Tubeless rims without side hooks (Hookless) – how dangerous are they really?

Two incidents in the professional peloton have sparked much debate about the safety of rimless rims. onboard hooks The UCI is looking into this issue, but what does this all mean for us end users? We decided to shed some light on the background and asked the industry's enlightened minds the key question on all of us: toe or not?

Two incidents in the professional peloton have sparked much debate about the safety of beadless rims. The UCI is looking into this issue, but what does this all mean for us end users?

It looked terrible. The insert had torn, there was sealant everywhere, and the tire had come off the rim. Here's the scene when Thomas De Gendt's rider pinned himself against the road barrier on stage 5 of the UAE Tour. Just last year, the European Tire and Rim Technical Organization (ETRTO) made changes to recommendations for tire and rim size compatibility with tubeless systems, which received little attention. It was only the dramatic images that circulated across the Internet after this live-streamed accident that truly sparked a debate about the safety of beadless rims. But the big question is: what are the advantages and disadvantages of beadless rims for end users who don't have team escort cars and personal mechanics? And are they safe to use?

Best offer, theoretically

Let's start from the beginning. In theory, rim manufacturers for frameless tires promise the following: “We can save up to 20% of production costs by simplifying the production process, which reduces the number of work steps, material requirements and reduces waste. In turn, you use only tubeless tires and get improved aerodynamics, cornering grip, shock resistance, softness and weight savings. And all this for less money.” Sounds like an offer you can't refuse. Therefore, it is not surprising that some brands are now focusing exclusively on rims without beads. These include industry giants such as Zipp (SRAM) and CADEX (GIANT).

Unfortunately, this is not as simple as it seems. Firstly, wind tunnel tests have not yet demonstrated any significant aerodynamic benefits of rims without beads, as confirmed by Ralf Eggert from DT Swiss: “We carried out aerodynamic tests in cooperation with Swiss Side and compared the performance of rims with and without rims. We couldn't find any aerodynamic advantage with rims without beads. In contrast, our measurements showed that hooked rims have a slight advantage. “Decisive for aerodynamics remains whether the width of the tire and rim are the same, regardless of whether they are hooked or not.

From an aerodynamic point of view, the decisive factor remains the match between the width of the tire and the rim, regardless of whether they are hooked or not.

Secondly, there are rims that are as heavy as top models without side hooks, despite the use of side hooks. Third, the claimed handling benefits are due to the increased volume of air in the tire and lower tire pressure. Both apply equally to hook rims with wide internal fits. “At low pressures, the stability of the sidewalls of the tire on non-slip rims is slightly increased, since the tire carcass is not pressed into it by the bead. But these differences are small and difficult to quantify,” says Patrick Brown, HUNT development engineer, but explains that “feedback from riders and working with our pros suggests a slight advantage.”

What about impact resistance? Ralf Eggert says: “The rim profiles are generally strong. Ultimately, it all depends on the tires and their pressure.” Of course, you can reduce tire pressure so much that any rim breaks.

So, after mentioning these four conditions, all we are left with is the promise of lower prices. However, at €2,900, the Zipp 454 NSW isn't exactly a bargain. The new Black Inc 48/58 is in the same price segment, weighs 100g less than the 454 NSW and has a 23mm internal width like the Zipp. However, Nathan Schickel, SRAM product manager, notes: “Given inflation, the current Firecrest wheelset costs 35% less today than it did in 2019, before we switched to the line's non-lug rims.” . And he adds: “For our NSW wheels, that is, for our top models, we have kept prices the same.”

It turns out that if you question the marketing of beadless rims, it's nothing more than empty words, and even the theoretically cheaper production process is not suitable for every manufacturer: “Larger manufacturers are likely to cut corners. But compared to them, we are still very small players. It's not a big deal for us,” says Patrick Brown.

It would be interesting to see further testing of rims with and without beads with the same internal width and identical tire sets, which would provide comparable data on grip and rolling resistance. However, none of the manufacturers we surveyed were able to provide reliable results. Thus, the jury is still out on whether rims without beads provide significant performance benefits.

Intuitive user experience? No!

On the other side. Since tubeless tires are attached to the rim without beads only by a specially shaped bead ring, the reliability of this connection depends on the correct ratio of tire width, internal rim width and tire pressure. Users of rims without beads must check the compatibility of the rim and tire before installing it, and as a result, they are quickly faced with confusing or unclear safety standards and compatibility charts. In accordance with the ETRTO standard, when installing a tire on a frameless rim, under no circumstances (!) should you exceed the maximum tire pressure of 5 bar or 72.5 psi, even if the tire instructions indicate otherwise – this is very important for the use of the rims without side hooks.

However, tire and rim manufacturers vary in their internal standards and testing procedures before approving a tire for beadless rims. Additionally, there are no binding rules between the participating tire and rim companies governing their jurisdiction. Thus, it remains unclear who is responsible for testing and communicating whether a particular tire is suitable for a particular rim, both from a practical and legal point of view. In the worst case, you may even find conflicting information. SRAM's Nathan Schickel says: “According to the ISO standard, information must be provided by the tire manufacturers.” However, Zipp has compiled its own compatibility chart because it has found that information is not always exchanged as it should be and they cannot rely on tire manufacturer specifications.

Clear standards

Although ISO and ETRTO standards exist, they also raise additional questions. Last year, ETRTO changed its interoperability guidelines. Since then, they have recommended using tires at least 29mm wide only on non-lugged rims with an internal width of 25mm. They didn't bother to explain the reason for this change, although we can assume it's due to the tires coming off the rim.

Which brings us back to Thomas De Gendt's accident. It had a 28mm wide Vittoria Corsa Pro tire mounted on a Zipp 353 NSW rim. The inner width of the tire was 25 mm. Note: Both Zipp and Vittoria approved this tire and rim combination prior to the accident and issued statements after the accident in which they assured the public that the cause of the tire blowout was not a deviation from the ETRTO standard. Instead, it was caused by De Gendt colliding with an object on the road, which caused the rim to break and the tire to subsequently come off it. Shortly thereafter, Zipp changed the 353 NSW tire compatibility requirements to a minimum width of 29mm, bringing them into compliance with the ETRTO standard. However, Nathan Schickel also says: “Because of our existing close relationships with tire brands, there were reasons to continue to approve other sizes.” This is one way to undermine confidence in the standard.

Plus, no one wants to be dependent on a system where a difference of just one millimeter determines whether the tire will stay on the rim or not, especially given the large tolerances inherent in tires.

Lots of unanswered questions

In addition to ETRTO, ISO has also established safety standards for the use of rims without beads. According to ISO specifications, a tire must be able to withstand 110% of the maximum permissible rim pressure without bead grip for five minutes without being lifted off the bead to be considered compliant. On the other hand, ISO states that the tire must be capable of holding 150% of the maximum permissible tire pressure on the bead rim for the same amount of time.

In concrete terms, this means that a soft tire with a maximum allowable pressure of 8.2 bar (120 psi) can be inflated to 12.4 bar (180 psi) before it comes off the bead rim. This permissible value is 4.2 bar (61 psi). However, according to the ISO standard, 110% for rims without beads is allowed if a tire with a maximum pressure of 5 bar (72.5 psi) leaves the rim at 5.5 bar (80 psi). This is a permissible range of only 0.5 bar. According to Ralf Eggert, such pressure differences can occur: “Pressure fluctuations of 0.5-0.6 bar can be achieved quite easily by increasing the ambient temperature or direct sunlight.”

Only the ISO organization knows why they make such a difference between the standards for rims with and without bead rims. Nathan Schickel also comments: “Everyone on our technical team would be happy if the ISO standard were more stringent. Even tire manufacturers always tell us that they consider ISO standards too frivolous. Every company I know of is conducting tests that significantly tighten this standard.”

Accordingly, Schwalbe states on their website that they rely on their own internal testing procedures. Accordingly, they test all products at 1.6 times the maximum allowable tire or rim pressure for 60 minutes. This sounds much more reassuring. However, having to find information about internal testing procedures before making a decision on rims and tires requires a lot of additional effort on the part of the consumer. This is provided that you can find, understand and rely on the information provided by internal testing. Not all brands are as open as Schwalbe. And isn't it enough to make sure your tires are properly sealed, your brakes are pumped, and your transmission, bike computer, power meter, headlights, and radar batteries are charged?

Statements from brands that publicly oppose the use of beadless rims for safety reasons lead to even more uncertainty. Ralf Eggert from DT Swiss said in our interview: “We do not compromise in terms of safety. That’s why we make more complex decisions when it comes to making bead-toe rims for our high-pressure wheels, i.e. road bikes.”

So it can be incredibly dangerous if bikes come standard with rims without beads and end users without sufficient technical knowledge and experience are not even aware of this, let alone the special requirements for such rims. Dealers must combat this by educating and counseling their customers.

Stay on rims with bead hooks

Although beadless rims do not necessarily pose a safety risk when used correctly, many questions remain unanswered and it is difficult to identify any significant benefits to the rider. Rather, we get the impression that some brands are seeking greater profit at the expense of safety by producing rims without beads, at least for their high-end products.

Riders who don't want to limit themselves in tire selection or spend an entire day researching optimal tire pressure, tire width, and internal rim width should choose bead-toe rims. But if you really want the full package when it comes to modern bike technology, you're always looking for even the smallest advantages, and you're not afraid to take the time to educate yourself, you can happily opt for rims without beads. “When used correctly, the system works,” says Even Ralf Eggert.

In any case, I would advise you to do your own research and rely on manufacturers to be transparent about which products are compatible with each other, so that you don't end up with your bike leaning against a guardrail with a flat tire and you lying next to it. him.