flx100

Tire blew off the rear rim - second time this summer.
Both instances have been the new Veloflex Corsa EVO 25mm on HUNT carbon disc wheels - internal width of 19mm. Both have been AFTER riding several hundred kilometres.
Veloflex does show the ETRTO compatibillity table in the instructions - stating that you can use up to 17mm internal width with 25mm tires.

I'm still surprised by this, especially because the tires were tough to install. Have anyone experienced the same with either HUNT wheels or Veloflex tires? Or both?

I used Vittoria latex inner tubes size 25-28mm, and they seem to be too large, and difficult to properly fit inside the tire, even with baby powder. If i had pinched some tube under the bead, wouldn't that have caused it to puncture sooner? Or even as i inflated the first time?
I wonder if i should try a smaller size inner tube?

The Veloflex tires are otherwise fantastic, by the way, and much cheaper than comparable tires, like Vittoria or Specialized Turbo Cotton.

smashndash

Don’t pin this on “wide rims”. I use 25mm tires on 23mm rims and would say that is probably the maximum.

It’s tough to say whether the tire blew off on its own or if the tube blew and the tire blew off as a result. I’ve seen the latter happen before. Never seen the former. I also would not reuse a tire that as blown off.

And it’s not certain that an excessively large tube would blow immediately. Yes, a pinched tube probably would but if there was a chafing of some sort then that would take a while to manifest.

masi61

Just curious: what type of rim bead do the Hunt carbon disc rims have?

flx100

I should have specified, i did not reuse the tire.

The HUNT rims have a hooked side, and they have the little notches to 'hold' tubeless tires. They make the tires (also non-tubeless) snap into place as you inflate.

flx100

I also want to note, that i'm really hoping i can get some assurance that it must have been bad installation that did it - and not the tire/rim combination. I really like Veloflex: Great tires - great comfort, grip and feel, and look great too. I have used Master in the past. And the factory is mostly woman-operated and in a part of Italy that was hard hit by Covid. So i like to support the company as well!
I love the Hunt wheels too - super light weight, and clean look.

shelbyfv

If two different tires blew off in the same manner, I don't think you should expect anything different in the future I think Hunt says as narrow as a 23mm tire on their 20mm internal carbon rim but something about your combo isn't working. Interesting problem, keep us posted.

HTupolev

A tube can't "blow" inside of a tire, there's nowhere for it to blow to. If a tube starts leaking, the escaping pressure won't blow the tire, because the tire was what was containing the pressure in the first place. If the tube leaks and the tire goes flat, this can result in a rolled tire, but I wouldn't describe that as "blowing."

Tubes do generally end up shredded after a blow-off event because the inner tube cannot contain high pressure without being constrained by the tire. The tire blows, and then the tube starts expanding into the now-open space until it pops, succumbing to the same fate as an overfilled party balloon.

smashndash

It can happen because I’ve seen it happen. Someone installed a tube with the lockring inside and the tube blew. The tire blew off the rim and the bead separated from the carcass. A leak is not the same as a rupture.

HTupolev

How do you know that the tube blew before the tire did?

smashndash

Because they had installed the tube only a couple of miles before. And the odds of a tire randomly choosing to blow are quite low relative to a lockring cutting into the tube.

HTupolev

Unless the tire wasn't seated properly on the rim, which seems extremely possible given that you're saying that the person who installed it did so with the lockring inside of the tire. If the rim profile is not wide, the lockring might even directly cause the tire damage by cutting into the tire right above the bead. (And the reason I'd suspect this is that the casing separating from the bead is the really puzzling part of the story. Tire casings are what contain pressure; if the air in the tube moves outside of the tube, it doesn't cause the tire sidewall to have to deal with significantly higher tension.)

smashndash

Hm. Fair enough. But wouldn’t the tube rupturing at a particular point cause a concentrated rush of air? I’m thinking that the air trying to escape from that particular spot would be enough to lift a small portion of the bead over the rim wall. Could be wrong.

Basically, what would happen if you tried to use one of those airshot tubeless inflators on a non-tubeless tire? There’s a reason why we don’t run clincher tires tubeless. My claim is that a sudden rupture of the tube (without a similar cut in the tire) would turn your setup from a tubed one to a tubeless one.

HTupolev

The physics around that are more complicated than my knowledge can give a good answer to. But if the bead blew off due to escaping air beneath, it's unclear to me why the casing would separate from the bead.

There are two main reasons that we don't run tube-specific tires tubeless.
1-Non-tubeless tires are often highly air-permeable, sometimes even with sealant.
2-Inner tubes help significantly with tire bead retention on the rim. Consequentially, tubeless setups require stiffer beads and more precise tolerances between rim and tire to be safe against blow-offs.

Point #2 could possibly explain why a rupture of an inner tube could cause a blow-off, assuming that the inner tube separated from the bead and rim bed before tension was lost in the tire casing. However, it still doesn't explain why the casing would separate from the bead: it's good safe practice to toss a tire after it has blown off a rim, but blow-offs typically don't create rips in tire casing.

flx100

Thanks for the great input.
I agree with the theory that a tube can't simply blow inside a tire. It must have 'gotten out', so to speak.
I think in my case, one of two things happened:
1. This specific tire and rim combination simply is not compatible, and the tire slipped off the rim.
- Maybe too much baby powder during installation made the bead slippery?
2. Bad installation.
- Tube was too large, given the wide rim the tire sits wide leading to a smaller overall diameter.
- Tube then got pinched under the bead of the tire and the air was able to slip under the bead and out in the part of the tube stuck outside the bead. But this wouldn't necessarily cause the tire to come off the rim?

After both blowouts, the tires looked structurally fine - came off the rim clean both times.
Either way, I will not use this combination again, which is a bummer.

flx100

Oh, and finally, i should say, i'm not super heavy. I weigh 76kg and i pump the rear tire to 100psi.