While I have a bit of explaining to do below, let me not bury the lede: The tires you want to race on do not currently work on the wheels you may want to race on. This is especially the case in aero road wheels, but it is and will become an issue for aero tri and TT wheels. This is solvable, but you should understand the landscape before you make purchase and use decisions.

I took a lickin’ from some of you (if you’re on our Reader Forum) back when I declared 3 or 4 years ago that virtually all tri bikes will come with hydraulic disc brakes. I won’t post mortem that debate, just, you know this turned out. About a year and a half ago, same type thing. Our future is road tubeless was my declaration and I got a lot of well-reasoned pushback. But – just as with hydraulic disc brakes in tri bikes – this wheel standard is your future and mine regardless of whether it’s the future you want. This road tubeless future is moving quickly toward the here-and-now, because most of the long distance pro triathletes you respect are racing on tubeless already.

In the last month or so I’ve drilled down a bit further. Your road tubeless future is not clincher (clincher in cycling parlance generally assumes bead hooks), but is tubeless using a hookless bead. A hookless bead means the wheel is now made like the wheels on your car, your motorcycle and ATV, and the trucks, airplanes, tractors and heavy equipment that serve you. The inside of the rim wall is straight. (See image above.)

Bicycle wheels with hookless beads – straight wall rims – are what you will be buying, both for low and high pressure tires, skinny and fat, road and offroad. Everything. Again, you can complain about this, but like disc brakes in tri bikes, this is your future and in many cases your present. I talk to the wheel companies and I know what they’re making. There’s what they’re selling you know – some hookless rims for road tubeless, some with bead hooks – and there’s what they’re making next, which is largely hookless. Why? The wheels can be made stronger, lighter, cheaper, and more aero. Since the process to make them is less costly, in a competitive semi-commodity industry the same wheel made hookless should be less costly to you.

The thing about hookless, both the wheel and the tire (such as the ENVE tires, in aftermarket packaging above) need to be made with greater precision. The hook is there as a safety mechanism. There are performance problems with the hook, but, in a world where there are no clear standards for manufacture, the bead hook is like the “lawyer lips” on your fork ends: they are a pain, they are more time consuming to get the wheel off, but there’s a layer of safety. Same thing with the bead hook.

Enter the ETRTO, which is the European association that creates standards for every kind of pneumatic wheel, including bicycles. And I’m precise when I say “wheel.” They only make specs for wheels, and it’s up to tire companies to make tires to conform to those specs. Or not. And, “not” is the case for many or most of the tires you prefer. (As we’ll get to.) The ETRTO in 2019 came up with a set of specs for both hooked and hookless rims. The hookless rim specs were the most important, because this is the wheel everybody wants to make. ENVE was an early champion of this wheel type, and has had to endure the arduous work approving tires that conform to its wheels designs; and disqualifying others. Now that the ETRTO has created a wheel spec – which ENVE’s wheels already pretty closely conform to, in broad strokes – tire companies know what to make. But have they made these tires?

In 2020 Zipp and CADEX (just above) have also produced wheels that conform exactly or closely to the ETRTO spec, and we’ve written about them here (CADEX and the Zipp 303 series). I’m not allowed to tell you what other hookless-bead tubeless road wheels are in process, because the wheel companies making them are selling wheels right now and they don’t want you all to delay purchases. Just, it’s my strong suspicion that this is the wheel type of the future, because there is no performance spec you value that this wheel doesn’t optimize.

This brings us to the tires you’ll ride. What you want, of course, is ride quality, low rolling resistance, aerodynamics, and flat resistance. You expect the tires to mount on the rims without undo force used. You expect those tires to not blow off the rims, be subject to burping or pinch flats, and so on. These are all reasonable asks. In response wheel companies have lately chosen to make wheels – including road and tri wheels – with hookless beads. Why? Here is my rough outline of the trends that led to this.

I would say that HED (and maybe the now-defunct American Classic) is the company most deserving of credit for widening the internal bead width, and ENVE was either right behind HED, or right there alongside. This is the width of the wheel I’m talking about, the distance between the rim walls, inside-to-inside. That internal bead width for road used to be 15mm, and as we’ll see below one of your favorite tires – the Corsa Speed TLR – was built assuming a rim with a 15mm internal bead width. Then companies started widening that distance, and making wider tires to match. The old Zipp 303 Firecrest was (is) a heck of a wheel, a real breakthrough wheel. But that internal bead width was 19mm. Wheel companies then started making rims with internal bead widths in the neighborhood of 20mm and 21mm, and you could reasonably use these as gravel wheels, for tires up to and beyond 40mm in width, assuming the wheel was strong enough. The new Zipp 303 line (below) has internal bead widths of around 23mm.

The wider the rim, the lower the tire pressure. When I began racing typical race pressures were in the range of 120psi to 130psi. Now the tire is hard to the touch at 75psi, assuming you’re riding a 28mm tire on a rim with a 23mm internal bead width. This lower pressure allowed wheel companies to contemplate a hookless bead without the threat of a blowoff. When I’ve got the camper on the back of my RAM 3500, heading out for a bicycle adventure, I’ve got more pressure in the truck tires than in the tires of the skinny-tired road bicycle thrown in the back.

So, enter the hookless rim for road tires. As a nonexpert observer, lower pressures are what triggered the move to hookless beads. The ETRTO is recommending max pressures of 73psi on hookless rims. This seems crazy low, until you snap an inflated tire with your finger and get that high-pitched ping. This is the way this new generation of wheels and tires are made to be ridden. In fact, a lot of these road set ups are meant to be ridden at more like 45psi or 50psi. Here is Greg Kopecky’s most recent wisdom on and guidance for tire pressures, but even this, though only a year old, was published before the recent rush of wheels with wider bead widths, and tubeless construction.

Why go through all the hassle? Why not just continue to make the wheel with a bead hook? The wheels can be made lighter, stronger, more aero, more inexpensively, with greater precision, with the resulting system offering lower rolling resistance. Otherwise, there’s no good reason ;-)

About the “more aero” claim. What do I mean by that? The drawing above is courtesy ENVE wheels. I swiped it off their website (with their permission). Now, I think this drawing takes some liberties. This is sort of a best-to-worst-case scenario. However, look a the image below, of a CADEX tire mounted on a CADEX wheel. Back when we used to glue Conti tubulars on our wheels in the 1990s, we used liquid silicone in that gap between the brake track and the tire to smooth out that hourglass shape. You don’t see that in the image below.

Here’s the negative to hookless beads: If you push too much air into the tire, it’ll get up underneath the bead and force the tire off the rim. Because of this, wheel companies often fudged, making their wheels a little larger in diameter; and tires companies fudged the other way. This led us to a truly regrettable invention: the tire jack. Fortunately, when the ETRTO created specs for tubeless wheels, many leading wheel companies have embraced these. I’ve written about some of them recently: CADEX and Zipp. ENVE’s hookless bead rims were so early they actually predated the ETRTO’s specs, but the wheels nevertheless fairly closely adhere.

Likewise, tire companies have raced to meet the spec. The most obvious is Schwalbe, with the 2019 update of the Pro One and Pro One TT. The other obvious examples are the wheel companies themselves, that have made tires to match their new straightwall rim designs: Zipp, CADEX and ENVE. Greg just wrote about ENVE’s tires. When we inquired about the sales performance of the tires, what we got in reply to our email was, “quadrupled our original forecasts… sold what we thought would be a 1-year forecast at launch.”

And as you know I have waxed effusive about the CADEX wheel/tire system. Once you have the spec, and you control the design of both the tire and the wheel, you can make a darned near perfect system. That said, there is no reason why a tire company can’t make a tire that’s part of that darned near perfect system, since the ETRTO’s specs are published, and are very specific.

If you’ve gotten this far, there is an obvious problem. Here are your current tire preferences (poll still ongoing):

This is what Ken Avery of Vittoria wrote us about its Corsa Speed: “The Corsa Speed TLR 700x23c was developed 5 years ago following the valid standards at that time, so it was developed on a 15mm internal rim width. Since then, we adjusted the width in production slightly to be more compliant with the increasing rim width. Therefore, it will work well on the wider more modern rim width standards, but the tire will measure slightly wider when used on rims wider than 15mm internal. These tires have been designed for hooked rims. We do not currently approve these tires for use on hookless rims.” (Underlining is mine, here and in the paragraph below.)

Here is what I got from Jan-Niklas Juenger at Continental: “For our Road tires we do not want them to be used hookless, one reason being that their max pressure is above 5 bars and we must make sure all our customers are on the safe side. On the other hand: If a tire that was not designed for hookless is used on such a rim, the ETRTO gives a range of rim heights between 5.5mm (which is the average height for most TL hooked rims) and 6.5mm (which would be the safe option, but will increase mounting issues), one tire can work on one manufacturer working with the higher rim height. Unfortunately we cannot check/control all manufacturers and because 5.5mm is very much critical to blow off with our current GP5000TL, we have to rule out all hookless options for the time being. However we are working hard to make it work in the future!”

Add Conti and Vittoria, there are the brand preferences of more than 4 in 5 of you. No problem if you’re riding wheels with a bead hook. There are current, late model wheels made with bead hooks, like the Zipp 858 and 454 tubeless wheels ridden in Kona last year by Sebi, Jan and Ali Brownlee.

And… consider the final sentence in the quote from at Continental’s Jan-Niklas Juenger: “However we are working hard to make it work in the future!” So, by the time you purchase a wheel that’s made in this new design, there may be a conforming Conti tire (likewise Vittoria).

But as for now, the tires most of you want to use for racing in a tri are made for a wheel construction type that is not considered by most wheel companies the optimal way to make a wheel. The beads on these tires are often too flexible, hence the construction of the CADEX tire, which is made to a precise diameter, large enough to go on a wheel hands-only, but with a stiffer carbon + Kevlar bead, that resists stretch.

The changeover in wheel style (both released wheels and designs in the pipeline) in skinny-tired milieu is most apparent in road, which you might now call 700c road/gravel (as we haven’t been able to kill a single recent road wheel when used for hard core gravel). But it’s coming to tri, and you will now need to pay close attention to which tires you place on these new wheels.