I just read this page http://www.jpracingbike1.com/content/6-pourquoi-un-montage-de-roues-artisanales- explaining that 'artisanal' aka hand built wheels are better for many reasons, such as having better tension and static stress distribution. This would imply better feeling from the saddle as well as better durability. How much truth is in there? It makes me feel as if I should find time to rebuild my campagnolo zondas from scratch.
The parts of this topic that usually get glossed over in written sources and hearsay are:
- Not all wheel production machinery and processes are the same. It's kind of the opposite, actually. It's a spectrum. And, in at least Holland Mechanics' case, the lines have modular components. For example, before the truing robot there can be another machine that presses the spokes around the flanges in a fashion pretty similar to how handbuilders do it. Or, for time and cost reasons, there might not be. And the truing robot itself has settings that are used to dial runout and tension balance precision versus machine time. The list of variables that potentially impact quality goes on and on. The point is that there is no valid discussion of handbuilt versus machine that doesn't get any more granular than that. There are bad handbuilders and very exacting, time-intensive machine production setups.
- A lot of named wheelsets are produced with a mix of machine and hand steps. Some OEM and repair wheels are too.
A related question is whether the best fully automated setups can build the same wheel as well as the best handbuilder. In other words can they do as good on setting the spoke line, stress relief, tension balance, and runout. I don't know the answer to that and I doubt you'll find very many people who do and are also willing to answer publicly, since proprietary machine setups exist. One reason I think the answer is probably technically no is that I've never seen or heard of a machine that even tries to replicate the spoke punchy steps a good wheelbuilder does to create true maximum level pre-bedding of the spokes into the hub flange. But, that's only relevant to j-bend wheels, so it depends on what kind of wheelset you're talking about, and it's around the least important hand-buildy thing a handbuilder does, and a lot don't even do it. But, it is part of the list of things that are needed to make a wheel that's absolutely as resistant to going out of true as possible.
Taking the time or expense to hand-build-ize a prefab set that's going strong is a waste. If it's surviving in use and has zero issues with going out of true or breaking spokes, let it be. It only realistically got that way because the steps taken to produce it were good.
The Holland wheel robots I've been around all use nipple torque to gauge tension, which is hokey and from a quality and accuracy perspective is inferior to using deflection, but conversely is a way of doing it that adds only marginal complexity, i.e. it's better than nothing and if the alternative was a whole other apparatus inside the machine coming over to donk into the spoke, nothing is possibly what you'd get. I don't know whether there are any that use deflection, but I've also seen a lot of prefab sets with near-perfect tension balance, which implies either hand-finishing or that there are machines out there able to do it, which in my experience the torque-based methods can't, or can't reliably, or at least not within the realm of practicality.
The above may all come off as apologist; it's not intended to, and machine built wheels are usually perfectly bad to be sure. But at the same time, having some or all of the steps automated in and of itself does not by any means mean the wheel is inferior.
Straight pull spokes enter the conversation in an interesting way. I don't love straight pull, but eliminating the j-bend interface eliminates the need to manually set the spoke line at the hub. Using automation to reliably do that step as well as a skilled human is hard. Once you've done that, it's straightforward to see how non-time-stingey machine building with human QC and touch-up of tension level and tension balance gets you basically all the way to a handbuilt wheel. With bladed spokes to create perfect QC against windup and a bunch of threadlocker, you have a recipe for largely machine-built named prefab sets that stay very true for their service life. Many of the better sets follow this pattern.
Note also I've tried to answer the question literally, and my answer boils down to full handbuilt vs everything else is in and of itself not what determines good versus bad, reliable versus not, etc. If the question were what are the benefits of a wheel that possesses the full suite of characteristics that give a wheel maximum reliability and lifespan versus a wheel that doesn't, and what are those characteristics, that is a different discussion completely.
Wheelbuilding is a combination of art and science.
A machine-built wheel has no art - by that it lacks the "touch" of a skilled person building the wheel. The machine that builds wheels is a technological marvel of moving parts and order, and is a massive time saver. This also brings wheels down in price.
By comparison, a hand-build wheel by an expert wheel builder will be measurably more durable, and more accurate, having less runout over all. But it will take 30-300 minutes to build what the machine can do in 1~5 minutes.
As a measure, consider the trueness of a rim built into a wheel. I had a brand new cheap (and therefore machine made) wheel that went out of true within a month, and needed tweaking multiple times a year. Contrast that with some fancy expensive-when-new Mavic tubular wheels I own, which have never varied. The metric is "how long the wheel stays in true"
A compromise is for the machine-built wheel to be tweaked by a human after assembly.
The challenge for the machine is to get all spokes to an even tension on each side, such that the rim is in the right place and still round. Sounds straightforward, but every change in tension affects every other spoke somehow. With 16-36 spokes that's a lot of variables all together.
Perhaps if a wheelbuilding machine could tension every spoke at the same instant, perhaps with one torque sensor per spoke, then that continuous feedback would produce a better wheel. As it stands, a modern wheelbuilding machine cuts, threads and installs a spoke, and then fits a nipple. But only once at a time.
There are several ways in which a hand built wheel is superior:
- Stress relieving. You must grasp the spokes hard to stress relieve. A machine may not easily be able to do this.
- Lubrication on nipple-to-rim and nipple-to-spoke interfaces. A machine that installs the components may not install sufficient lubrication, making it impossible to fully tighten the nipples.
- Tension measurement. A machine may use torque to estimate tension, but this is inaccurate, as it depends on the lubrication.
- The art of balancing between equal spoke tension and highly true wheel is better with an experienced wheelbuilder. A machine may lack the judgement that which of the two competing attributes to compromise on and how much. This is more important with cheap rims that may not be so accurately built. A very high quality rim from a brand such as DT Swiss should need less compromises.
- A hand builder is more likely to properly tune the wheel long enough to get to high tension and accurate trueness. Machine built wheels often have lacking tension, because it's faster to build low-tension wheels than to build high-tension wheels. Of course a human wheelbuilder can also save time by building a low-tension wheel but the very best wheelbuilders won't accept such a task.
One feature is better with machine built wheels:
- Spoke windup. A hand built wheel requires the wheelbuilder to assess how much to over-do every adjustment and how much to back off to result in zero spoke windup. A machine can press on the rim with a hydraulic press when tensioning the nipple, thus doing the nipple turning with zero tension, and then release the pressure to restore tension. Thus, invariably the amount of spoke windup on hand built wheels varies based on the experience of the wheelbuilder. The worst wheelbuilders say that some amount of pinging can be heard with a newly built wheel. If you ever encounter such a wheelbuilder, don't walk away; instead, run away!
It is possible for a professional wheelbuilder to do the final touches to a machine-built wheel (add lubricant to each interface, a grease can't be added later but light oil will do the job; tension to an equal and high tension; stress relieve; find a correct balance between equal tension and true wheel; spend enough time to tune the wheel to get the best possible result).