Tire mounting (airhead list)

[Air4Life]

I've been following the "Tire Mounting" and its variant threads on the airhead list.  The following link was posted there and I thought it especially important to share.

http://themotolady.com/post/36861492728/monster-project-tire-explosion

These were not new tires she was mounting, they were "take-offs".  This detail piqued my interest as I was thinking about my not so long ago tire changes.  I had removed my rear prematurely, but had not really thought about using it again.  I broke the bead from the rim using a small woodworkers vice (~ 6 inch x 4 inch) and then pried the bead off the rim with the spoon.  While doing this it did occur to me that the tire bead must be succumbing to some forces its not really designed for.  This had me thinking of the people who at times swap their own tires on and off.  

I am wondering if this could have been a contributing factor in her case - maybe even a significant factor?

[k_enn]

If you try to "gorilla" a tire off the rim on our wheels without getting the opposite side deep into the "well" of the wheel on the other side, you may well be subjecting the bead to more force than is prudent.  But if you get it deep into the well opposite from where you are spooning, you should be nowhere near the force needed to damage the bead to the point where it would break.  Other wheels may be different.

[Barry]

I read that thread on the airheads list and while I agree over pressurising a tire is obviously dangerous and the lady had a lucky escape I was very surprised to see it fail at the bead reinforcement. Having cut through several tire beads I would say the tensile strength of the the bead wire is many tonnes. It must have been damaged but even that's not easy. Try it net time you replace a tire.

[tvrla]

Yeah, the steel chord in the bead is strong enough to tow a full size car!

No way did that have anything to do with re-installing a used tire!

[Barry]

I'm sure wirespokes will tell you himself but what I think he was saying is that it would be near impossible to damage the bead wire to the extent it would fail just by installing a used tire. The bead wire must have been damaged some other way. I'd be surprised if overpressurization would ever lead to a sound tire bead being the first thing to fail. The bead wire is so incredibly strong that you can't hardly stretch it a fraction never mind break it.

I've always assumed that an over pressurised tire would go bang some place else that is not reinforced with a thick steel wire, probably the sidewall.

I guess we all would have some concern at the pressures sometimes needed to seat the bead. I do wonder though if the max safe pressure is the same for a static tire as it is for one on the road. I've heard of tires being inflated to double the max. safe pressure and still not go bang.  Not me, I wouldn't go that high but I sometimes have had to exceed the max before the beads seated. Seems sensible to throw something like a tarpaulin over the tire and stand well back just in case something does give as the pressure rises.  

[tvrla]

Barry is spot-on as always! I definitely don't see how that cable can break - as a matter of fact, I have no plausible explanation for that damage. It's beyond me.

As for seating the bead, I've had to go as high as fifty or sixty psi pressure in the past, but since I've been using real honest-t0-goodness tire lube, even tubeless tires seat with the hand pump at 30 psi. Wonderful stuff!

[Motu]

A commercial tyre machine puts much more strain on the beads than your puny arms and little tyre levers.