Zipp understand this subject better than any commenter on this thread.
I would also wager that the discussion on minimum tyre width is taking time to resolve because their current chart reports what tyre manufacturers say is safe.
I dont believe this is accurate at ALL.
The only thing that should affect the level of force pushing the sidewall is the psi in the tire itself. Meaning, only air pushing directly against inside of the tire directly in contact with the rim sidewall will have an effect.
The rest of the tire would work to pull the bead UP, off the rim bed, not push it sideways, because the top of the rim would serve as a pivot point for the rubber.
Not clear if this is because they think 30mm is minimum safe size on those rims, or because of the shitstorm thatās unfolded after these incidents; if their teams are on 30s and have blowouts they can just say āthey were following ISO/ETRTO 
ā
But the ISO standard says 29 is OK, so why would they tell them to go to 30 when possible if itās just to say they met the standard? The logic doesnāt work out unless they actually think width is an issue. And why would they say they are considering whether to change for consumers too?
No one makes a 29, so it is likely easier to just say 30.
Thereās nothing stopping anyone from making a 29 though, and tire sponsors tend to develop racing tires considering pro teamsā needs. And since the ETRTO specifies 29 as the minimum safe combo, presumably thereās a market for it.
Plus, Zipp didnāt say use 29 minimum, 30 if you need to. They said use 30 if possible. Which again is still a minimum. Theyāre fine going 35 if desired.
Incorrect. The geometry (angle of tire wall relative to rim wall, plus shape of rim wall, and even tire bead geometry) matters a lot to the net force the air applies.
Tell me, why canāt I run a 20mm diameter tire on a 25IW rim? Hint, the tire will fit since tire width when laid flat is ~2.5x the diameter, so that 20mm labeled tire is 50mm wide when flattened. It can reach across that 25IW rim just fine and still be mostly circular.
After all this has been thoroughly discussed and the myriad facts laid out it is an absolute no go for my own money and skin and bone. There are too many limitations with respect to pressures and tire widths that are safe to use before getting into the ISO spec requirements that are critical to adhere to. Rims can in theory be made stronger but in my own experience , rims were already very robust. I donāt see where the advantages outweigh the risks.
I must be the only person I know thats popped a tyre off a hooked clincher. I have old now 404 nsw which are 17mm internal I think, fitted 26mm turbo cottons to it one time and they popped off by the side of the road after fixing a puncture. 23-25mm is the advice for them and I didnāt really know any different.
In 2007 I popped a brand new Bontrager ACX 26x2 tubeless mountain bike tyre off a Mavic Crossland UST rim just riding along on a slightly rooty trail
Plenty of people have had tyres pop off hooked rims.
Itās just not a hot topic right now, so isnāt being discussed.
I think hookless is perfectly safe when everything works, the challenge for me is that the margin for error is significantly reduced from a hooked rim and Iām struggling to quantify the benefits I gain from reducing my safety margin.
I get why the manufacturers want to make more margin but Iām still only buying hooked rims.
Please donāt bring facts into the strawman discussion. 
Iāve not seen any evidence of a tyre just magically coming off, though?
Iāve seen pros riding on flats leading to the tyre coming off.
Iāve seen the two cases where the rim was damaged leading to the tyre coming off.
Thatās precisely my point. Hookless is perfectly fine, but your tire choices are drastically reduced. Plus the care with pressure is another issue for some - not for me.
I went hookless knowing the drawbacks. The benefits, in this case, were purely price and conditions to pay.
Iām sure Josh is a reliable source. But an anecdote isnāt evidence.
Even if you want to take his comments at face value, we have no idea what these tyres were pumped up to, which brands, were they prototypes, how many times had these tyres been fitted and removed, had they been damaged etc etc.
Weāve already seen one small European brand making hookless wheels that are out of spec making a lot of noise on YouTube. You canāt blame a standard if people are making out of spec wheels.
Hard to disagree that the ETRTO spec is insufficient.
However, cycling news posted an article a couple of weeks back asking wheel and tyre manufacturers about their testing protocols.
All of them were testing in some way or another upto 150% and one even claimed that hookless blowoff pressures were within 20psi of hooked.
Last week Zipp was āour internal data shows that these wheels are great with 28mm tires and fast too, sucks eggs ERTOā.
This week Zipp has changed their tune to āyou better use at least 30mm tires on our rimsā and sorry for the drop in aero efficiency that you paid for but have now lost.
I did when I was young and thought that 140psi was faster. Short of over inflation or getting a tire installed slightly crooked I havenāt seen tire blow off of a regular rim in 40+ years of riding and racing.
The issue is frequency. Joshās anecdotal data and other data from people that have posted seem to show incidences in the single digits (<5%). A tire coming off a hooked rim for no reason is like a 1 in 10,000 event.
The hookless apologists crack me up. They made the mistake of buying hookless rims and now have to defend the system to the death on the internet. āShow me the data!ā, they say. Itās like the anti-seatbelt studies trying to show that seatbelts did not save lives.
I think you guys are putting too much consideration into 1 conversation - itās not a scientific article of any sort, itās a āconversationā published on the internet.
Iām not saying heās lying, but hey, take it easy. All your eggs look like in one basket, and this basket doesnāt look too firm.
I havent seen anyone dismiss anything or anyone.
Arguing that you dont need absolute certainty on an issue, or that the most safe option is not
necessarilly better than safe enough, or that there is a relative lack of evidence, is not the same as dismissing someone. This is the definition of discussion.