This post deserves a TL:DR summary, which is: If you aren't super comfortable with road tubeless and willing to spend some time and expense figuring out exactly which combo works for you, and also willing to petentially suffer a reduction in the lifespan of your wheels, stick to tubes. With a whole bunch of data now showing superior rolling resistance with clinchers and latex tubes, that may be the best way to go in any case. The ability to use latex tubes is another bonus of aluminum rims.
For mountain bikes, tubeless is mandatory. For cross, it has its challenges (which we've done a heck of a lot to help eliminate) but the benefits can be so profound that the juice is for sure worth the squeeze. For road, though Mike and I personally use tubeless, we haven't been evangelical. It comes with downsides, which we'll talk about here.
We've been observing and talking about spoke tension drop in clinchers for a couple of years now. Since I've done THE WORST job at tagging posts, it's hard to find all the posts on the topic, but these two posts from last spring are good examples. There were a bunch of forum discussions in the spring of 2014, but I can't even recall which forum they were on. We even made a video to show the effect last spring.
Wheel Fanatyk has what might be the second best wheel blog out there, and they did a series of posts in the fall about this whole topic, including the outward splaying of brake tracks which we'd discussed in above-linked post called "Pressure Drop Follow Up." What they did in particular, for which I have huge appreciation, is measure a bunch of tires to find how tightly they will fit. Their whole methodology and execution of this is excellent. What their measurements reveal is something that anyone who's installed more than one kind of tire will already have known - tire bead circumference varies by manufacturer and model.
They've also measured overall circumference of a number of different rims, but they haven't shown the more relevant tire trough and bead seat diameters (which are simple secondary measurements from what they've done and shown). The overall circumference is of little value in its own right as, for example, a Zipp 404 shows a large outer diameter, but 404s are known to be relatively easy to fit tires onto (perhaps too easy?).
In order to resist the higher inflation pressures of road tires, road tubeless tires need a tight fitting carbon bead. The carbon bead more or less doesn't stretch, which is critical to having the tire not blow off the rim, and thus to keeping your teeth in your head. In that respect, it works quite well, but at what cost?
Non-tubeless road tires have either wire or Kevlar beads (if you're reading this, you probably have Kevlar beads). You probably notice that your tires get easier to install over time, which is because the beads stretch a bit over time. This stretch reduces the constricting pressure that the tire imparts on the wheel.
Compressive tire loads cause a reduction in the circumference of the rim. Wheel Fanatyk estimates a possible 1mm reduction in the circumference, and my calculation gave me an estimate of .1mm in diameter reduction, so they estimate a bigger effect but we're not that far off in the absolute. I based mine off of "the spoke tension drop is x, the thread pitch of a nipple is y, the spoke tension drop is equal to z turns of the nipple, therefore the diameter reduction must be..." The important thing is that we're both seeing the same effect, in the same direction, with reasonably similar magnitudes.
Compression is bad for the wheel for several reasons. It takes more initial spoke tension to maintain the minimum necessary functional spoke tension. Compression changes the dish of a wheel. Compression puts stress on the rim that almost certainly shortens a rim's useful life span.
At the risk of speaking against my book somewhat here, I have two road bikes in current use (one disc, one rim brake, otherwise more or less identical) and those four tires are all tubeless. It works fine for me, but on a scale of 1 to 10 in tubeless experience, I'm about a 643. So if you are willing to invest time and money into getting your road tubeless set up perfectly, knowing that it comes with the potential to compromise your wheels, then it may be worth it to you. Otherwise, tubes are your best bet.
Dave – you're good!! That is all…
zak, you're assuming that large tension drops seen in modern rims are a result of companies designing their rims to also be tubeless compatible. This may play a part, but maybe the majority culprit for the tension drops are companies that cater too much to the weight-weenie crowd when they under design their rims material wise?
i'm with you on the tubeless road set up Dave.. I'm not a fan. The tubeless rims in use are a massive compromise some of which can cause tension to drop as much 25% ( a certain US made low profile carbon rim drops so much it can affect the dish as much as 2mm ). there is the risk of burping tires and to be honest the range of tires and development is seriously lacking.. if you want the sweet ride of a pair of hand made tubular tires then run tubs… if its too much of a compromise some open tubulars and some thin tubes and you most of the way there..for MTB or commuting sure thing.. but for performance road setups there are to many compromises to be made
Glad you enjoy my humor and reading our blog, Zak. (Zak is the owner of Skunkworks Bike in Sydney, Australia). Notice also that among any issues that tubeless tires for road might have, they don't burp because of high pressure. That's, as you say "straight up nonsense."