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.
JLP -We've never billed carbon as either great or bad. That's a mischaracterization that you're choosing to use. I bet you don't remember or know about how much caution we preached through the first generation of carbon, do you? While everyone else was saying "this is our mold, we engineered it, we're the best, we're so rad!" our story was "they're a good product for a specific purpose, and a product that has serious limitations (which we disclose), and these are open mold rims from a supplier we've verified but they are not our mold." Then we developed the Rail, with the same supplier, using a shape that we developed. We tested it against a Zipp 404 before we green lighted production. Despite being better than the 404 at the shallow angles of attack that are now broadly agreed to prevail, we used a then-widely accepted angle of attack distribution that showed the 52 as being slightly slower than the 404. Even though a strong case could have been made for the opposite. In that whole exercise, we were both the first brand to test against a relevant standard wheel, and the first not to bend things to our benefit. If anything, we bent them away from our benefit. Then we came out with the Rail 34 through popular demand. THE ENTIRE TIME WE WERE SELLING CARBON, more often than not, people who came to us looking for carbon were sold, by us, on the greater value and utility of aluminum rimmed wheels. There are legions of people who will verify this. Even though great strides were made in brake heat management and resistance, carbon wheels to this day continue to be reliant on extremely tight production controls, and are vulnerable to a multitude of problems having nothing to do with braking. But why take my word for it, take this guy's https://www.youtube.com/watch?v=ET1jRVynOBA I'd plan to spend about 2 hours watching Raoul's videos. Following a wind tunnel trip in August of 2014, we found out that competent alloy rims were starting to approach aerodynamic par with shallower "climbing" carbon clinchers, at little to no weight penalty, and with tremendous benefits in terms of cost and braking. While most brands would choose to remain blind to the facts we were seeing, and would sure as hell prefer that their customers did too, we aggressively pursued AND FREELY SHARED all the information we found. And we very naturally came to the conclusion that shallow carbons were a wheel without a use case that we could endorse, and we cut them from our lineup. It was the most honest move that we possibly could have made. Even the gap between even the 52 and its peers to alloys isn't one that provides a meaningful benefit to the majority of our customers. Following that, as we were then down to selling only one carbon rim, our volume in carbon declined. This causes a bunch of issues in your supply chain management, and also makes the amount you are spending on various expenses to just be in the carbon came – insurance hugely prominent among them. And that makes you seriously question whether it's a game you want to be in. As we've explained many many many other times, with price pressure coming from closeouts and serious discounts happening every day thanks to the global supply market's over saturation, and with price pressure also coming from below thanks to unbranded carbon (and yes, a lot of that is crap, and I will plainly say so – we've tested a bunch of it), there was no case we could make to ourselves to continue with carbon. At least certainly not our own with the cash flow implications, insurance costs, quality control headaches, constant night-time Skype calls with Taiwan, etc etc. Our story on carbon now is the same as it what I described in the very beginning, as has been through our entire history – that it's a product that has benefit in certain use cases, but has substantial liabilities of which anyone considering it should be aware.As to tubeless, if you can find an instance where we (or I) could credibly be said to have been evangelical about road tubeless, it would shock me. For cross, I absolutely believe in it and endorse it as my take on the best solution for most citizen cross racers, for reasons which I've elucidated on end. BUT, we've also gone to the trouble of testing it beyond what anyone else I've ever seen has done, to be able to give you reliable combinations that we very confidently feel will work great. And for mountain biking, my thoughts are clear. Back to road tubeless, point me to where I've made the judgment that it's bad. Please. Because I haven't. I've merely pointed out some factors that haven't necessarily been popularly considered before. If you know of a more ethical path, or one that has our customer's interests more at heart, for us to choose, please do tell. I'm just dying to hear it. And if the message you've taken from this is that I'm saying "tubeless aluminum is no good," then you haven't read very closely. I'm sorry that you need to see things in such black and white, and can't discern my point from all of this information. And it's a sad sort of funny when we, having displayed a level of honesty, transparency, responsibility, and customer-centrism matched by exceptionally few companies ever (Patagonia and Clif come to mind), get tarred with the brush whatever it is you're accusing us of.My recommendation is to calm down, watch the Leuscher videos, re-read as much of this and all of the rest of our blogs as you must, and see what you get out of it. If you find something with which you take exception, or which contradicts what I've said here, please feel free to bring it up. I can promise I won't spend this amount of time addressing it again, but I'm not shutting the door to discussion. We never do.
Dave,What is your point? In the beginning, you sold carbon wheels. You said how great they were. Then all of a sudden, you stopped selling them, and said how bad they are. The you started selling aluminum tubeless wheels and told us how great they are. And now, are you saying tubeless aluminum is no good?
Hans – Thanks. There are a couple of potential downsides to building with higher spoke tension. It stresses everything – hub shell, hub flange, rim. It's not hard to find hubs that spec spoke tension limits. Chris King at 120kgf is one I know top of mind. Tune is less than that, but those are lightweight almost specialty hubs. You expose the flanges to a higher risk of cracking, and you can in more extreme cases ovalize the bearing bores. Rims are simply more prone to cracking with higher spoke tension – when was the last time you saw a front or non-drive spoke pull through a rim? It's always the highly loaded drive side that goes. Excluding eBay/Alibaba carbon rims that claim 300kgf max spoke tension for a second, you don't see many (any?) rims that have more than about a 130kgf limit. The other extreme is that a rim with too much spoke tension can taco. When it's that highly loaded, unbalance the load or stress the wheel just a little bit and WHOMP – wheel looks like a Pringles chip.I've stopped thinking about spoke tension primarily as "how much tension can I put on the drive side" and shifted to thinking about "how much tension do I need on the non-drive side." Of course disc fronts are reverse but you get the point. It's a semantic difference but it counts. And it's pretty easy to get 65kgf on the non-disc side of a symmetrical disc front wheel with 105kgf or so on the disc side. This one's top of mind because yesterday's last wheel was a 28h SL25/CLD front, and that's how we build those. Even with a 25% drop in spoke tension, that's enough to keep the offside from going slack. The 11 speed, 130mm spaced rear road wheel represents probably as much as you can compromise a wheel structure and hope to have it work reliably with an acceptable margin for error. At 125kgf drive side, you're barely over 60 on the non-drive, so you more or less need all of that drive side tension. But much more than that is asking for trouble. It's a relatively fine line.Road front wheels, on the other hand, are stable and great structures. They simply don't need much more than 90 to do everything they'll ever need to do. They're also often radially laced, which is the most demanding lacing from the flange's perspective, so you don't want to crank those spokes way up and you really really don't need to. You could lace rim brake fronts at 70 and they'd almost certainly work great, but it would freak people out. It sounds like you're generally using similar tensions to us, which is not surprising because that's sort of where we are with wheels in the world right now.
You guys write good stuff; this type of article would always bring out both sides of the camp. I will admit happily that tubeless is not without alternatives for road tires; I used to run GP4000S with latex and those are nice tires. But the tubeless setup with Pro Ones worked with my rims (a set of CBK carbon rims and some boat anchor Flo30 rims for commuting) and the ride feels as nice to me and resistance to flats has been phenomenal. So I am very happy.More to the point on the science, though, you bring up a good point about the beads not stretching and tension drops. Is there any downside to building with higher tensions to achieve the correct tension once it drops? E.g. build to 135kgf to yield 120kgf after tires installed? I also am not really sure I understand the logic in using substantially lower tensions for front wheels, in particular disc. Just risk of spokes pulling through over time? Dependa on rims, but I typically target a finished tension of ~110kgf for front now, though only because I feel there must be some disadvantage to matching a rear (e.g.) 120kgf.
this is a pretty amusing line Dave….'Wheel Fanatyk has what might be the second best wheel blog out there'while your blog is very prolific, it is often padded out with circle talking and straight up nonsense, unlike the Wheel Fanatyk blog which could be considered the single best resource for 'modern' wheel building. Understandably your are trying to sell things to people and your blog helps that in a big way but its a a bold and inaccurate statement