If so I'm really curious what particular numbers you were chasing to determine what the 'better' wheel was. I have my own ideas on this which is why I'm interested.
Its benefits reside chiefly in the process and I argue better process leads to better wheels. Wheel quality depends on knowledge, time allowed, and concern. By capturing and presenting wheel information this way, you can get the most from your knowledge and skill. By working faster, you can do a better job in the same amount of time.
So there are some objective qualities that you could judge wheels by. Consistency is key, and knowing where the limits of the materials used are and how far away from those you are. An under-tensioned wheel is safer than an overtensioned one, the undertensioned wheel will fail gracefully, the overtensioned one will desintegrate.
If you are optimizing for speed of building that's another matter altogether, I was hoping for a clear and objective difference in quality of build.
Well...an undertensioned wheel is a recipe for broken spokes. Why not correctly tension a wheel? The correct tension is quite a lot higher than most builders go. An overtensioned wheel is not very easy to produce, at high tensions truing the wheel becomes super-critical in that tiny changes move the rim absurd amounts, and that is the point to back off.
I have heard of top level downhillers using minimal spoke tension for better compliance and traction. They also have professional mechanics and piles of wheels to use for a race weekend. Meaning their wheels have to be just reliable enough to hold together for a 4 minute race run.
But they do lose tension over time, so it doesn't hurt to periodically check. That's also a good way to spot cracks in rims, which and do happen especially on bikes that are built once and then used for years.
Paul Aston (World Cup pack fill, former Pinkbike journalist) also made note of experimenting with extremely low tension and implied it worked pretty well: https://www.downtimepodcast.com/paul-aston-2021/
Really though, where you have the resources to experiment with something like spoke tension, you are likely to end up with a couple outliers.
Overtensioning is actually pretty easy, and I've seen more than one wheel respoked by novices that were overtensioned to the point that they were simply dangerous (because when one spoke goes the wheel will immediately respond and if you're unlucky it could even break).
Not quite, but it is engineering.
> Overtensioning is actually pretty easy
Again what materials are you using? When at optimal tensions in a mtb wheel from mavic, you would already be turning really hard and in danger of damaging the nipples before overtensioning. It really is not that easy if you tensioned the wheel evenly
Engineers will use math to get to their solutions, and will then back off from that 'perfect' solution to give them a safety margin to take into account excursions into borderline overload, material defects and so on all balanced against costs.
That does not add up to me.
You can go by tone to a pretty high degree of consistency.
Still, I trust my ability to read a tension meter more than my ability to match pitch. Props to anyone who feels otherwise - pitch pipes are much cheaper than good tension meters.
e.g. https://apps.apple.com/gb/app/spoke-tension-gauge/id51887082...
There are three failure modes that I've seen for an over-tensioned wheel:
1) The wheel will buckle in a potato chip shape - This is generally something that will happen at build time, and can be recovered from. 2) The inner wall of the rim will pull away from the side wall. This was particularly bad with the old Mavic MA single eyelet rims, but I've seen it on at least one other rim as well, a lightweight MTB rim laced as a tandem rear. (Completely inappropriate choice of components) 3) Spokes can be improperly tightened without lubrication in the threads, causing windup which later (when unloaded under tire pressure and rolling loads) causes the pinging sound of the wheel going out of true. This is not a structural failure, but it does cause the wheel to require attention.
For the buckling limit case, the ultimate load depends on the torsional stiffness of the rim, and a few other minor factors. Box or closed section rims are much better, U shaped rims are bad. Paradoxically, thinner spokes are better, and you need to lubricate the nipple threads and the contact with the rim. I used to really like the Mavic Open4 rims with the double eyelets, but that's gone out of style now.
Yes, I've seen a couple of those, typically mail order or equivalent bikes sold without a mechanic involved in the sales process. Guess who gets to fix them :)
> They're a lot easier to build, because spoke windup and nipple galling don't start to be an issue until you get to decent tensions.
Lubrication during build is the key I think.
> The wheel will buckle in a potato chip shape - This is generally something that will happen at build time, and can be recovered from.
Interesting, I've never seen this at build time but I've seen people that build their own wheels crash terribly because of this, so far only (fortunately) rear wheels. Just thinking about having that happen to a front wheel while on the move is enough to give me views of dentist offices.
> The inner wall of the rim will pull away from the side wall. This was particularly bad with the old Mavic MA single eyelet rims, but I've seen it on at least one other rim as well, a lightweight MTB rim laced as a tandem rear. (Completely inappropriate choice of components)
This I've never seen.
> Spokes can be improperly tightened without lubrication in the threads, causing windup which later (when unloaded under tire pressure and rolling loads) causes the pinging sound of the wheel going out of true. This is not a structural failure, but it does cause the wheel to require attention.
This is the main thing I've come across frequency wise. I suspect some manufacturers don't particularly care about what they ship as long as the customer pays and it makes it out of warranty.
> For the buckling limit case, the ultimate load depends on the torsional stiffness of the rim, and a few other minor factors. Box or closed section rims are much better, U shaped rims are bad.
Yes, logical too. Box or closed section rims can be ridiculously stiff.
> Paradoxically, thinner spokes are better, and you need to lubricate the nipple threads and the contact with the rim.
Can you explain the 'thinner spokes are better' bit? I use thicker spokes on the gear side if a cassette is very high so the wheel is almost flat on one side to get symmetrical tension, but otherwise equal on both sides and thicker for heavier loaded bikes (such as tandems). Would love to understand this bit.
> You need to lubricate the nipple threads and the contact with the rim
Yes, this is key. You won't be able to get the spokes properly tensioned if you don't do that (or you end up eating up the hole around the spoke nipple). That's a great way to ruin a rim or to end up with busted spoke nipples.
Oh, and also important: use the proper key! (not those round ones but the ones that go over and on, obviously sized exactly for the nipples you use).
The rim deflects inward as it contacts the ground. This is controlled by the stiffness of the rim. The deflection untensions the spoke. The cycle of tension/untension as the wheel rotates causes fatigue and also if the tension reduces to near zero allows the nipples to unwind. A thinner spoke elongates more for a given tension, so the rim deflection reduces tension proportionally less.
For example, given a thin spoke that elongates 5mm under tension, and a thick spoke that elongates 2mm, a 2mm rim deflection reduces tension 40% on the thin spoke and 100% on the thick spoke. So the thick spoke will fatigue and fail faster.
Ideally use the thinnest spokes that can deliver the desired wheel tension. This is not commonly done in cheap wheels because thin spokes have more windup and more spokes interact when truing so the build takes more time and care.
The key is that spokes never fail from tensile overload (barring something like a branch going through the wheel), they fail from fatigue cracks. A spoke will be unbuildable before it has too little tensile strength.
The MA had 2cm long cracks in a similar location, maybe gapped 1mm or so, at most of the drive side spokes.
Another thing I've seen is rims with the spoke nipples pulling so hard that the rim material was flowing upwards, so you got all these little bulges (they definitely weren't designed like that, not all of the spokes had them).