Proper tire inflation is one of the most important tire maintenance tips that will bring you stability. It’s one of the most talked-about tire issues all over the world. This is because it’s a universal constant that is worth attention and time. According to Jason Miller, National Fleet Channel Sales Manager at Cooper Tire and Rubber Co., it’s the air in the tire that carries the load, not the tire itself.
He goes on to add that the two most important tire attributes are the shape of the contact patch and how it manages flexing. Take, for example, a truck carrying 60,000 pounds down the highway. At 60 70 MPH, the tires shouldn’t flex too much because this could raise temperatures and cause failure. In addition, you want as much of the tire’s width to be in contact with the ground. This ensures the truck is well-positioned for starting, turning, and stopping.
This requires you to maintain the proper PSI. While the PSI varies with the loaded weight, there are a few places you can start.
Miller says that it’s more important to ensure that the PSI set is able to handle the load present rather than having it at a set number. The steer axle is the most consistently-loaded tire on the truck because of the engine. For example, an 80,000-pound setup will have 34,000 pounds on the trailer tires, 34,000 pounds on the drive tires, and 12,000 pounds on the steer.
A 12,000-pound setup on the steer axle will have 6,000 pounds per steer tire and 34,000 pounds spread over eight drive tires. This reduces to 4,250 pounds per tire. You’ll need the full 110 PSI in a typical steer tire and more if you have more weight on the steer axle. You will, however, need less than that on the drive tires.
For maximum tire effectiveness, you start by finding the right number for your load. Steer tires should be set between 100 and 110 PSI while fully loaded drive tires should be set between 85 and 90 PSI.
Many tire makers have inflation load tables that can guide you when determining the proper tire pressure. According to B2B regional technical partner and customer engineering support manager at Michelin North America Inc., Lawrence Williamson, it’s important to use these tables unless otherwise directly advised by your tire manufacturer.
You can select the proper load and inflation table by picking your tire size and matching the sidewall markings to the table with the same dimensions. If you have 275/80R22.5 LRG X line Energy D tires on the drive position, weight per axle increases from 18,760 pounds to 21,040 pounds. The best PSI here should be increased from 85 to 100 PSI.
You’ll need to set the tire pressure reading when the tires are cold. So, it’s important to take care of this before the truck leaves the yard. According to Matt Schnedler, the product manager for truck and bus radial, U.S. and Canada at Bridgestone Americas Tire Operations (BATO), the pressure is at its most accurate when tires are inflated while cold. This could be when the truck has been sitting for at least three hours or has been driven less than a mile at moderate speed.
Ensure Your Team can Maintain the Pressure
Once you set the right tire pressure at the yard, you need to ensure that the men and women that spend most of the time with the trucks are able to maintain the right tire pressure. They, therefore, need proper training.
Many drivers use thumpers to check tire pressure. While this is common, several tests have shown that it is not accurate. Pat Keating, senior manager of field engineering at Yokohama Tire, adds that fleet managers that train drivers to switch from thumpers to gauges see an increase in fleet pressure consistency. Many fleets achieve the best results when there is a system in place to integrate driver efforts with maintenance staff.
To keep proper pressure, it’s also advisable to invest in automatic tire inflation systems and tire pressure monitoring systems. You can start by ensuring that every driver has a reliable tire pressure gauge. For proper performance, you’ll need to ensure the air pressure gauge is checked against a master gauge that’s calibrated. The manager of filed engineering at Falken Commercial Division also recommends using flow-through valve caps to make it easier to check tire pressure.
After equipping your drivers with the right tools, the next important thing is to make sure they know how to use them and that they are doing tire inspections as required. It can sometimes be difficult to make pressure checks regularly due to hectic fleet schedules. In addition, in-route tire issues tend to raise maintenance costs. One way to ensure the pressure is being checked and maintained is to have a checklist with mark dates on it.
Michelin’s Williamson outlines three responsibilities for drivers when it comes to maintaining tire pressure.
- Doing walk-around inspections before the truck leaves on a trip as a preventative maintenance tip.
- Have knowledge of the recommended steer, drive, and trailer inflation pressure as well as the minimum fleet tread depth.
- Be aware of the effect “out of service” violation has on their CSA scores. Drivers have a responsibility to ensure the tractor-trailer is in good condition before it leaves.
Other recommendations include checking inflation pressures at least once a week on all tires and spares. This is of course while taking into account the effect temperature changes have on tire pressure. A drop in ambient temperature results in a drop in tire pressure. Consult your tire manufacturer’s user manual to know if you’ll need to make adjustments. Be careful, however, when temperatures drop below freezing point since ice can accumulate in the valve stem and cause leaks. You can check your tires in a heated facility if temperatures drop below the freezing point.
Williamson also adds that trip duration has no direct impact on tire pressure. It’s all about the PSI and load. Schnedler says that in addition to TPMS devices, fleet managers and drivers should still do a manual hands-on inspection to check for bulges, cuts, and cracks. Some of the questions to ask yourself include:
- Is the tread depth too low?
- Is there irregular wear?
- Are there punctures or nails?
- How old is the tire?
- Are the wheel hand holes in driver tires aligned?
- Do steer tires have the proper load ranges for the axle?
Remember to check the inside sidewalls of the duals as well. Yokohama’s Keating says that deep cuts can let in water that can cause damage to the casing. As you and your drivers get started on maintaining the correct tire pressure, ensure that you put in efforts to lay a solid tire pressure management foundation.