The Catastrophic Consequences of Tread Separation Failures

Tread separation occurs when the outer tread and belt package begin to detach from the tire casing. It is different from ordinary tread wear. A worn tire gradually loses tread depth. A separating tire can appear usable until the internal bond between tire components fails, allowing tread or belt material to peel away during operation. Federal tire standards define tread separation as “pulling away of the tread from the tire carcass,” which makes the term a structural failure description rather than a general label for bald tires or road debris.^¹

The risk is highest when the failure occurs at highway speed. A separated tread can strike other vehicles, damage the tire well or bodywork, destabilize the vehicle, or trigger sudden air loss if the separation ruptures the casing. NHTSA's tire crash research explains that tire problems in the pre-crash phase can include blowouts, flat tires, tread separation, and tire degradation, and that tire-related problems can contribute to loss of control and rollover.^²

Tread separation does not always happen the same way. In some crashes, the tire loses air suddenly and the vehicle becomes difficult to control. In others, the tread separates while the tire carcass remains inflated. NTSB's Lake City, Florida crash brief described a 15-passenger van whose left rear tire sustained complete tread separation while the carcass remained inflated. The van rotated, left the roadway, and rolled over.^³

A truck tire failure should not be described simply as a blowout unless the evidence shows rapid air loss. That distinction matters in commercial trucking investigations. Investigators need the tire carcass, tread pieces, belt fragments, rim evidence, and scene photographs to determine whether the tire lost air first, separated first, struck road debris, failed from age or heat, or came apart because of a manufacturing or retreading defect.

Heat, Underinflation, Age & Damage Can Start the Separation

Tires are built in layers. The tread is bonded to belt and casing components that must remain attached while the tire flexes under load. Heat, oxygen, underinflation, overloading, prior impact damage, aging, and poor repairs can weaken those bonds. Once internal cracking begins near the belt edge or tread shoulder, the failure can grow over time before becoming visible.

NHTSA's crash research found that underinflation, low tread depth, and prior tire damage were associated with tire problems in the pre-crash phase. Tires underinflated by more than 25 percent were overrepresented among vehicles experiencing tire problems, and vehicles with tire tread depth from 0 to 4/32 inch experienced tire problems more often than expected.^⁴ Aging is another mechanism. NHTSA tire-aging materials describe tire aging as a reduction or loss of material properties over time that can compromise structural integrity. Heat and oxygen are central to that process because they contribute to rubber degradation.^⁵

The Wawayanda, New York motorcoach crash provides a modern commercial-vehicle example. NTSB found that the left steer-axle tire failed catastrophically after tread and belt detachment and casing rupture. The tire showed evidence of prolonged underinflated operation, previous impact damage, and preexisting internal belt separation. Although the tires had legal tread depth, the failed tire contained internal damage that visual tread measurement alone would not reveal.^⁶

The Wawayanda report is important because it demonstrates why tread separation investigations cannot stop at tread depth. The failed tire had evidence including:

Wawayanda Motorcoach Tire

Evidence Found in the Failed Tire

Compression grooves

Bead heel deformation

Chafing

Heat-related discoloration

Radial splits

Belt-separation features

Those details allowed investigators to reconstruct a failure process that existed before the final roadway departure.^⁷

Federal Rules Address Visible Separation, Tread Depth & Tire Construction

Federal commercial-vehicle rules prohibit some tire conditions before they cause crashes.

Under 49 C.F.R. § 393.75, a commercial motor vehicle may not operate on tires with:

49 C.F.R. § 393.75

Prohibited Tire Conditions

Exposed ply or belt material

Tread or sidewall separation

Flat or leaking conditions

Cuts exposing ply or belt material

The rule also requires at least 4/32 inch tread depth on front tires of trucks, truck tractors, and buses, and at least 2/32 inch on other tires.^⁸ The same regulation limits the use of regrooved, recapped, or retreaded tires in certain front-wheel positions. That matters because steer-axle tire failures are especially dangerous. When a steer tire fails, the driver may have only seconds to respond before the vehicle leaves its lane.^⁹

Federal tire manufacturing standards also matter. FMVSS No. 119 currently applies to new pneumatic tires for motor vehicles with a gross vehicle weight rating of more than 10,000 pounds, along with specialty tires and motorcycle tires; light-vehicle tires at or below that weight are instead governed by FMVSS No. 139. FMVSS No. 119 includes performance and marking requirements and defines tread separation.^¹⁰

Retreads require careful wording. FMVSS No. 117 applies to retreaded pneumatic passenger-car tires. NHTSA has explained in an interpretation letter that retreaded tires for vehicles other than passenger cars are not covered by a comparable federal motor vehicle safety standard, although tire identification and recordkeeping rules may still apply.^¹¹ That regulatory gap does not mean commercial retreads are automatically unsafe, and it does not mean retreaders are beyond accountability. It means a retread failure investigation often depends on casing inspection, repair history, age, load, service application, retread process evidence, industry practices, and expert analysis rather than a single federal retread performance standard for heavy vehicles.

How Firestone Reshaped Tire Safety Oversight

The Ford and Firestone controversy remains the most important modern tire-separation episode in American safety regulation. NHTSA's Firestone investigation examined tread separations involving certain Firestone ATX, ATX II, and Wilderness AT tires. NHTSA reported that the failures generally began as belt-edge separations and that the subject tires were associated with crashes, injuries, and deaths.^¹²

The Congressional Research Service described the Firestone recall as a turning point for tire safety regulation and enforcement. CRS explained that the controversy focused attention on NHTSA's tire safety standards, defect investigations, civil penalties, and implementation of the Transportation Recall Enhancement, Accountability, and Documentation Act.^¹³ The TREAD Act was a direct legislative response to perceived failures in the defect reporting system. President Clinton's signing statement said the Act addressed shortcomings in identifying the Firestone tire problem and noted that some deaths and injuries might have been prevented if manufacturers and suppliers had given the government more timely information about potential defects.^¹⁴

The Department of Transportation Office of Inspector General later explained that NHTSA's TREAD Act implementation included early warning reporting requirements. Those rules were designed to give NHTSA access to manufacturer data such as deaths, injuries, property damage claims, warranty claims, consumer complaints, and field reports related to possible defects.^¹⁵

The Firestone history matters because tread separations are often pattern cases. One crash may look like an isolated failure. But warranty claims, field reports, prior lawsuits, internal testing, recall data, and complaint records may show whether the same tire model had a recurring separation problem. Tire defects often become clear only when scattered reports are gathered and compared.

Modern Recall Files Show the Same Pattern

The Goodyear G159 recall shows how tire-separation issues continued long after Firestone. In 2022, NHTSA announced that Goodyear would recall more than 170,000 G159 tires produced from 1996 to 2003 and sold for use on trucks and recreational vehicles. NHTSA said it opened the investigation based on claim and complaint data obtained through private litigation alleging tire failures that caused deaths or personal injuries.^¹⁶

Goodyear G159 Recall

170,000+ Tires recalled

1996 to 2003 Production years

2022 Recall announced

The Part 573 recall report for the Goodyear G159 stated that NHTSA opened a preliminary evaluation after receiving information from a private litigant alleging that the 275/70R22.5 G159 tire contained safety-related defects. The report discussed tread separations and other failures when tires were exposed to conditions including overloading and underinflation in the motorhome market.^¹⁷ NHTSA's PE17-009 investigation file is especially useful for heat and failure mechanics. It includes discussion of Goodyear engineering materials and testimony about elevated temperature, structural deterioration, and tread separation performance in heavy-duty tires.^¹⁸

The Associated Press later reported that a federal grand jury investigated Goodyear RV tires after NHTSA blamed the tires for crashes causing eight deaths and dozens of injuries. The AP also reported that documents from private litigation helped trigger the 2017 NHTSA investigation that led to the recall.^¹⁹ That history is important for trucking and commercial tire cases because it shows how litigation evidence can become public safety evidence. A separated tread on one vehicle may be a product of underinflation or road damage. Repeated similar separations across the same model, size, application, and service environment may point toward design, manufacturing, warning, or recall issues.

Crash Reports Show How Separation Becomes Loss of Control

NTSB's tire safety special investigation report provides several examples of tire failure leading to fatal crash sequences. In the Centerville, Louisiana crash, an SUV's left rear tire experienced tread separation and sudden air loss before the vehicle crossed the median and struck a school bus.^²⁰ In Lake City, Florida, the left rear tire on a 15-passenger van sustained complete tread separation while the tire carcass remained inflated. The van rotated, left the roadway, rolled over, and occupants were ejected.^²¹

NTSB's 2003 safety recommendation letter on 15-passenger vans also discussed crashes where rear tires experienced tread separation and blowout at highway speeds, followed by rollovers and ejections. The recommendations addressed tire pressure monitoring, training, and tire-related rollover risks.^²² NTSB's broader tire safety report identified multiple recurring concerns, including tire registration and recall problems, tire aging, poor maintenance practices, and barriers to technologies that could prevent or mitigate tire-related crashes. Across the tire-related crash investigations discussed in the report, 12 people died and 42 were injured.^²³

NTSB Tire Safety Report

People died

People injured

Across the tire-related crash investigations discussed in NTSB's special investigation report

Although several of these reports involve passenger vehicles or vans rather than tractor-trailers, the investigative lessons apply to commercial trucking. A tread separation can initiate a lane departure, cause a driver to overcorrect, damage vehicle systems, or create hazards for surrounding vehicles. In heavy commercial vehicles, the consequences may extend beyond the failing tire because of vehicle mass, cargo, roadway speed, and the difficulty of regaining control.

Preserving Tire Evidence Determines What Can Be Proven

The failed tire is the central evidence in a tread separation case. Investigators need the:

Tire Evidence Preserved for Investigation

Carcass Detached tread pieces Belt fragments Bead area Inner liner Sidewalls Punctures Repairs DOT tire identification number Companion tires Wheel Rim Vehicle damage

Each item can help distinguish a manufacturing defect from underinflation, overload, aging, improper retreading, road hazard damage, improper repair, or collision damage.

The Supreme Court's decision in Kumho Tire Co. v. Carmichael shows why expert methodology matters. The case involved a tire blowout and rollover in which the plaintiffs alleged a tire defect. The Court held that trial judges must evaluate the reliability of technical expert testimony, not only scientific testimony. Tire-failure opinions therefore depend on reliable inspection methods, not merely conclusions drawn from the fact that a tire failed.^²⁴

Texas litigation reflects the same causation problem. In Hathcock v. Hankook Tire, the court discussed competing expert theories about whether the tire failure resulted from a manufacturing defect or underinflation, including disputes over tread depth, wear patterns, and whether the observed separation was consistent with the plaintiffs' theory.^²⁵

That is why preservation is not a technical footnote. If the separated tread is discarded, the carcass is repaired, the wheel is reused, companion tires are replaced, or the vehicle is destroyed, the investigation may lose the only evidence capable of distinguishing defect from misuse or crash damage. Tire cases often turn on small physical details such as oxidation at crack surfaces, belt-edge appearance, inner-liner damage, repair history, bead marks, rim-flange evidence, and whether the separation began before or during the collision.

Tread separation failures can involve product manufacturers, retreaders, carriers, maintenance vendors, tire dealers, and drivers:

Who May Be Responsible

Manufacturer May be responsible for a defective design or manufacturing process.

Retreader May be responsible for using a damaged casing or improper bonding process.

Carrier May be responsible for operating aged, underinflated, overloaded, or visibly damaged tires.

Service shop May be responsible for improper repair or installation.

The evidence determines which theory fits. A tread separation may unfold in seconds on the highway, but the failure often begins much earlier. It may begin with heat, age, pressure loss, casing damage, retread errors, or a defect known through complaints and warranty claims. The tire itself is the record of that history. Once it is gone, the most important witness to the failure is gone with it.

Tread Separation Failures