be careful when airing up tractor tires

I was reading about a fellow on the drag racing forum that was airing up a tractor tire and it exploded, blew out windows across the street, he has lost one leg, has liver damage and is in a coma.

     Man, that is a shame, terrible accident. Definitely will be praying for him !!!

That is sad to hear. But he must have exceded the 12 to 14 psi limit to explode like that. Wish him a speedy recovery, Bob

a guy in our old car club was inflating a tire on his Model T and when it blew up it took off the tips of a few of his fingers, he was very lucky

if i aint mistaken 14 pounds per square inch...aint there alot of square inches in a tire like that ?

Your calculation is correct-  One square foot of surface is 12x12 or 144 square inches.  Multiply by 14psi, and you have 2016lbs of force.

Now, a single ply of low-grade steel cord in the sidewall will present AT MINIMUM, an average tensile strength of over 12,000psi.  A 4-ply tire sidewall will yield at around 50,000psi.

What we have, under this type of a circumstance, is either a very, very, very, very serious failure of the bead overlap or bead section shape, or a failure of the rim... AND an extreme applied pressure... and I'll stress EXTREME.  This kind of thing happens at AN ORDER OF MAGNITUDE higher than rated pressure... like... 120psi instead of 12psi.

If you take a tractor tire, pump it to 20psi, and then stab a big hole in it... HARD... the air will rush out.  If you drive over a sharp metal spike, same result.  If you put sideways force on the spike, the tire's structure will deflect and UNSEAT THE BEAD before causing a rupture, and in doing so, the tire just goes flat.

The most common mistake in a tire rupture, is as noted- the 'lock on' type air chuck, typically connected to an unregulated bulk high-pressure compressor.  The PROPER way, if using a lock-on, is to have a regulator set to a desired pressure, followed by a pressure relief valve set to slightly above max.  That way, lock it on, and walk away, it will not present a pressure problem.

The second most common, is to misjudge the amount of time it takes to charge up a tire.  If the tire is NOT ballasted, the volume of airspace available to pressurize is quite large, so you'll be filling for a good long time... you'll sit there with the air hose for 20 minutes or so before making just a few pounds' change.  IF the tire is loaded with fluid, however, the available space is very small, so the air-charge time is very short.  A tire that's totally filled with ballast will go from atmospheric, to full air reservoir pressure in literally... a heartbeat.

There is one interesting problem that occurs under certain circumstances, but I don't think it really applies here... but it's called "diesel effect".  Say you spray some volatile compound into a closed chamber, and then apply air-pressure RAPIDLY to the chamber... the volatile compound, given the proper conditions, will ignite, just like Herr Diesel described in his 'heat-engine' thesis.  hard to make that kind of pressure rise with a tractor tire... too much volume, not enough airflow, and not high enough pressure... but IF there was a volatile compound in the tire, and something ELSE happened to ignite it (static electricity?), then you could get an incredibly high pressure, very quickly.

If there were more detailed pictures, it would be easier to identify the failure, but my gut feeling, based on what I CAN see, is that excessive pressure caused the bead-wrap to fail, stripping the sidewall plies away from the beading wire.

The only question left, is wether the bead of the tire was  improperly wrapped, or if the rubber formula or process was not properly done.  Frankly, with many of these imported tires, I wouldn't be surprised to see something like this happen, but that machine looks awfully new and green for carrying low-budget imported tires.

Important to realize that once the tire BEGINS to rupture, the tire starts losing pressure immediately... and in doing so, there is insufficient sidewall pressure to continue a rupture.  In order to come apart as you see here, the bead has to fail around most of the circumference simultaneously.  A tube-type tire will go a little bit further, simply because the tube causes a high-stress edge, but at that much force, the tube will rupture so soon, that a circumferential rupture cannot fully 'wrap'.

Back when lock-rings were VERY common, guys would get killed by being cut in half by a lockring that became unseated and popped off the rim.  Even still, the need for putting tires in a cage when mounting up, is of critical importance... and it's because the tire is applied very high pressures from the git-go.  The most likely time for a tire bead or bead-seating failure, is on the very first air-up after a mounting or re-mounting action.  Many guys would get in a rush, and instead of swabbing down the bead with lubricant or sealer, would mount 'em dry, and just overpressure to get the bead seated.  better to soapy-water 'em so they slip into place without substantial strain.

I feel sorry for the poor guy, but this didn't have to happen as it did.  I hope the insurance adjusters investigate to extreme detail, and if they find a tire manufacture issue, it gets resolved quickly.  Nobody needs a tire so cheap that it's dangerous.

Dave K -- very interesting explanation, I used to work with a guy that sprayed either insid  11r22.5's and throw a match in there to get them seated on the bead, I refused to stay in shop when he did this, your explosive mixture theory I feel should be checked out!

If possiable, when mounting tires on vehicle place lock ring to inside.I have seen wheels explode while they are being mounted long after they were aired up. Also they should be treated with care when being moved around, loaded in back of pickup,ect!

A neighbor and friend of mine was killed by a split rim truck tire 20 years ago almost to the day. It was the inside dual on a flatbed truck he was filling when it blew. It stripped the studs that held the outside wheel on and the outside wheel and inside ring caught him in the head and nearly removed his entire face and threw him up against and flattened to the ground a nearby gasoline pump. He was 19. Not a good day.

Years ago when those 'fix a flat tire in a can ' came out it took awhile but eventually someone got killed. The tire kid or mechanic at a shop was told to put a plug into a tire a customer came in with.Customer didn't think of telling anyone he'd 'fixed the flat' with one of those spray bombs( heck..who would ??). When the gut put the tool in to clean out the hole, he either hit the cord(steel belted radial) or scraped the nail.BAMM... tossed him against the wall( I think he died),other's lost hearing for a few days. It took the government a few months to ban the cans. Seems they used isobutane and propane to propellthe patching 'slime' into the tire!

Early in my career I worked at a Firestone and a Goodyear tire shop. We had a guy at the Firestone shop get knocked out and a gash in his head from flying debris. Tim was breaking down a tire that had fix-a-flat in it. One spark was all it took. It was like a bomb went off. Broke lights and windows. Later when I got bumped by seniority, I went around the corner to the Goodyear shop. One of the commercial guys had a split rim come apart in the cage while he was airing it up. Another one had a bus tire sidewall fail while he was filling it. They called it a zipper type failure. Best I can describe is it sounded like ripping a shirt and a loud whoosh. It put the guy on his back. Then there was the day I mounted 6 new Goodyear Wrangler radials before I found a good one. One of them had that shirt ripping sound. I can say I really don't miss working in a tire shop anymore.

I have aired lot of tires over theyears and luckily never had one explode. However, I have an old 357 grinder mixer that has old truck tires on it. Went up stairs in the barn to throw down some hay and noticed grinder setting cockeyed. Tire had exploded just sitting there. If you had been standing beside it could have been bad. Had tire pieces all over the barn floor. Bill

I like your Dad's quote Dave. Lots of truth in that. I still don't miss the tire shops, and I don't go out of my way to sell tires here. Long ago when you still saw split rims fairly common, and I saw that one blow while filling, I refused to work on any of them any more.

Removing the valve stem isn't enough when welding on a rim. The tire has to be off too. Welding heat starts a reaction in the rubber which will make it explode with the valve stem removed too.

There have been videos on that topic,
http://www.youtube.com/watch?v=pNZ4siYGkag may be one.

Gerald J.

"Accidents don't happen for one reason-  they happen as a result of several things all happening at the same time.  Usually, many people are involved, and no one single reason makes it all happen, but when it's time, all the pieces are in place, and it happens."

DaveKamp, your Dad was very correct. In every safety course I have been through and every serious accident I have reviewed I have learned that it takes several things coming together at the same time for a serious accident to occur. If the small accidents start happening on a regular basis the big one is not far behind. Attitude has a great deal to do with safety. If the supervisors in an organization ignore the little safety violations and do not correct the things that contribute to an accident the big one is going to occur.



Edited by Hubert (Ga)engine7 - 29 Jul 2011 at 9:19pm