Originally Posted by
Retro Grouch
If you lace the first spoke in the second flange in the wrong hole, the spoke pattern on each side will be correct but the pulling spokes will seem too long and the spokes going the other way too short or vice versa. When you tension the wheel your spokes will seem long, long, short, short all the way around the rim.
(Lets assume 36 hole 3x wheels for this reply.)
OK, I get it now. However...
Lets say that all the spokes on one side of a previously correctly built wheel are being replaced. The spokes get laced one hole (20 degrees) off from where they should be. The result is a 2x/4x lacing pattern as described here:
http://www.terminalvelocity.demon.co...ld/crossed.htm Calculating spoke lengths for a typical small flange front road wheel shows that 3x spokes won't work in that 2x/4x pattern. They'll be either 6mm too long or too short.
Lets say that a fresh wheel was assembled with this error. The hub can turn to equalize the error across both sides. They'll now be just 10 degrees off. The lacing pattern on both sides could be called 2.5x/3.5x. The spoke lengths will now be just 3mm long or short. OK, such a wheel might make it to a truing stand before the error is caught.
Lets assume a rear wheel (numbers are for a Tiagra DeepV). The 3x spokes are between 5 and 8mm long or short for the 2x/4x pattern. Even for 2.5x/3.5x, the spokes are 3 to 6mm long or short. The error would be caught before this wheel is fully assembled.
Hmmm. (trying something) Aha!
Assume a symmetrically laced rear wheel assembled without error. Turn the hub just 2 degrees the "wrong" way. The lacing pattern on both sides could be called 3.1x/2.9x. All the spokes end up about 1mm long or short. They'll be in a LLSSLLSSL... pattern.
Now turn this hub just 0.7 degrees the other way. This could be called 2.965x/3.035x. Now all the spokes reach almost the same spot in the nipples! The only casualty is a 2kg-force tension difference. That's small enough to be unmeasurable.
If a wheel is not symmetrically laced (ie the Shimano rear disc wheel recommendation), then turning the hub either way causes the LLSSLL... pattern to show up and get worse the more the hub is turned.
So - a LLSSLL... pattern is most likely a nipple tightening error, not a lacing error.