Originally Posted by
p2templin
I just don't understand the "logic" of comparing wheels by weight. It's not the raw weight that creates the strength, it's the engineering of the wheel. The Chukker is a wide wheel, so it's going to have more weight than a narrow wheel. However, that width exposes the wheel to more stresses, so you'd expect more weight to maintain comparable strength with a narrow wheel, and would need even more weight to be stronger than the narrow wheel.
Regardless, I don't know why I'm typing this. You're already the self-proclaimed expert wheels, and it makes no sense that you're asking the rest of us for input. Why not ask Velocity?
The Velocity Dyad and the Mavic A719 are both heat treated and share a very similar shape in their extrusion. Comparisons are fair, considering the significant difference is extrusion thickness (that is rim weight). The Velocity Chukker is essentially the Velocity Dyad (both are 24mm wide) with almost the height of the Deep V. The Velocity Dyad is 24mm wide and 22mm tall, while the Chukker is the same 24mm footprint but 32mm tall. This translates into a much much much stiffer rim.
Regarding your point of asking Velocity, I have. Velocity is standing behind their rims. Even though in this case it is clear that the build was at least half the problem, Velocity is standing behind their product. They offered to rebuild us a Dyad using proper 14g straight spokes for our outlier application. In all fairness Velocity truly believes that a properly rebuilt Dyad stands a good chance of holding up and being a really great lightweight wheel for us. They did however, give us the option of also going with a Velocity Chukker or even the Velocity Psycho. We were going to go with the Psycho, but it just might be too wide (for our frame). Stay tuned, I may change my mind and go with the Psycho rebuild instead of the Chukker. Will be shipping out next week (have to decide by then).
Also, as I said before most of the tandem enthusiasts I know aren't in world class shape, as strangely most are in the autumn of their lives and while still enjoying all that life has to offer are sporting some tummies in their jerseys. Additionally, the other younger tandemists we know have a very fit cyclist captain but a very very very not fit stoker (who isn't a cyclist by any means). So our perception of what the average tandem team looks like may be skewed, but I doubt it. I still say 350lbs is an average tandem team.
The context of all of this is that I alone am less than 350lbs (though just barely). My experience is that our rebuilt Dyad failed with ONLY ME on the bike. A normal tandem load wouldn't be so equally displaced front/rear as ours was with just me (the captain) on it when it failed the second time after only three miles. The weight bias is much much more so on the rear wheel.
I'm glad that so many others are having such great luck with their Dyad rims on their tandems. However, the Dyad is based on the extrusion of the Aerohead, actually the Aeroheat, which is itself a beefed up version of the Aerohead. They build racing wheelsets for 110lb female racers out of the Aerohead because it is so light:
http://boulder.craigslist.org/bik/2664630222.html
There is a heck of a difference between a racing wheel for an outlier lightweight rider wanting a very lightweight wheelset and something bombproof for touring, let alone tandeming or even more demanding a touring tandem.
I think the Dyad is one of the best lightweight rims out there. For a single it is an absolutely bombproof rim. As I've stated multiple times, just bought another 48h Dyad for my 27" wheeled touring bike (not even built up yet). However for "most" normal tandem teams I just don't think the Dyad is the workhorse rim they are looking for. Heck, even for loaded touring there have been some failures for people on Velocity Chukkers (not Dyads mind you). This couple touring on singles opted to have theirs replaced with the Psychos:
http://journal.goingslowly.com/2010/...y-rims-part-3/
Obviously, people will have different experiences. Plenty of people of small stature will have great success running the Dyad, as they would with many rims that are singles rated. Heck, there are teams running rims that are racing rims for singles, and have no problems. If you are a very lightweight team (that is combined you barely weigh more than a larger cyclist) you can probably run whatever you want.
My only point is that the Dyad is not deserving of its reputation as a bombproof TANDEM rim. It is a bombproof rim, just not on a tandem. Heck, the Chukker, which is considerably stronger than the Dyad, and for which Peter White says builds the strongest wheel he's ever seen (he doesn't even carry the Velocity Psycho) has failures. Which is not to say that both aren't great rims, just that application and context are key.
The technology and engineering that goes into rims isn't all that advanced. Although, in fairness the Dyad is much much stronger than anything else in its weight class (480g for a 622) due to that ratio of height to width that Velocity has perfected. However, and again, it is a very accurate measure of a rim's strength and stiffness to compare weight, and again the Dyad, Mavic A719, and Velocity Chukker line up perfectly by strength and stiffness as they do by weight. This isn't rocket science. There are rims that are unnecessarily heavy for their strength/stiffness like the Sun Ryno Lite. Which is not to say they aren't strong or stiff, but just that they aren't modern advanced rim profiles and are a little more bloated than they probably need to be. However, even for those you can't beat the price.
Also this is a friendly reminder that the original topic is about 630 (27") rims, not tandem rims in general of which almost all use 650B or 700c. Thanks!