This is a subject that came up in the spoke pitch thread.

Are there any good reasons (other than tradition) to physically cross & bend spokes? Particularly if we're dealing with thin aero spokes on a deep carbon rim, which is extremely stiff laterally to begin with?

Yes there are.

First, I think the word interlaced is what you're after, rather than crossing.
Crossing usually refers to the whole radial/tangential thing, 2X, 3X etc. Interlaced (IMO) is the phrase used to describe the over-under-over pattern that a spoke usually takes on a cross-laced wheel.

For wheels carrying torque through the hub there are good reasons to do, and there are good reasons not to.

Keep in mind that for a cross laced torque carrying wheel, half the spokes will lose tension and the other half will gain tension as torque is applied to the hub.
In an interlaced wheel, the spokes gaining tension will strain against the spokes losing tension, reducing the amount of tension that they lose.
In a non-interlaced wheel this doesn't happen, so the loss of tension for half the spokes is bigger.

Now, I admit that I haven't measured how much of a difference this makes in numbers.
Some wheels for some riders obviously have enough margin so that it isn't an issue. But for others it may well be the tiny difference between early spoke failure and decent life for the wheel.

On the flip side, a non-interlaced wheel will be torsionally stiffer.
With the spoke running straight as an arrow from hub to rim there's less initial flex or wind-up as the force is transferred from the hub to the rim.

The theory is sound, but whether I'd be able to tell the difference in a blind test I don't know. I certainly wouldn't bet on it.

I've tinkered around with it a bit, built some experimental wheels that way. Mine have been ride-wise indistinguishable from traditionally laced wheels.
There's been some buzzing on high-speed descents, and it's harder to get spoke reflectors to stay in place.
The buzzing may come from some other feature of the wheels as well, I haven't enough comparison data to say.

Already answered in your other thread...

...so why a new thread?

=8-)

+1,

First of all, when something is done consistently by pros for a century, there's usually a good reason.

The transfer of tension Dabac describes is the main benefit of over/under lacing. But it goes beyond simple torque transfer in a rear wheel.

When looking at wheels, the thing to consider isn't tension increase, but tension reduction, and the change in length involved. When the rim deflects inward there's only a certain amount possible before the spoke goes slack. This varies with the amount of elongation that the tension originally created, but for a 2mm spoke it's very little, even at 100kgf. (thinner spokes elongate more at the same tension).

So what interlacing does is allow the tighter neighboring spoke to load the spoke sideways taking up some of the reduction in length, so it takes more deflection to slacken the spoke.