It's an important issue and often misunderstood, tire pressure. Another reason to read your truck and trailer owners manual. What allot of folks don't understand is what's printed in the truck owners manual, over-ride what is stamped on the side of the tire. The truck manufacture specifies to the tire company what they want in a factory tire sold with the truck when new. And the truck manufactures decides and takes responsibility for the load rating of the tire and tire pressure. So look in the owners manual and the safety compliance sticker in the drivers door frame to see what your trucks tire pressure should be. (Trucks according to the government also means SUV's and mini-vans, so when I say trucks, it covers the category.)
Are you confused yet? Some people inflate under the air pressure required on the safety compliance door sticker for a softer ride. But low tire pressure causes the tire sidewalls to flex more and build up heat. Not a good thing. I would say to stick to the air pressure ratings in the owners manual and safety compliance door sticker, that's what's been tested to be safe. Some manufactures have a different rating for the front truck tires and rear tires.
Get a good tire pressure gauge. These are the long ones sold at better auto parts stores and truck stops. Cheap short air pressure gauges are not accurate or not accurate for long. If your truck has a factory tire pressure monitoring system and has individual pressure readings, it's interesting to watch the pressure go up when the tires warm up. You can even tell air pressure difference from the sunny side of your truck and the shady side. That tells you that heat expands the tires to increase air pressure. This is why you want to check the air pressure cold, before you drive off.
Trailer tires are basically the same as truck tires when it comes to proper air pressure. Look at the trailer owners manual and compliance sticker near the trailer tongue. Trailer manufactures match tires like they do axles to be the proper combination for safety. With torsion axles that many trailer tires have now, a flat tire may not feel much different and it's not always safe towhip the trailer to look at the tires. So you could drive for miles with a flat and not know it until it destroys the tire and pieces are flying off the trailer or when a flat tire tears apart and takes the trailer fender with it.
Newer trucks have tire pressure monitors as standard equipment as mandated by law. There are aftermarket tire pressure monitor systems such as Pressure Pro that I use to keep track of tire and trailer pressure on the go. Another value of having an onboard tire pressure monitoring system is being alerted that you have lost a tire or tire and wheel, if you didn't see it roll past you. It happens more often than you think. Tires will naturally loose air over time making if important to check your tire pressure often. Nitrogen instead of air is gaining popularity with over the road semi-trucks. It leaks less than air, collects less water inside the tire and may make the tires last longer. It's used in most race cars.
On a 70 degree day leaving Los Vegas in November, blew a rear tire on my truck. Of course the spare was low. So I whipped out my Slime kit with the air pump. The smaller pumps work best with no weight on the tire, so you may have to jack up the trailer/truck, taking the weight off to air up. Slime works great on small holes, but you do have to let the air out of the tire, unscrew the valve stem, squeeze in the slime and then re-air the tire up. I'd suggest for the larger Slime pumps to use the 30 amp power point 12 volt plug in your truck or clamp directly to the battery not the 20 amp cigarette lighter as pumping up a larger tire will take over 15 minutes and cause heat.
Slime is also great for ATV tires, wheelbarrows, and I've used it on idler wheels on my hay swather. 2 ply tires are especially attracted to stickers and trailer tires could use Slime as a preventative tool.
Newer trucks have hub pilot wheels, which transfer weight to the hub. Most trailer wheels are stud pilot putting the weight on the studs. This is part of the reason lug nuts can loosen on your trailer, if you're lucky the loose lug nuts will make a racket bouncing around in the hub cab that you'll notice. On long trips it's good to check trailer lug nuts with a star wrench, which tells you to tighten the lug nuts in a star pattern. Get a torque wrench, mine cost $10. Your trailer/truck owners manual will tell you how much to torque the lug nuts. Aluminum wheels will contract and expand loosening the nuts more than steel wheels. While you are there, touch the wheel to see if it's over hot. Which could mean a dragging brake or wheel bearings going out. And keep on rolling.
Author H. Kent Sundling writes for AgWeb.com via a special agreement withMrTruck.com.