wheels were carbon-fiber 20-spokes and deflected 2 mm
front and 3 mm rear.

It is unlikely that any ordinary crosswind (much less headwind)
provides the 26 pounds of side force needed to deflect a front MA 40
rim 2~3 mm.

So I doubt that lateral rigidity is involved.

Aerodynamics might somehow explain a noticeable physical difference,
but that seems unlikely, too, particularly when a headwind brings out
the feeling that you mention.

For fun, you might weigh the two "almost identical" wheels on an
electronic scale and see how close they are.

Cheers,

Carl Fogel

kwalters wrote:

I have 2 almost identical front wheels, both: MA40,32 hole 15/16
butted spokes, D-A 8spd hubs, 700*25 Conti U2K tires. The
difference is in the spoke lacing: one is 2-cross, the other
is 3-cross. The 3-cross seems to have noticeably more lateral
rigidity than the 2-cross under similar ride conditions. This
is most appparent when riding in a moderate headwind or crosswind.
The 2-cross is more easily buffeted from side to side and I'm
constantly correcting steering. I get a similar response during
high-speed descents on less than smooth pavement. The 2-cross
wheel seems to jump around more.

Is this to be expected and common knowledge, and I'm just late
in picking up on it, or is it just my imagination?

The latter, IMHO. There should be only microscopic differences
between the two wheels in terms of "rider feedback" from any
difference in lateral rigidity. If anything, I'd expect the 2X to be
more laterally rigid because the shorter spokes would have a bit more
acute bracing angle (but again, since there's very little lateral
force on the front wheel when you're riding, that small difference is
going to vanish into a myriad of other bigger physical inputs).

As for the effect of the wind on the two wheels - I would expect any
difference to be VERY small, and to go the opposite way from your
perception. Normally the amount a wheel is affected by a cross-wind
has to do with how much of a surface it presents to that wind. The
only difference would be that the 3X wheel has longer spokes, so I
would expect it to be influenced (very, very slightly....) more.

I'd suggest doing a true blind test - have someone swap them out (or
not) and go for a short ride (without looking down at the wheel, of
course - they're similar enough that it should be fairly easy to not
cheat). ;-) I'll bet you a dollar to a donut that you won't be able
to tell which one you're riding.

Remember - a placebo can be an effective drug!

Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $795 ti frame

kwalters Wrote:
I have 2 almost identical front wheels, both: MA40,32 hole 15/16
butted spokes, D-A 8spd hubs, 700*25 Conti U2K tires. The
difference is in the spoke lacing: one is 2-cross, the other
is 3-cross. The 3-cross seems to have noticeably more lateral
rigidity than the 2-cross under similar ride conditions. This
is most appparent when riding in a moderate headwind or crosswind.
The 2-cross is more easily buffeted from side to side and I'm
constantly correcting steering. I get a similar response during
high-speed descents on less than smooth pavement. The 2-cross
wheel seems to jump around more.

Is this to be expected and common knowledge, and I'm just late
in picking up on it, or is it just my imagination?

BTW: same bike.

Thanks for any response?

Ken
Bracing angle of spokes on 2X is higher than 3X so I would expect the
2X wheel to be more laterally stiff..... all other things being equal.
Did you check the play in the hub(s)?


--
daveornee

daveornee wrote:
kwalters Wrote:
I have 2 almost identical front wheels, both: MA40,32 hole 15/16
butted spokes, D-A 8spd hubs, 700*25 Conti U2K tires. The
difference is in the spoke lacing: one is 2-cross, the other
is 3-cross. The 3-cross seems to have noticeably more lateral
rigidity than the 2-cross under similar ride conditions. This
is most appparent when riding in a moderate headwind or crosswind.
The 2-cross is more easily buffeted from side to side and I'm
constantly correcting steering. I get a similar response during
high-speed descents on less than smooth pavement. The 2-cross
wheel seems to jump around more.

Is this to be expected and common knowledge, and I'm just late
in picking up on it, or is it just my imagination?

BTW: same bike.

Thanks for any response?

Ken
Bracing angle of spokes on 2X is higher than 3X so I would expect the
2X wheel to be more laterally stiff..... all other things being equal.

and the slightly shorter spokes are less elastic.

Did you check the play in the hub(s)?

indeed.

jim beam wrote:

daveornee wrote:
kwalters Wrote:
I have 2 almost identical front wheels, both: MA40,32 hole 15/16
butted spokes, D-A 8spd hubs, 700*25 Conti U2K tires. The
difference is in the spoke lacing: one is 2-cross, the other
is 3-cross. The 3-cross seems to have noticeably more lateral
rigidity than the 2-cross under similar ride conditions. This
is most appparent when riding in a moderate headwind or crosswind.
The 2-cross is more easily buffeted from side to side and I'm
constantly correcting steering. I get a similar response during
high-speed descents on less than smooth pavement. The 2-cross
wheel seems to jump around more.

Bracing angle of spokes on 2X is higher than 3X so I would expect the
2X wheel to be more laterally stiff..... all other things being equal.

and the slightly shorter spokes are less elastic.

Jim, you just lambasted another poster for being a "non-techie" so I
thought it'd be a great idea to let you strut your stuff here and show
us your own technical contributions...

Just how MUCH more "elastic" are those longer spokes going to be, and
how does that actually impact the ride impressions that the OP is
asking about. Percentagewise, just how much will those longer, more
elastic spokes change the rim deflection?

Inquiring minds wanna know...

Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $795 ti frame

Mark Hickey wrote:
jim beam wrote:

daveornee wrote:
kwalters Wrote:
I have 2 almost identical front wheels, both: MA40,32 hole 15/16
butted spokes, D-A 8spd hubs, 700*25 Conti U2K tires. The
difference is in the spoke lacing: one is 2-cross, the other
is 3-cross. The 3-cross seems to have noticeably more lateral
rigidity than the 2-cross under similar ride conditions. This
is most appparent when riding in a moderate headwind or crosswind.
The 2-cross is more easily buffeted from side to side and I'm
constantly correcting steering. I get a similar response during
high-speed descents on less than smooth pavement. The 2-cross
wheel seems to jump around more.

Bracing angle of spokes on 2X is higher than 3X so I would expect the
2X wheel to be more laterally stiff..... all other things being equal.
and the slightly shorter spokes are less elastic.

Jim, you just lambasted another poster for being a "non-techie" so I
thought it'd be a great idea to let you strut your stuff here and show
us your own technical contributions...

Just how MUCH more "elastic" are those longer spokes going to be, and
how does that actually impact the ride impressions that the OP is
asking about. Percentagewise, just how much will those longer, more
elastic spokes change the rim deflection?

percentage? simple length ratio. it's trivial, but it exists. about
the same order as the angle change described by dave.


Inquiring minds wanna know...

sure you do.

jim beam writes:

Mark Hickey wrote:
jim beam wrote:

daveornee wrote:
kwalters Wrote:
I have 2 almost identical front wheels, both: MA40,32 hole 15/16
butted spokes, D-A 8spd hubs, 700*25 Conti U2K tires. The
difference is in the spoke lacing: one is 2-cross, the other
is 3-cross. The 3-cross seems to have noticeably more lateral
rigidity than the 2-cross under similar ride conditions. This
is most appparent when riding in a moderate headwind or crosswind.
The 2-cross is more easily buffeted from side to side and I'm
constantly correcting steering. I get a similar response during
high-speed descents on less than smooth pavement. The 2-cross
wheel seems to jump around more.

Bracing angle of spokes on 2X is higher than 3X so I would expect the
2X wheel to be more laterally stiff..... all other things being equal.
and the slightly shorter spokes are less elastic.

Jim, you just lambasted another poster for being a "non-techie" so I
thought it'd be a great idea to let you strut your stuff here and show
us your own technical contributions...

Just how MUCH more "elastic" are those longer spokes going to be, and
how does that actually impact the ride impressions that the OP is
asking about. Percentagewise, just how much will those longer, more
elastic spokes change the rim deflection?

percentage? simple length ratio. it's trivial, but it exists. about
the same order as the angle change described by dave.

Separating these effects makes no sense. Lateral stiffnes due to the
spokes, for a given rim and hub, is inversely proportional to the
length of the spokes. For a typical wheel, the percent change from a
radial to an n-cross spoke pattern is about 2.5% for n=2, 5% for n=3.
So if you're wheel is moving about laterally 5mm with a 3X pattern,
going to a radial pattern might reduce this by 0.25mm (about 3 sheets
of paper). Less when you account for rim stiffness.

--
Joe Riel

Joe Riel wrote:
jim beam writes:

Mark Hickey wrote:
jim beam wrote:

daveornee wrote:
kwalters Wrote:
I have 2 almost identical front wheels, both: MA40,32 hole 15/16
butted spokes, D-A 8spd hubs, 700*25 Conti U2K tires. The
difference is in the spoke lacing: one is 2-cross, the other
is 3-cross. The 3-cross seems to have noticeably more lateral
rigidity than the 2-cross under similar ride conditions. This
is most appparent when riding in a moderate headwind or crosswind.
The 2-cross is more easily buffeted from side to side and I'm
constantly correcting steering. I get a similar response during
high-speed descents on less than smooth pavement. The 2-cross
wheel seems to jump around more.
Bracing angle of spokes on 2X is higher than 3X so I would expect the
2X wheel to be more laterally stiff..... all other things being equal.
and the slightly shorter spokes are less elastic.
Jim, you just lambasted another poster for being a "non-techie" so I
thought it'd be a great idea to let you strut your stuff here and show
us your own technical contributions...

Just how MUCH more "elastic" are those longer spokes going to be, and
how does that actually impact the ride impressions that the OP is
asking about. Percentagewise, just how much will those longer, more
elastic spokes change the rim deflection?
percentage? simple length ratio. it's trivial, but it exists. about
the same order as the angle change described by dave.

Separating these effects makes no sense. Lateral stiffnes due to the
spokes, for a given rim and hub, is inversely proportional to the
length of the spokes. For a typical wheel, the percent change from a
radial to an n-cross spoke pattern is about 2.5% for n=2, 5% for n=3.
So if you're wheel is moving about laterally 5mm with a 3X pattern,
going to a radial pattern might reduce this by 0.25mm (about 3 sheets
of paper). Less when you account for rim stiffness.

let's assume rim stiffness is a constant. lateral stiffness is
therefore a function of the bracing angle and the spoke stiffness. the
greater the angle, the stiffer. the shorter the spoke, the stiffer.
you're correct that they're inter-related [lacing will affect bracing
angle /and/ length] but they are separate elements.

On 2007-03-31, jim beam wrote:
Joe Riel wrote:
[...]
Separating these effects makes no sense. Lateral stiffnes due to the
spokes, for a given rim and hub, is inversely proportional to the
length of the spokes. For a typical wheel, the percent change from a
radial to an n-cross spoke pattern is about 2.5% for n=2, 5% for n=3.
So if you're wheel is moving about laterally 5mm with a 3X pattern,
going to a radial pattern might reduce this by 0.25mm (about 3 sheets
of paper). Less when you account for rim stiffness.

let's assume rim stiffness is a constant. lateral stiffness is
therefore a function of the bracing angle and the spoke stiffness. the
greater the angle, the stiffer. the shorter the spoke, the stiffer.
you're correct that they're inter-related [lacing will affect bracing
angle /and/ length] but they are separate elements.

I saw a wheel on an MTB the other day with mostly normal 3X wheels
except the outbound spokes on the disk side of the front wheel were
interleaved twice, which put quite a bend in them at the second
crossing. I wonder what the point of that was.