Are Our Tires REALLY that sensitive?

Bikeboy57 wrote:
Good Morning.

I am a certified engineer, although not a tire engineer. My career was in the manufacture of medical devices where safety is of paramount concern. The load inflation tables were generated by hours of testing by lab rat engineers where the design of the tire was verified to meet safety requirements. What that means is that the tire was tested at the load, inflation, and speed listed in the inflation table and met or exceeded the requirements. If you ask the engineer what would happen if you deviate from the load inflation, you will get two answers. One, sponsored by the company attorneys and the prudent answer, is I don't have any data to predict what will happen sir. The second off the record answer is likely to be, higher inflation pressures over what is recommended in the table do not degrade safety, and inflation pressures below recommended for the load degrade safety performance in proportion to how much lower than recommended the tire is inflated. That being said, ambient air temperature, driving speed, road surface, age of tire, and history of tire all factor in to it's safety. No one can generate a accurate predictor using all those factors of what a tire may or may not do.

Given the high consequences of a blow out on a truck tire, the easy no worries approach is inflate them to the max pressure on the sidewall, weigh the coach to ensure it doesn't exceed the load rating, and replace them every five years.

However, higher than needed inflation pressures make the coach ride rougher and handle less than ideal. Replacement intervals can very widely. A tire could have less than a 100 miles but have been setting in the full Florida sun on wet sand when compared to a five year old tire with 50,000 miles that had been driven weekly. If there are no cracks in the high mileage tire, it may be more safe than the one that has not been driven. Moisture is the enemy of the steel belts. UV light is the enemy of the rubber. Driving the tire and getting it up to temperature dissipates the moisture, and causes UV protectants to bloom to the surface of the tire.

By far the biggest danger is running an underinflated tire for the load. In order to prevent that, one should know the load and the minimum inflation, plus check it periodically. Some invest in pressure monitoring systems to help them. Some use a tire gauge.

I add a third safety measure, and I see from your other posts you have invested in an IR thermometer. At each stop, I walk the coach and toad checking tire temperatures with my hand. I am looking for a tire that is hotter than the rest which would be one's early indication of underinflation.

No, they are not made of crystal. And the world does not come to an end if you are off a few psi one way or the other. Besides, it would be comical to test an array of tire gauges at the pressures we run to see how they compare to each other.

Sorry for the long discourse.