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It seems conventional wisdom says to alternate inward vs outward spoke heads going around the flange when lacing a wheel, like this:

Alternating Lacing

However, I'm wondering what the reason for this is, and if it has advantages or disadvantages for the flange, lateral stiffness, and/or lacing the crosses. It does look nice to have them all match, like this:

Constant Lacing

Is this 'bad'? Can it only be done in radial spoking? Could you have more lateral stiffness from all outside spokes, and/or less lateral stiffness from all inside spokes (because of more/less angle spread of the spoke angles)? The ideal answer would explain the pros and cons of:

  • Alternating Inward/Outward Lacing (Standard?)
  • All Outward (heads facing inward) Lacing
  • All Inward (heads facing outward) Lacing
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Try it and see. I suspect you'll discover why a laced hub alternates. –  Daniel R Hicks Apr 19 '12 at 21:56
    
I suspect you mean it's difficult in the crossings, which does not apply to radial spoking, and less for fewer crossings, perhaps not at all for 1x, and then more and more as you get to 2x, 3x, and 4x... but my suspicions are not good answers, nor did I order the right lengths for radial, 1x or 2x crossings. –  Ehryk Apr 19 '12 at 22:14
    
Look at your first figure. Imagine the spokes all on the same side. –  Daniel R Hicks Apr 19 '12 at 22:14
    
So in 3x, the spokes run into each other too near the flange. This doesn't answer the question for radial, 1x, or 2x. –  Ehryk Apr 19 '12 at 22:29
    
Or for really large flanges, or rims/hubs with low spoke count like 24 or lower. –  Ehryk Apr 19 '12 at 22:36
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3 Answers

up vote 2 down vote accepted

The answer to "why alternate crossing spokes" is pretty much settled by the subtle suggestions from DanielHRicks and the direct and correct conclusions from the OP, in the very comments below the question.

The two remaining questions would be:

  • When is it possible to use non-alternating configurations, besides radial spokes?
  • In case of non-alternating configuration, should the spoke enter the flange holes inwards or outwards.

(I am, on purpose, not including the already much discussed pros and cons of using crossing vs radial.)

The first question is: there is also the SPIRAL configuration, shown in the picture below taken from the front wheel of my fixie:

enter image description here

(note the missing spoke at 2 o'clock...)

This spiral configuration is achieved when the spokes you have are too long for a radial lacing. Then you twist enough that they can fit. This is not so good, because it creates torsion in the hub's body, but I've seen that (and ridden that) a lot, and nothing terrible happened so far. Of course, it could not be safely used with disk brakes.

Now the good part: should the spoke run inwards (like the photo you posted and the photo I posted) or outwards? My answer would be: OUTWARDS, ALWAYS! I know that is pretty to see all those tiny spoke heads neatly arranged one beside the other in a pearl-collar-like pattern, BUT:

  • Outwards running spokes give a wider leverage to resist lateral forces. That means the same lateral force on the rim would cause a smaller variation in spoke tension.
  • It is a bit easier to insert spokes that run outwards (although in radial lacing it is not so important).
  • Most importantly: spokes running outwards touch the flange as they run to the rim, just above the elbow. That means the elbow is isolated from most of the flexion they would suffer whith the successive loading and unloading caused by wheel roll. This decreases fatigue significantly, hugely increasing the lifetime of the wheel.

So, the answer is your second option: All Outward (heads facing inward) Radial Lacing, UNLESS (!!!):

  • You use a hub for which the manufacturer forbids the use of radial lacing (most of them). Radial lacing might theoretically cause too much stress on the hub flange, since the force is applied in a direction where there is the least amount of material to resist the pull.
  • You use disk brakes (from previous answers, I think you're going to use those multi-mechano-power U-Brakes, so no problem).

(just for the record, the wheel in the photo I posted is opposite to what I am advising. That is because I already bought it that way. And I think the missing spoke - broke yesterday - has to do with this lame inward-running pattern.)

Hope this helps!

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Interesting Pattern! Could it be possible that lacing pattern has some advantages (all the drive side ones are pulling forward, the ones where a disk would be stopping are pulling in the braking direction), when combined with all outward would add lateral strength (and looking great)? –  Ehryk Apr 20 '12 at 3:56
    
Also, 1x (and possibly 2x) with certain spoke counts may be possible to not-alternate. I'd really like a concrete "this is when you can, this is when you can't" answer. –  Ehryk Apr 20 '12 at 3:57
    
This lacing pattern has the only real advantage (besides the show factor) that you can use spokes with lengths you perhaps could not use with other lacings. If you use it with disk brakes, or in a rear hub, when you apply torque to the hub, one side would have the tension increasing, and the other would have it decreasing. That would cause the rim to move sideways, dangerously. That said, it is NOT possible, at least safely. Besides that, I believe the braking and acceleration forces transmit equally to both sides, not mostly to the side where the disk or cassette seats. –  heltonbiker Apr 20 '12 at 4:40
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It looks like some builders call this the 'Race Lace,' and by pre-bending the spokes near the elbows will allow crossed patterns to be laced in this way.

http://spokeanwheel.110mb.com/lacingcl.htm#rl details this method and even shows 5x done on a 36 hole rim/hub:

36h 5x Race Lace

Not only do the leading/trailing spokes lay nicely next to each other, it appears to have the following properties:

  • Advantage: More lateral stiffness due to wider effective hub width
  • Advantage: Even lateral pull from all spokes, not alternating
  • Advantage: Perfect 90 degree angle from hub flange (not due to inward heads)
  • Disadvantage: Increased weight
  • Disadvantage: Increased fatigue at first crossing
  • Disadvantage: Harder to lace (especially for machines)

This isn't really meant to be a convincing argument to 'Race Lace' everything, but it certainly moves the prognosis from 'because you can't' to well within the realm of possible. If anyone has further reasoning why this is undesirable, I'd like to hear them.

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Radial lacing is the only sure safe pattern for what you are suggesting.

1x might work, but the spokes would not lay nicely, and would defeat the purpose stated of having a nice looking lacing.

2x or 3x would damage the spokes at the first crossing, regardless of spoke count or flange size. It would also look stupid, and be dangerously weak, because since the spoke could not lay smoothly without damaging the underlying spoke, the wheel tension would be difficult at best to make even.

When you cross the spokes, they cross under each other creating a "weave" which adds bracing to the structure. If that happens too close to the flange that brace becomes a tension pint, which at minimum will make extra odd noises and I expect (because I haven't tried it) would cause spokes to saw against each other. If you could stand the long enough, you'd see broken spokes.

Saying "Conventional wisdom says" implies that there is some unknown reason for this pattern, and that perhaps its just tradition or aesthetics. In this case, conventional wisdom is only pointing out the obvious: 2 objects can't occupy the same space at the same time without conflict.

I hope that helps.

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Spokes bend easily, would they really be damaged or weakened significantly if you bend one out over another in the 2x or 3x case? Or they just wouldn't be pulling straight up at the flange? 'Conventional Wisdom' was a poor choice of terms in retrospect, but I didn't know the answer when I asked the question. –  Ehryk Apr 20 '12 at 4:16
    
When you cross the spokes, they cross under each other creating a "weave" which adds bracing to the structure. If that happens too close to the flange that brace becomes a tension pint, which at minimum will make extra odd noises and I expect (because I haven't tried it) would cause spokes to saw against each other. If you could stand the long enough, you'd see broken spokes. –  zenbike Apr 20 '12 at 6:20
    
I added that point the answer. I realized I was unconsciously assuming that the answer was obvious, and that the question was designed to stir people up, as often happens when convention is questioned without (apparent) good cause. I apologize if I offended you. That wasn't intentional, and I'll try to avoid similar assumptions in future. –  zenbike Apr 20 '12 at 6:25
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I only have 2 extra in one length, and after spending $100 on Wheelsmith DB14 spokes, I'd prefer to keep them nice. However, I stayed up all last night coding, bought a domain name at 3am, and lauched www.wheelspoking.com where I plan to play with all sorts of 'theoretical' builds, and later start computing spoke length for them and the 'pretty' builds, like the spirals and grouped rims/hubs, then make it a bit more interactive. –  Ehryk Apr 20 '12 at 22:10
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It will also allow me to visualize where the crossings will happen for a given lacing/hole count/etc., so I can see when 1x and/or 2x become possible to outward lace. I'm much more interested in the possible than the useful. –  Ehryk Apr 20 '12 at 22:13
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