Why Do Tires Fail?

Tires are undoubtedly the most critical safety component on a vehicle. Where the rubber meets the road affects traction, handling, steering, stability and braking. Because of this, a sudden tire failure can have serious consequences, especially if it occurs at highway speeds in a vehicle with a high center of gravity.

It’s amazing that tires hold up as well as they do considering their vulnerability to road hazards. Many tires today are easily capable of going 80,000 miles or more – provided they are properly installed, maintained, aligned and inspected regularly.

With proper care and normal use, most tires will go the distance without a problem. But sometimes tires fail. Maybe it’s the installers fault, the manufacturer’s fault, the motorist’s fault or nobody’s fault. Even if the failure rate is only one in a million tires, a trial lawyer will argue it’s one failure too many for his client.

The purpose of this column is not to assign blame for tire failures but to examine some of the causes and ways tire dealers can minimize the risk of such failures.

Failures From Underinflation
One of the most common causes of tire failure is underinflation. Tires that are underinflated experience excessive sidewall flexing, which causes them to run dangerously hot, especially at highway speeds during hot weather.

The buildup of heat can lead to tread separation or a sudden blowout. The underlying cause here may be lack of maintenance (not checking inflation pressure regularly) or a slow leak that has allowed the tire to lose air over time.

The main responsibility for preventing this type of failure is squarely on the shoulders of the vehicle owner. Motorists should read their owners manuals or the tire inflation decal on the door jamb or glove box door and know how much pressure their tires require. They should own a tire pressure gauge and know how to use it. They should check inflation pressures when the tires are cold and add air as needed to maintain the recommended pressure. If a tire is losing air, they should take their vehicle to a tire dealer so the problem can be diagnosed and repaired. Punctures, rim leaks and leaky valves can all cause a tire to lose air pressure.

The tire dealer’s responsibility is to educate their customers on the importance of maintaining proper tire inflation pressure. If a customer doesn’t know how to check their tires, show them. And if they don’t own an accurately calibrated tire gauge, sell them one when they purchase tires or have tires repaired.

Technicians can also do their customers a service by checking tire inflation pressures anytime a vehicle is in for service, be it a tire rotation, alignment, brake job or oil change. Self-service gas means nobody may be checking the tires if the motorist doesn’t do it himself.

Failures From Overinflation
Overinflating tires increases ride harshness and may increase a tire’s vulnerability to damage caused by potholes and curbs. Overinflation occurs when somebody adds air to a tire until it "looks full" or doesn’t use an accurate tire gauge. Never exceed the maximum pressure rating on the side of the tire. Always follow the vehicle manufacturer’s recommended inflation pressure for vehicle load and operating conditions (provided the tire size and load rating hasn’t changed from what was OE).

Failures From Overloading
Overloading a vehicle, or driving on tires that do not meet the load rating requirements for the application, is asking for trouble. This is more of an issue with pickup trucks, vans and SUVs than it is passenger cars, especially those that may be used as utility vehicles to haul building materials or other unusually heavy loads.

The best way to prevent this kind of failure is to check the load rating of the tires and make sure they match the application. If they don’t, recommend upgrading to a tire with a higher load rating. The customer is still going to make a buying decision, but make sure they do so with a complete understanding of the consequences.

Failures From Road Hazards
Most motorists will try to avoid really bad potholes, debris on the road and curbs. But sometimes these hazards are unavoidable and cut, puncture or damage a tire. If the damage does not cause the tire to go immediately flat, it may weaken the tire and cause it to fail later or under high speed/load/temperature conditions.

Ultra-low profile tires are especially vulnerable to sidewall damage when hitting curbs or potholes because of the narrow sidewall height.

The only way to prevent this kind of failure risk is to avoid driving altogether. Since that isn’t practical, the next best thing is to steer around road hazards whenever possible, and to inspect the tires for possible damage if the vehicle ran over something really nasty.

Technicians should make it a point to inspect the tires and wheels for possible damage anytime a vehicle is in for service. If a tire has gone flat or was punctured, it should be removed from the wheel and carefully inspected inside and out for damage. If too damaged for a safe repair, the tire is unsafe and must be replaced. If the wheel is cracked or bent, it should be replaced.

Failures From Structural Defects
Here’s the category trial lawyers love best because it often means huge settlements when defects can be proven. Manufacturing defects that result in poor adhesion between the tread and belts can result in tread separation and blowouts. Fortunately, in real life, such defects are rare and the cost of the tire is usually covered under warranty.

This risk can be reduced by inspecting new tires when they are first installed for obvious defects such as bulges, lumps, cracks, excessive runout, etc. Tires should also be inspected for defects or damage anytime a vehicle is in for service. Any tire that is bulging, cracked, has missing chunks of rubber or similar problems is unsafe and should be replaced immediately.

Technicians should be warned that puncture repairs that do not plug the hole may allow moisture to penetrate the tread and reach the steel belts. This can lead to rusting and increase the risk of tread separation and tire failure.

Failures From Excessive Speed
Driving at sustained high speed on tires that are not speed rated or are badly worn is just plain stupid, especially during hot weather or with an overloaded vehicle. Speed-rated tires have additional reinforcements and are better able to dissipate heat than standard tires.

Make sure the speed rating on the tires matches the vehicle requirements and owner’s driving habits. If they don’t, recommend upgrading to an appropriate speed-rated tire.

Failures From Installation
Tires can be damaged if they are not mounted properly, especially high performance tires on custom wheels.

Not using a bead lubricant when mounting a tire, or stretching or tearing the bead because the tire was not correctly positioned on the wheel, can cause bead damage that may allow a leak air or bead failure later on.

Overinflating a tire in an attempt to seat it, or failing to fully seat the tire, can also lead to problems. We’ve all heard of instances where unknowing techs have tried to mount a tire on the wrong sized rim (watch out for 16.5- and 15.5-inch rims).

The best way to avoid these kinds of mistakes is to make sure you know how to use your tire mounting equipment, that the equipment is in good condition, and that you know how to handle various sized tire and wheel combinations without damaging either. Technician education, training and attention to detail are all musts to prevent this kind of failure.