I read in an RV forum where someone was changing from one brand tire to another brand. One reason given for the brand change was because they had suffered two “zipper” failures with their 22.5″ steel body radial tires.
In my blog I had suggested that a “zipper” failure can occur with any brand steel body radial. NOTE the SAFETY WARNING if the steel body tire has been run at lower than 80% of the required air pressure. DO NOT REINFLATE the tire unless it has been dismounted and inspected by a dealer for that brand of tire.
What is a zipper rupture
As I try to support my statements with more than just my opinion, I dug out an article from Tire Business magazine. In that article it was pointed out that “circumferential fatigue ruptures, known in the trade as ‘zippers’ in steel radial truck tires,” are a failure that can have serious safety consequences and are not just an inconvenience to the RV traveler.
The article goes on to point out that “a zipper rupture is a tire failure in which the tire blows out in the upper sidewall, leaving an even line of broken steel cords exposed, which gives it the appearance of an open zipper. They are typically 10 to 12 inches long but can extend up to 36 inches in length.”
Damage to tire that has not lost air
The large amount of flexing can occur when a tire is significantly underinflated. When one tire in a pair of duals loses air, it can mean the failure takes longer to become obvious. In the meantime, structural damage is being done to the tire that had not lost air but is now being asked to carry up to 100% more load than normal.
What makes this type of failure dangerous is that it is entirely possible for a number of steel body cords to have failed but the rubber in the sidewall has not ruptured at the now lower inflation pressure. If that has occurred and the RV owner happens to discover a tire with low pressure then decides to “fix” things by reinflating the low tire, the damaged tire may now rupture with explosive force when higher pressure air is introduced to the tire.
What happens when a tire explodes
If you wonder what can happen when a tire explodes, a simple Google search of “tire explosion” will return just too many results.
SAFETY video. This is “zipper” failure from running a steel body tire when flat. But it shows the forces involved. Example. Be warned. This is a disturbing video. The Example shows what can happen when a large tire lets go. The failure of a wheel has similar forces.
If you are lucky, you will only blow your fender off when it lets go.
This post applies to any tire with steel body cords. Read the material list on your tire sidewall to learn what you have.
Roger Marble
*****
If you have tire questions, check out Roger’s Blog as well as his posts on RVtravel.com. There are hundreds of posts covering everything to do with tires.
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While in the Army I was on TDY to a remote base in Germany and some of us were on schiezen detail to the motor pool to mount tires for trucks. A friend was sitting on a tire while airing it up…I know……bad deal…anyway the tire blew up and he was pushed up almost to the ceiling of the shop. He was lucky…the split ring on the wheel was facing down. Situational awareness can save your six.
Wow Roger. This is an excellent video which every tire shop employee should watch – should be mandatory! Great info for us as well. “A picture is worth a thousand words”. Thanks for posting!
Thank you for this warning.
Thank you, Roger, for sharing the two videos! My goodness, those were graphic and unforgettable videos. You certainly have convinced me to never run an under-inflated tire. Thank you for your relentless campaign to inform. Have a great week and safe travels!