What is a zipper?

Kevin Rohlwing, TIA Senior Vice President of Training: “A zipper rupture is a spontaneous, explosive burst of compressed air that occurs in the sidewall flex area of steel cord radial truck tires. It usually follows the circumference of the tire and can range anywhere from 12 inches to over 3 feet in length.”

How dangerous is it?

“It can seriously or fatally injure if the proper procedures are not exactly followed.

“Zipper ruptures don’t care how long you’ve been in this business or how much experience you have. Sometimes the signs of a potential rupture will be apparent and sometimes they won’t.

“The problem with zipper ruptures is the unpredictability associated with ‘fatigued’ or damaged sidewall cables.”

How can we identify a potential zipper?

“The key is to thoroughly inspect both sidewalls prior to inflation. Any undulations or bumps could be a sign.

“If the tire was suspected to have been run at 80 percent or less of normal operating inflation pressure or was overloaded, it must be completely deflated, demounted and inspected.

“Like any machine, if a tire is worked too hard for too long, it’s going to break down. Once the assembly reaches less than 80 percent of the recommended inflation pressure, the tire is forced to flex more and generate a lot of heat.

“The best thing to do is to treat every tire – even new ones – as if it were a potential zipper.

“Start by following Occupational Safety and Health Administration (OSHA) regulations. Mount the tire on the rim and inflate to approximately 5 psi to seat the beads. Now move it to the restaining device, remove the valve core and connect the clip-on air chuck.

“Inflate the tire to 20 psi. If it’s a bus or refuse tire, inflate to 40 psi.

“Now inspect the sidewalls for undulations or distortions. But do so from a safe distance; remain outside the trajectory. Don’t place your hands inside the safety cage while inspecting the tire. And keep your head away from the tire and cage.

“Now turn off the radio and listen.

“A telltale sign of a zipper rupture is the ‘popping’ noise steel cords make as they break.”

Does it sound like popcorn popping?

“It does. Just before the zipper erupts, you may hear crackling, snapping and popping.”

What’s next?

“Inflate to 20 psi over the maximum inflation pressure, which you’ll find on the sidewall. As you’re doing so, continue to listen for popping and look for bulges. Most zipper ruptures occur between 20 and 120 psi.”

Is this new?

“It is. TIA, Technology & Maintenance Council and Rubber Manufacturers Association have carefully studied this procedure after mounting and inflating over 300 tires judged to be suspect. The former procedure said to inflate 20 psi over target pressure. Now, the recommendation is 20 psi over maximum pressure, not to exceed 120 psi.”

Still wait 20 minutes?

“No. The new procedure requires that you listen for snapping and crackling, but if you hear or see nothing suspicious, you may lower the inflation to your target psi immediately, rather than hold pressure for 20 minutes.”

Tell us about the video.

“Some people tend not to read as carefully as they grew up in the ‘MTV generation.’ Inflating a truck tire to 100 psi is an inherently dangerous procedure that should never be taken lightly. Many of the safety procedures we have are in direct response to serious and fatal accidents. With something as vitally important as tire safety, the TIA found the best training programs provide both video and written instruction.

“We worked hard to update TIA’s Commercial Tire Service and Fleet Truck training programs. The updated zipper video is just one portion of the entire training program available for tire technicians.”

How do you sign up for training?

“Visit our Web site at www.tireindustry.org and click on training and education. OSHA requires all people working on tires – whether they work in a tire dealership or fleet facility – to receive safety training.

“And remember: “Just because a zipper rupture hasn’t happened to you doesn’t mean it won’t, so don’t take the chance. Look for the signs, listen for the sounds, and your chances of getting injured by a zipper rupture are greatly reduced.”