Special Trailer (ST) tires have a maximum speed rating of 65 mph,* and if exceeded or if the tires are under-inflated, the tire temperatures increase, causing a weakening of the tire structure, which can lead to a shortening of the life expectancy of the tire and/or a catastrophic accident.* We have learned the importance of continuously monitoring the tire pressures (and our speed) from preflight to our arrival and midway during our stay and during our return trip home. To facilitate this, we have relied on a tire pressure monitoring system (TPMS) since 2008, first with Doran, and then with PressurePro since 2011 (See “TPMS-Update“)
Typically, two or three days before departure, I install the sensors on the tires and adjust the tire pressure to be as close as possible to the specified maximum 50 PSI cold for our ST 215/75R14 Goodyear Marathon tires for the expected temperature at the time of departure. (Our tow vehicle’s truck tires also get the sensors and have a cold PSI of 60 for front and 75 for rear tires.)
I keep a running log of the pressures and temperatures for each trip, which is started at the beginning of our trailer trip prep week and detailed in my post “Airstream Safari trip notes.”
On the left is the log for our December trip. The sensors were installed on Thursday and I noticed that the street-side rear sensor pressure reading was lower than the other sensors, which may indicate a slow tire or sensor leak. I added air to this tire on the following day. Early Saturday morning, the outside air temperature was 40°, and I noticed that the rear curbside sensor was not transmitting a pressure reading until it warmed up to 50°. We departed Sunday afternoon and when we arrived at our campsite, I discovered a 1″ washer head machine screw embedded in our rear curbside tire as I was covering it for the night. The next day, our PressurePro monitor confirmed my fear that the screw had penetrated the inner tire. I replaced this tire with the spare and documented this in my post, “A Marathon tire repair.”
Washer head machine screws, commonly used on automobiles and motorcycles, are often encountered on highways and back roads, and I suspect that the washer head, when run over, causes the opposite end to rise towards the tire and puncture it straight on.
We find the most screws and nails in campgrounds, often brought in with firewood by campers, as seen in my post, “Nailing it… A TPMS encore.”
This camping season, our PressurePro TPMS sensors became 5 years old and were showing their age. As seen in the log above, one was not transmitting a pressure reading in the early morning cold and another was very slowly leaking air, confirmed by temporarily putting another sensor in its place. I contacted PressurePro and they sent me 4 new sensors for my trailer at a discounted rate, along with a Sensor Seal/Installation Tool Kit, that I will use to upgrade the truck’s sensors.
An obvious improvement in the new sensors is that each sensor has a unique green identification number displayed on its side, which decreases the chances of placing a sensor on the wrong location. (Each sensor is programmed for each tire location and I place each sensor in a zip lock bag assigned for each tire location when not in use, thus prolonging the battery life. See how to set up the PressurePro tire pressure monitoring system in the video, “Protect Your RV with a TPMS“*)
A less obvious, but more important improvement is that the new PressurePro sensors now have a new Sensor Seal, a two-piece valve system that uses a hard plastic depressor to more fully depress the valve and yet, provides a hard stop during installation, protecting the seal. (Older sensors were often over tightened, resulting in damage to the O-ring seal.) Older sensors with the one-piece seal can be upgraded by using PressurePro’s Sensor Seal/Installation Tool Kit that contains 10 sensor seals and a seal installation tool.
A tire pressure monitoring system adds to our peace of mind while on our safaris, where we’d rather come face to face with a coyote than with tire trouble! (See Author’s update below regarding high temperature alerts and other PressurePro improvements.)
*This is a link to a YouTube video.