[smoothspinner]

There is a curious reversal of lacing pattern on two of Mavic's current wheels. Mavic's web site provides the following spoke patterns on the rear wheels of two current wheelsets:

• Ksyrium Elite: Isopulse="spokes that are radially mounted on the freewheel side and are crossed by two on the opposite side"
• R-SYS: "rear radial non-drive side, crossed 2 drive side"

That is, the lacing pattern is reversed between the two wheels. On the Elite, the radial is on the drive side, with the cross-2 on the non-drive side, while on the R-SYS, the radial is on the non-drive side, with the cross-2 on the drive side.

What different characteristics would be expected from these two wheels due to the reversal of the lacing? Is there an obvious reason that Mavic has chosen this lacing reversal? Is there, somewhere, an explanation of the relative advantages of radial vs. crossed lacing?

Thank you.
smoothspinner

 

[bopApocalypse]

Is there an obvious reason that Mavic has chosen this lacing reversal? Is there, somewhere, an explanation of the relative advantages of radial vs. crossed lacing?

Obvious: SELL MOAR WHEELS.

For rear wheels, the issue is that radial spokes don't transmit torque very well. To demonstrate, take a pen, and hold it with your left hand - your hand is the rim, the pen is the spoke. Try pushing or pulling, with your right hand, perpendicular to the pen - this is a radial spoke. Now try pushing or pulling at a 45/135 degree angle to the pen - this is a crossed spoke.

Basically, with one design only the driveside spokes are transmitting all the torque from the hub, in the other design, the non-driveside spokes are transmitting all the torque, but depend on the stiffness of the hub shell to do so.

 

[smoothspinner]

Thank you for the response.

If I follow your argument correctly, the wheel with the cross-2 lacing on the drive side should be more efficient, since it does not depend on the stiffness of the hub shell to transmit the torque to the spokes on the non-drive side.

Yet, Mavic says of their Isopulse lacing:

_Increased stiffness due to a better tension balance between each side of the wheel
_Greater efficiency due to better transmission of power (my emphasis)

I can only guess: Is it that the reduction of torque through the hub shell provides an equal net torque on either side of the wheel, since the spokes on the non-drive side are more efficient in transmitting the torque? And if so, if this is a better design, why would they reverse it on the R-SYS?

Is it meaningless marketing, or is there a good reason?

 

[rruff]

Is it meaningless marketing?

Yes.

The only good reason to use the NDS for torque transfer, is that radially lacing the DS allows you get the DS spokes over a wee bit farther... or more than a wee bit on Mavics aluminum spoked wheels. That is where it started. The downside to this is that the NDS tension is low, and when you ask those spokes to take radial and lateral loads *and* torque loads, those spokes are more likely to go slack.

On the R-Sys this is a non-issue since the NDS spokes operate in tension and compression both.

 

[Kerry Irons]

Wheel efficiency

If I follow your argument correctly, the wheel with the cross-2 lacing on the drive side should be more efficient, since it does not depend on the stiffness of the hub shell to transmit the torque to the spokes on the non-drive side.

In order for a wheel to be less efficient, there would have to be significant flexing (and associated energy loss). Assuming reasonably stiff hubs, the difference in efficiency is virtually zero.

Is it meaningless marketing

Yes.

 

[wankski]

that was the usual lacing for Mavic Ks...

this changed with the R-sys since they could not cross the very wide carbon spokes... the DS is actually alu spokes, crossed, and only the NDS is their 'soooper, dooper' carbon BS.

That said, the R-Sys tested way stiffer than the Ks....nto saying much tho... not the stiffest alu wheelset, way overpriced, and about as aero as an elephant, thanks in part to those rediculous spokes....

what ruff said about the lacing of the Ks is dead on... it did equalise tensions a bit more - but the NDS still would run at less tension than DS, which is not good for transmission... Ks are crappy wheels, and it was no wonder they tested poorly in lateral stiffness despite having wide spokes and heavy rims.