Are retreads the cause of rubber on the road? Those of us in the industry know that a properly retreaded tire will not fail simply because it is retreaded. And we understand their importance.
So, when a government agency or newspaper editorial or letter to the editor advocates legislation because “all those retreads on the side of the road are a danger to the driving public,” we write them off because the people behind the complaining are no doubt uninformed. Retreaded tires often fail for the same reasons that new tires fail: They are run underinflated, or were damaged by a road hazard, or were serviced improperly.
How do we know? Through experience and empirical research, the latter undertaken by transportation companies or organizations. At least that’s what we tell ourselves.
A new independent report commissioned by the National Highway Traffic Safety Administration (NHTSA), however, backs up our claims. At 214 pages, the “Commercial Medium Tire Debris Study” is a comprehensive analysis of what causes rubber on the road. It answers our initial question with a resounding “No.”
The study had multiple purposes, but two stand out: to investigate why medium and heavy truck tires fail, and determine the extent of failures for retreaded truck tires.
There have been at least five studies over the last 14 years that have touched on these objectives, but they have either been regional in scope or industry-based.
This one covered almost all the bases, starting with 86,000 pounds of tire debris and casings — the equivalent of more than 700 conventional medium truck tires. They were collected in the summer of 2007 across the country at designated stretches of highway and truck stops.
After weeding out any passenger and light truck debris and unusable samples, the authors were left with a more than representative amount of rubber on the road. The casings and debris were then analyzed to determine why they failed. The key failure categories were:
1. “Over-deflected operation,” which is primarily caused by under-inflation, overloading or a combination of the two. Tires were put in this category if the failure was related to flex.
2. Excessive heat.
3. Road hazard.
4. Maintenance/operational, which includes improper tire repair, excessive wear, damage in the mounting/demounting process and driver or vehicle operation.
5. Manufacturing/process issues.
6. Other (excessive intra-carcass pressurization). “Other” failures, which are often themselves caused by failures listed in the other categories, were minimal.
The results were as expected. In order, the top three reasons that the casings were taken out of service were road hazard damage, improper maintenance and under-inflation/overloading. They represented 76% of the failures.
The top three probable causes for failure of the fragments were road hazards, excessive heat and improper maintenance. They accounted for 83% of the failures.
When new tire casings and debris are compared to retreaded casings and debris, the failure rates are similar.
It seems like every segment of the industry was involved in the study. The authors were assisted by, among others, five state departments of transportation, Bridgestone Americas Inc., the Rubber Manufacturers Association, Smithers Scientific Services Inc., and the Tire Retread and Repair Information Bureau.
Two tire dealers also were involved: Belle Tire Distributors and Shrader Tire and Oil.
The only problem I had with the study was this statement: “The proportion of tire debris from retread tires and (new) tires is similar to the estimate proportion of retread and OE tires in service.”
Based on the percentage of new truck tires shipped and retreaded in the U.S. from 1998-2007, nearly 57% were new original equipment or replacement tires. Retreads represented 43.2%.
However, close to 68% of all the truck tire debris in the “Commercial Medium Tire Debris Study” was from retreads. Comparable results can be found in the other surveys.
Even if you take into account inconsistencies among retreaders across the country, and the predominance of retreads on trailers, the numbers still don’t match. Even if some of the OE tires are sitting on new trucks and trailers that aren’t selling, shipments over a 10-year period should factor that out.
But this minor discrepancy doesn’t change the findings of the study, which support the safety of retreaded tires, and discount the need for legislation. ■
