More on zipper ruptures I'm writing in answer to reader Mike Smith's request for information on the causes of zipper-type ruptures in all-steel reinforced radial truck tires. (See TB's June 21 issue.)
We experienced a zipper rupture in a repaired 10R22.5 Goodyear G186 drive tire that sustained a simple nail hole puncture in the center of its tread. The tire was used as an inside dual on a bus operated by our local school district.
The bus had been brought to the shop for U-joints and was up on the rack when the flat tire was discovered. In checking, we found that the remaining five tires on the bus had only 80 psi inflation pressure. The driver said the tire pressure had purposely been reduced to soften the vehicle's ride.
Jim Coon, an employee with our company almost 12 years, performed the repair and was in the process of airing up the tire. He was using a gauge with a six-foot lead and had just reached 85 psi when the tire zippered and blew. The explosion sounded like a cannon going off and moved the tire safety cage nine feet and crushed a nearby trash can before coming to a stop.
That tire (see photo), which showed no signs of having been run flat, was less than a year old, had been installed and balanced correctly and was the proper tire for the application.
I'm sure age and over-loading can contribute to a tire's zipper rupture. But the cause of failure in this case simply was underinflation.
Tires should be aired to whatever pressure is stated on the sidewall. The engineers who designed the tire should determine how much air pressure to put in it—not the vehicle's driver or the tire dealer.
West Side Inc.
Lake Eufaula, Okla.
4WD and All-WD tires
I'm a retired dealer and my son (Bill Bailey Jr. of Bill Bailey for Tires) passes Tire Business along to me so I can relive the glory days.
Your publication's July 5 issue covered in depth the drivetrain problems that can result from mismatching supposedly ``same-size'' tires on all-wheel- and four-wheel-drive vehicles.
Any retreader from the old days will recall that the ``one-size-fits-three-molds'' problem of that era was also a nightmare.
However, in those days we used a sales method that I believe should be revived as a partial answer to such problems.
We responded to customers wanting to replace only two tires by advising them to buy four and telling them we would purchase the remaining tread on their other two worn but still serviceable tires.
The sales pitch we used was that their car would look better, handle better and be safer having four matching tires. This approach really worked and also provided us with two used tires that later could be sold at a 100-percent profit.
``Buying the miles left on the customer's used tires'' can prevent problems resulting from having different-sized tires on the vehicle's front and rear axle and allow the dealer to make a new friend and turn a respectable profit at the same time.
Bill Bailey Sr.
Mount Vernon, Wash.