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Campagnolo advertises the Khamsin Asymmetric Wheel:

Screen shot of Khamsin Wheel

What is an asymmetric wheel and (given that we expect wheels to be symmetrical), why would one want an asymmetrical one? How is it related to dish?

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    asymmetrical rear rim profile allows for better balancing of spoke tensions between drive and non-drive side, giving better symmetry to an asymmetric component. Increased efficiency and reactivity are sure to be noted I've read this theory or variations thereof before, kinda hard to tell if it's merely a theory without much (any?) research to back it up – stijn Dec 28 '16 at 19:17
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    There is related subject: "Why offset the rear rim to the hub and not the hub in the frame?" bicycles.stackexchange.com/questions/8998/… – False Identity Dec 28 '16 at 19:41
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    I notice that these wheels are quite inexpensive as Campagnolo wheels go. They have been building and selling asymmetric wheels for years, and are now offering them at these basement prices. Make me think there's sometime new about to be released :-) – andy256 Dec 29 '16 at 12:31
  • New for 2017: Campagnolo Symmetric wheels - adds addition reactivity and balance to the light and dark sides of cycling. – RoboKaren Dec 29 '16 at 20:27
  • @andy256 they have discontinued all hubs except Record. If you want to be in road wheel business, you need to either sell cheap wheels or restrict yourself to high end. Symmetric rim isn't any more expensive to produce than asymmetric, but may save some costs in wheelbuilding and warranty. – ojs Dec 29 '16 at 21:16
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The "asymmetric wheel" terminology is a little misleading. This particular wheel has an asymmetric rim.

Any bike with a rear derailer setup will have an asymmetric rear wheel, because the gears take up space.

The usual way to handle this is that the spokes on the gear side have less of an angle (closer to vertical) than on the non-gear side. (That is, they have different dish angles) Since an angled spoke also pulls outward slightly and the horizontal forces need to balance, the gear side spokes also have higher tension.

That more vertical angle and higher tension makes the gear side weaker. Combined with pedaling force tending to apply more on the gear side, the most common spoke failure is on the gear side of the rear wheel.

In other words: the gear side of the rear wheel is the limiting factor in the strength/lightness balance when engineering and building a rear wheel.

When a rear rim is asymmetric, what that usually means is that they've moved the line that the spokes all connect into away from the gears. This allows the angle to be slightly further from vertical while forcing the non-gear side a bit closer to vertical. That is, both sides will have closer to the same spoke angle. That means that the tension on both sides can be closer to matching.

Having the dish angle and tension closer to matching allows for the hub and spokes to be stronger and/or lighter. (but may require strengthening the rim slightly)

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    Note that it is possible to have the frame be asymmetrical (offset), but there's tradeoffs with that and seems to mostly only be a thing on fatbikes. – freiheit Dec 28 '16 at 22:20
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    I find the high end asymmetric wheels to be amazingly strong laterally. And they are very light. One can only assume that these benefits have trickled down. – andy256 Dec 29 '16 at 12:34
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    @freiheit It was more a thing on early fat bikes when they were trying to get chainline correct (not rubbing on the tire) with limited options available for hubs and BB options. With newer 170 and larger spacing regularly available from many hub manufacturers, such work around designs are no longer necessary. – Deleted User Dec 29 '16 at 21:08
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The wheel itself is not asymmetric, but the rim is. The reason for this is that the cassette hub itself is asymmetric, and shifting the spoke attachment at rim allows more even spoke tension.

The clear benefit of even tension is durability. On one hand, peak tension and associated stresses are reduced, on the other hand loose spokes cause problems and increased minimum tension reduces those. Efficiency and reactivity are marketing speak, but surely appeal to buyers.

Dish is another term for asymmetric spoke angle and tension. The asymmetric rim allows less dish for same hub and rim dimensions.

6

Both answers are correct but I want to add a bit more. The asymmetric in the title also refers to the spoke lacing of the wheel. If you look at the photo, you'll notice that it is cross-spoked on the drive side but radially spoked on the non-drive side.

This feature can also be seen below in combination with asymmetric spoke construction. Both the lacing and spoke construction are asymmetric (steel on the drive side and carbon on the non-drive side):

A Mavic Ksyrium SLR wheel with asymmetric spokes

So the question is, what is it good for? Probably not much. In theory a radially laced wheel can be built with shorter spokes (and thus be made lighter) but the benefits in this respect are marginal. As an owner of a Khamsin wheelset, I can confirm that it also makes the process of truing the wheel more complex.

Additionally with a dished rear wheel, the spoke tension on the drive side is much higher than on the non-drive side (and presumably the nature of the load is quite different as well) so it makes sense that using dissimilar materials might give some kind of weight or stiffness benefit but the benefits are likely to be very small.

In conclusion then, it's probably just another way for bike companies to sell expensive gear to people who prefer shopping to training.

  • Never saw such a cash cow, +1 for info and pic – TheBlastOne Dec 29 '16 at 14:10
  • Asymmetric spoke patterns have been around for decades and sold under many names. The old non-"asymmetric" Khamsin had asymmetric spokes, too. The one in picture was called R-sys and it was an engineering and PR disaster. Regarding "probably not much", other answer explain why the asymmetric rim and spoke pattern are useful. – ojs Dec 29 '16 at 16:59
  • Why are they harder to true? – Criggie Dec 29 '16 at 20:13
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    The nipples on the G3 rims aren't distributed equally around the rim (they're in bunches of 3) and that, coupled with getting the dishing and tension right makes fixing wobbles more time consuming than with a regular spoke pattern. There might be a knack to it but I'm yet to come across it! – HJCee Dec 29 '16 at 20:27

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