Hookless and updated ISO Standards - Thomas De Gendt Crash

[commendatore]

I saw a few threads this might fit under, but thought it worthy of a new one here.


https://escapecollective.com/thomas-de- ... ng-to-all/

I'm going to repurpose a set of Zipp 303s for road use and found the article above pretty timely as I started down the rabbit hole of ordering tires. I've been very happy with each generation of the tubeless GP 5000 and did a quick search to see what tire size I should run for these wheels (25mm internal). Zipp specifically calls out 28mm tires ok, while ISO now says you need a labled 29mm minimum.

For Mr. De Gendt, my own experience tells me that vittoria still runs smaller than continental. Many factors at play, I'm sure.

[Mr.Gib]

I wonder if the air liner is partially the cause of De Gendt tire blow-off.

An air liner consumes most of the volume inside a tire. If a tire hits an obstruction (such as the edge of a pothole or similar), the tire will compress at the point of impact which will reduced the volume in the tire forcing the internal air pressure to rise. With an air liner installed, the amount of air volume available to "absorb" the increased pressure from the tire compression is drastically reduced. Could this lead to a sudden spike in air pressure that causes a blow-off? The sudden increase in pressure may be great for protecting the rim from contact with an obstacle, but maybe not so good when it comes to keeping the tire on the rim.

[spdntrxi]

^ I have my doubts on that one.

[Nereth]

I feel like the pressure spike from hitting an obstruction can't be more than a few PSI... speculating.... it might reduce the cross sectional area of the tyre above the hooks (so even if we pretend the entire rim bed is filled by the airliner) by like... half, but it only does that to at most say, a 60-70mm length of tyre out of a 2.1m circumference, so that's now 50% loss in volume on (70mm/2100mm)=3.3% of the tyre periphery = 1.4% total loss in volume. On 60-70PSI that is ~ 1 PSI raise in pressure.

The pressure rise doesn't seem significant. The impact loads also act to unload the bead and make it less likely to want to jump clear, at least in the vicinity of the impact.

Cornering loads actually trying to rip the bead clean off seem more significant. Not that there were any visible cornering loads there.

The sun heating the tyre and thus the air pressure rising from that would also be more significant.

[mikehhhhhhh]

303s or firecrest?

The 303s is 23mm internal, so fine with 28mm, no question.

I've been running 28s on my front 353nsw (25IW) and all the fuss has me thinking about putting a 30mm on for peace of mind.

[Lina]

Let's add the two other hookless (also Zipp but with Continental) blowouts from this season here. Both of these without liners.

viewtopic.php?f=132&t=172868#p1849395
viewtopic.php?f=132&t=172868#p1849412

[xiyuwang]

I wonder if the air liner is partially the cause of De Gendt tire blow-off.

An air liner consumes most of the volume inside a tire. If a tire hits an obstruction (such as the edge of a pothole or similar), the tire will compress at the point of impact which will reduced the volume in the tire forcing the internal air pressure to rise. With an air liner installed, the amount of air volume available to "absorb" the increased pressure from the tire compression is drastically reduced. Could this lead to a sudden spike in air pressure that causes a blow-off? The sudden increase in pressure may be great for protecting the rim from contact with an obstacle, but maybe not so good when it comes to keeping the tire on the rim.

Is the air liner actually some sorts of foam? Air can get in them, so it is not taking 100% of the volume.

[mikehhhhhhh]

Let's add the two other hookless (also Zipp but with Continental) blowouts from this season here. Both of these without liners.

viewtopic.php?f=132&t=172868#p1849395
viewtopic.php?f=132&t=172868#p1849412

We should throw in Derek Gee's and Fred Wright's tyres coming off the rim, both in Roubaix '23 - neither of which seem to be using hookless rims.

They were they fault of tubeless at the time and their hooks didn't save them.

It seems to me that failures happen all the time, but people are blind to the past and will use each new failure on new tech.

[Attermann]

Let's add the two other hookless (also Zipp but with Continental) blowouts from this season here. Both of these without liners.

viewtopic.php?f=132&t=172868#p1849395
viewtopic.php?f=132&t=172868#p1849412

I believe the first one is Mathias Norsgaard, he has said himself that he hit a pothole and flatted both tyres.

[commendatore]

303s or firecrest?

The 303s is 23mm internal, so fine with 28mm, no question.

I've been running 28s on my front 353nsw (25IW) and all the fuss has me thinking about putting a 30mm on for peace of mind.

303 firecrest. I've got extra 28's on a shelf but I guess I'm ordering 30's as well!

[spdntrxi]

303s or firecrest?

The 303s is 23mm internal, so fine with 28mm, no question.

I've been running 28s on my front 353nsw (25IW) and all the fuss has me thinking about putting a 30mm on for peace of mind.

303 firecrest. I've got extra 28's on a shelf but I guess I'm ordering 30's as well!

if 303 is 23IW...you should be fine with 28mm tires. The 353 NSW are 25IW.

[apr46]

I sort of disagree with the notion that hitting an obstruction couldnt lead to bead instability causing the deflation. The role of the hook isnt to hold the tire in place, as the proponents of hookless often point out, it doesnt do that. What a bead hook does do is distribute the forces that could cause bead instability over a wider area reducing the chances of an issue. This is pressure related in that a higher presure poses more risk for this kind of instability. It also means that the hook bead interface needs to work well for the hooked rim to be "safer" and I am not convinced that some of the "mini hook" designs actually do that.

I am of the opinion that an ideal hookless rim with an ideal tire for that rim is probably theoretically as "safe" as an ideal hooked rim with a tire ideal for that rim. That said, we live in the real world it seems like rim and tire companies are very far from ideal. I personally will continue to seek out hooked rims.

The liner compresses under pressure (i.e., its also compressed volume and the "pressure" it exerts is relflected in the PSI of of the tire since that is a measure force exerted on the interior area of the tire / rim), so its probably not a factor unless it interferes with the way the tire is expected to interface with the rim in which case, the liners need to be scrutinized. I personally have avoided liners partly because they seem like a lot of work and partly because I have yet to get my head around how, as an installer, I would ensure that the liner wasnt causing a potential issue.

[mikehhhhhhh]

303s or firecrest?

The 303s is 23mm internal, so fine with 28mm, no question.

I've been running 28s on my front 353nsw (25IW) and all the fuss has me thinking about putting a 30mm on for peace of mind.

303 firecrest. I've got extra 28's on a shelf but I guess I'm ordering 30's as well!

I'm fortunate in that I have some hooked rims I can use the 28s on.

Frustrating, because I don't believe hookless are dangerous but going to 30s does feel like good risk mitigation.

[toxin]

The ideal hookless tire and would have a metal bead that would require a machine to put on

[spartacus]

An air liner consumes most of the volume inside a tire.

It was my impression that the air prressure inside the tire compresses the liner significantly.