How Broken Glass in the Road Affects Tires
Question: I often see people swerving sharply to avoid broken glass in the road. I wonder whether broken glass can really cause a tire to go flat? Is it worth the bother to avoid glass?--B.M.
Answer: Very seldom, if ever, can broken glass puncture a steel-belted radial tire or cause a blowout, but certain kinds of broken glass can damage a tire and cause it to fail prematurely.
Steel-belted radial tires have been a blessing for all motorists, not only because they have vastly improved the mileage between tire replacements, but also because they are tremendously resistant to punctures and leaks.
Experts estimate that steel-belted radials are 75% less likely to experience a flat or blowout than older radial ply tires.
Nonetheless, if glass is very sharp, it can cut into the rubber tread of the tire. If it penetrates to the steel belt, it can cause a wound that will allow dirt and moisture to accumulate.
Eventually, corrosion and contamination will cause the belt to separate from the tread, ruining the tire. This can occur anywhere from 5,000 to 15,000 miles later, long after you ran over the glass.
The most common glass in the roadway is from broken headlights and windshields at accident sites. The glass often shatters, throwing off tiny square blocks of glass. This tends not to be a great hazard to tires, because the glass has few sharp edges. The much greater threat to car tires is from broken bottles in parking lots, which can have long, sharp spikes that penetrate rubber easily.
The likelihood of damaging a tire is actually greater in summer when the pavement is hot. As rubber heats up, it becomes softer and more vulnerable to damage by foreign objects.
Q: I have been using 10W-40 oil in my car, because it is often on sale. But I wonder if I get adequate lubrication at the 10W viscosity. Maybe in warmer climates or in summer the weight is too thin. Would it be better to use 20W-40 in these cases?--D.H.F.
A: The majority of engine wear occurs in the first few seconds of starting a car, particularly when it is cold. To curtail engine wear, it is important for oil to begin flowing as quickly as possible. Thicker oil resists moving through the tiny passages in an engine until it reaches a higher pressure or temperature than thinner oil.
Most car manufacturers are now recommending that motorists use what historically has been very lightweight oil, such as 5W-30. You probably don’t want to use an oil thinner recommended by your owner’s manual, but you can safely use the thinnest oil it suggests. The newest top-rated oil, which is designated SG by the American Petroleum Institute, contains a richer additive package than older oils and provides all the lubrication necessary at lower viscosities.
Q: In this day and age, why can’t auto manufacturers design an instant car heater?--G.D.
A: Car heaters use hot engine coolant to warm a car’s interior, but the engine must be fairly hot for the system to work. The new smaller engines actually heat up more quickly than V-8s of the past.
The only other heat source for a car would be electrical energy, but that would require far more current than most automobile generating systems can produce.
An electrical heating system is possible, but the cost in weight, fuel economy and hardware would be so severe that few motorists would want to pay for. Some luxury cars have had electrically heated seats, but for general heating, almost all cars use excess engine heat.
