I've got the new Stans a340's (24/28 CXrays with alchemy hubs, 2 layers of Stan's yellow tape) and have been using Pro3's with Conti butyl tubes since late spring. I haven't had any problems at all, and actually found them no harder to mount (and perhaps a bit easier) than my Fulcrum 3's. I'm pretty light (59.5kg) and have been inflating them to only 85psi front and 90 rear, and they have been great.

It makes sense. The tyre popped off the rim after a ride that involved a very steep descent, and I was hung over so I was braking lots! About 4 hours later, the tyre popped off and the tube exploded.

When I removed my tyres last night, the front one need levers to remove (it is relatively new) but that rear came off easily (quite a worn one)

Anyway, rode earlier on the pro race 3s with no issues!

I've been using Conti GP4000s for 1.5 years, original lighter rims, red veloplugs. No problems at all. But I never use over 6.5 bar, sometimes <6. The shelf on the rim under the bead hook can make it easy to catch the tube and not be all that obvious and I think that may be a factor.

Maybe... but that should blow off the tire pretty quickly... not after a month of riding.

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formerly rruff...

I got my ultremo zx and did the same: gave them 8 bar and no pop off. I noticed that the diameter on the zx also seamed smaller than the durano s and a bit tighter. I have som veloflex master 22 that I tried to put on they are so hard to put on these wheels that I will not use in case I get a flat but they seamed to be sitting very well on the rim

I'm no so sure about your theory about the tire bead stretching and tearing. Not just because Kevlar is very strong fiber, but also because tire retention does not depend on the circumferential strength of the bead - it relies on the strength of the 'clinch' between the bead and hooked rim sidewall. Even if the bead is completely broken, the clinch will keep the tire on the rim.

How do we know this? Two reasons. Firstly, here's an experiment that you can try yourself, involving purposely cutting a tire bead and installing the tire:

http://sheldonbrown.com/rinard/tirebead.htm

I've repeated this test myself, only I cut each tire bead in 8 equally spaced locations. After mounting the tire, I inflated it to 140 psi and let it is sit overnight. The next morning, the tire was still on the rim. I then lowered the pressure to a normal riding pressure (100 psi) and went for a 30 mile, with several hard corners and quick stops. The tire stayed on the rim perfectly fine, even though the bead was severed in many places and had zero circumference strength.

The other reason we know that tire bead strength isn't required is from the observation of changes in spoke tension when inflating a tire. As many have reported, spoke tension decreases with tire pressure. This is because the tire is is squeezing the rim circumferentially, compressing the rim and relieving spoke tension. Bead tensile strength would be important if the tire pulled outward under pressure, but instead the pressure causes the tire to squeeze inward, making the circumferential tensile strength of the bead superfluous.

(So, one might be wondering how a tire can blow off a rim if pneumatic pressure causes it squeeze onto the rim harder. When a tire blows off a rim, it is not because the tire is pulled out off the rim radially, it is because the tension in the tire casing pulling in the lateral direction causes a portion of the bead to be slid laterally out of the rim. In other words, the pneumatic pressure causes the tire to want to become fatter, pulling the tire beads apart. Well, it would, except that the clinch between the bead and the rim sidewall locks the bead in place, preventing it from being pulled out.)

As for the Alpha 340 rim, I'm wondering if the problem isn't the internal geometry of the rim prevents the tire bead from seating under the hook properly, providing an insufficient 'clinch' to keep the tire on. Maybe the shape of the bead area of certain tires doesn't fit well with the Alpha 340's internal sidewall/hook geometry, making these tires more likely to blow off the rim.