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UpFromOne wrote:1. Since the hub flanges must be offset from the centerline in order to accept the cassette, the DS and NDS hub flanges experience different stresses. One goal is to equalize these flange stresses as much as possible.
2. Another goal is to equalize the spoke tension on each side, to better keep the wheel true.
3. Another goal is to equalize the stresses at the rim holes. (The pulling force from each side of the hub)
1. A smaller (lower) hub flange experiences less stress than a high flange.
2. A longer spoke requires more tension than a shorter spoke to do the job (resist external forces on the wheel).
The assumption in a crossed DS + radial NDS is that the torque force starting from the cassette will reach the DS flange more so than the NDS flange. I don't agree. Modern hubs have enough material between the flanges, and are strong enough to almost completely resist torque equally at each flange.
It appears that the radial NDS pattern is trying (among other things) to reduce the NDS spoke length. After all, a radial spoke is shorter than a 2x spoke. Combined with a 2x DS, this seems to be an attempt to equalize the spoke lengths used on each side, with the implied objective of equalizing spoke tension because of more equal spoke lengths.
The problem is that this only addresses spoke tension, without dealing with hub flange tension, or tension at the rim. A radial spoke, being shorter, will require less tension. Therefore, it aggravates the inherent difference in tension between the DS & NDS due to the uncurable offset. This is further aggravated by the flange design, which is typically lower on the NDS. Again, I have to assume that this parameter is an attempt to cure the spoke angles. The narrower DS angle will be relieved with a higher flange, thus angling the DS spoke out just a hair more.
So these modern hubs designed only for NDS radial spokes (especially the straight-pull spokes with an even lower effective flange diameter) are missing the overall effect. If I had to have radial on one side, I'd actually rather have it on the NDS (like ZIPP) than the DS.
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