Intentionality; the New Astral Cycling Backbone: By John Jones

Websters Dictionary describes intentionality as "The quality of mental states (e.g., thoughts, beliefs, desires, hopes) that consists in their being directed toward some object or state of affairs. It's usually used in reference to a person, but I don't think it's only individuals that display a sense of intent; companies -- in this case rim manufacturers -- also convey intentionality, for better or for worse.

When I work on a wheel built elsewhere I usually get a good idea of the companies intentions. I've seen 32 hole mountain bike wheels built with a 2 cross lacing to save weight, held together by inferior 2000 series alloy nipples, once again to save on the scales. I've seen rims from well-regarded companies that are so flimsy they suffer significant loss of spoke tension once the tires are mounted. I can only assume that these companies' sales are driven by favorable reviews and stated weights in magazines (in which they just happen to advertise). Cynical, I know, but I have to expect that the totality of their intention is to sell a lot of product, even at the expense of making a good product.

Astral Cycling comes with a different approach. Readers of my blog will know that I have a high regard for this Eugene, Oregon based sister company to Rolf Prima, manufacturers  of paired-spoke wheel sets. The two companies are housed under the same roof, and share many of the same rim profiles and correlating design philosophies. Paired-spoke wheels like the Rolf demand a robust spoke bed to prevent pull through; having left and right spokes attached to the rim less than an inch from each other would play havoc with insubstantial rims. Here's the good stuff; Rolf Prima and Astral use the exactly same rim extrusions. They have the same super strong spoke bed, just with a different drilling arrangement. This gives Astral rims an extra margin of durability over the majority of conventionally drilled rims on the market.

I recently built a pair of Astral's new 27.5 Backbone alloy rims. The 30mm internal width is perfect for modern tires widths up to 2.8 inches. It's an asymmetrical rim which means the spoke bed is pushed 2.5mm to one side, resulting in close to even spoke tension between left and right-side spokes. Similar spoke bracing angles for driveside and non-driveside spokes results in wheels that steer and brake better. The rims are made from 6069 aluminum alloy rather than the more common 6061. The tensile strength of 6069 is substantially higher than 6061 and as a result, the rim can be made light without sacrificing strength.
   

So, how did they build up?

I wish all rims felt this good during the tensioning procedure. They went from loose to tight to perfectly tensioned in an orderly, progressive manner. As with all wheel builds, it was the usual juggling act of balancing trueness (both lateral and radial), tension and dish; but the rims never required that I double back to put out a fire. Built with 64 robust Wheelsmith double butted 14 gauge spokes and brass nipples, total weight came in at 1812 grams.

So, now back to intentionality. If I had to discern what the Backbone is all about just by working with it, I would put it this way; Astral has aimed to make a rim that's light, but not too light, that benefits from modern designs such as asymmetric profiles and wisely employed a superior alloy that can take the knocks and hard use in its future. Rather than frills or gimmicks, they intend for the rim to succeed on good ol' word of mouth. That's how it feels to this wheel builder.

Thanks. I'll take it.

 -John Jones