mikehhhhhhh wrote: ↑Mon May 27, 2024 12:38 pm
I found this point salient - the translation isn't good, but it seems like they tested a load of combinations and only had one blow off - a Corsa Pro on Zipp 303 at double the rated pressure with "assembly fluid" (unsure if this is some mounting lubrication or a very bad translation for sealant)
"We tested some combinations of tires and rims with static overpressure tests in the DT Swiss laboratory and measured the wheels for dimensional accuracy. Result: All wheels are within the standard, all tires or Rim pairings passed the jump test. Only with double nominal pressure - i.e. 10 bar - and use of assembly fluid did the tire jump off in the pairing Zipp 303/Vittoria Corsa Pro 28 mm."
That is for the
static test. Completely misleading that is what you took away from the article.
The result for the dynamic test:
"We subjected some tire-wheel combinations to a puncture test with the tire rolling - using a test setup that we designed specifically for this purpose. This dynamic test was intended to determine whether tires could be pulled off the rim by shock loads. Result: The dynamic impacts could not pull the tires off the rims; even critical rim-tire combinations endured oblique impacts at a pressure just below the static release pressure without the tires jumping off.
But that doesn't mean that shocks aren't a problem per se. Presumably the conditions of our test are not sufficiently sharp - our impact speed is only 17.5 km/h due to the limited start-up."
Also note the dynamic test is only in relation to the DeGhent incident. It does not account for a dynamic blowoff as has happend to riders where a puncture did not happen.
Also you forgot to mention these salient points in the article:
"
Problems:
the standard is inadequate and does not guarantee safety
Manufacturers test harder, but not uniformly
Hookless products are not labeled uniformly
From a technical point of view it would be much better. If the tire's characteristics were also given - nominal size and maximum elongation of the core with a pressure safety margin of, for example, 160 percent - then the issue of tire bounce would probably not exist at all, and every tire that is clearly marked as hookless-capable would be safe on a dimensionally accurate hookless -Rim.
Unfortunately, in practice this is not always the case. According to our research, falling tires at Hookless are not a mass phenomenon, but there are examples - including in letters from readers. The risk of misuse is real. A tire industry insider told us: “Many people don’t even know they ride hookless. The products of small manufacturers are more widespread than you think. If the wrong tire is mounted, there will be a bang.”
However, if the rims and tires come from a single source, like Giant (brand name Cadex), safety is likely to be relatively high.
However, for many rim manufacturers this is not safe enough. DT Swiss, for example, the largest in the industry, does not build hookless rims for tires less than 33 millimeters wide. Philipp Lüdi, head of the DT test laboratory, explains this as follows: “We have to take obvious misuse into account. These include pressures that are too high or tires that are not approved for hookless.”
And this approval is actually a big problem in the racing bike scene, which is happy to tinker and swap, where people like to combine materials according to their own taste. Because here each manufacturer cooks their own soup, and the labeling of the products is not clear. There are compatibility lists on the wheel manufacturer's websites showing which tires are permitted on which rims. These lists are based on static overpressure tests, but as samples they can only provide an indication of which pairing works. Missing tires from the lists raise questions: Have they not been tested or have they failed?
This is where the crucial weakness of the standard becomes apparent: the tire is not defined at all - except that it should fit the rim - and the pressure safety is specified far too loosely.
The fact that the standard is so lax is probably primarily due to economic reasons. Lightweight and very stiff tire cores made from Zylon, which are stiffer than the usual aramid core, are so expensive that manufacturers do not use them widely.
In summary: The situation is unsatisfactory because it is confusing. The best solution would be a binding and sensible standard that sets the safety level so high, even without hooks on the rim flange, that tire jumps are ruled out. There should also be clear and easy-to-read labeling of the rim and tire. No tiny writing, black on black on the side of the tire.
With low tire pressure - on gravel and mountain bikes - hookless already works well today, as long as you don't overdo it. Anyone who pumps 2.4 inch wide slippers on a current mountain bike rim to 3.5 bar, i.e. about 2 bar more than sensible, is exceeding the pressure limits of the rim and risking it exploding.
The fact that the tire pressure on racing bikes has been reduced thanks to wider tires and rims is a win. Because these combinations are nicer to drive than the narrow high-pressure tires of the past. The progress is perhaps indirectly due to the precisely named upper limits for the hookless system: a maximum of 5 bar on the racing bike clearly signals that something has changed. But floor pumps easily give a lot more, and 7 to 8 bar in racing bike tires was relatively normal until recently.
It will probably take some time before hookless establishes itself as a foolproof technique. Industry veteran and technology pioneer Josh Poertner, the boss of Silca, believes that the system will prevail, because so far every advantageous production method has prevailed in the long term, he said in a conversation with Dan Empfield from Slowtwitch. Until then, it's important to keep your eyes open when choosing tires and keep the pressure low. Or continue to drive conventional rims, there's a lot on offer."
