Maintenance & Care

Tire Pressure

Optimum Performance Begins with Proper Tire Pressure.

The inflation pressure in all tires, including the spare tire and inside duals, should be checked with an accurate tire gauge when the tires are cold on a frequent basis, such as daily during continual service as required by the Department of Transportation. This includes vehicles with a Tire Pressure Monitoring System (TPMS). Do not reduce pressure when tires are hot from driving. Any tire that continually requires reinflation is a serious safety risk. Use metal valve caps on each tire to ensure a complete air seal during operation and to keep out dirt and moisture.

Do not exceed the inflation pressure on the tire sidewall. Manufacturers of trucks and buses identify tire inflation pressure for each axle on the vehicle tire placard, certification label, or in the service manual. This pressure is always sufficient to carry the maximum axle load but may not deliver optimal tire performance.

Tires perform best when inflated to match vehicle and axle loads. Steer tires often require maximum inflation pressure to carry the steer axle load while drive and trailer axle tires should be set at pressure corresponding to actual tire loading. To help keep your tires properly inflated, refer to the Yokohama Tire Pressure Inflation Calculator at

Check out this short video with tips on how and when to check air pressure to improve your fuel efficiency, protect your tire investment, and maximize safety on the road.

Driving on tires with improper inflation is dangerous.

  • Underinflation causes excessive heat buildup and internal structural damage.
  • Overinflation makes it more likely for tires to be cut, punctured or broken by sudden impact.

These situations can cause a tire failure, including a tread/belt separation, even at a later date, which can lead to an accident and serious personal injury or death. Any truck tire known or suspected to have run at 80% or less of normal operating inflation pressure could possibly have permanent structural damage and should be considered a flat tire.

Understanding Differences in Tire Inflation

Proper performance requires proper inflation. Under- or overinflated tires can negatively impact tire life and traction.


Underinflated tires can’t maintain their shape and become flatter, causing over-deflection, internal heat build-up, increased rolling resistance and reduced fuel economy.

  • 20% underinflation can reduce tire life 30%
  • 30% underinflation can reduce tire life 40%
  • 40% underinflation can reduce tire life 50%

Zipper Ruptures in Steel Cord Radial Truck & Bus Tires

  • Any steel cord radial truck & bus tire operating underinflated and/or overloaded must be approached with caution. Permanent damage due to operating the tire underinflated and/or overloaded cannot always be detected, although the tire could have permanent sidewall structural damage (steel cord fatigue).
  • Ply cords weakened by underinflation and/or overloading may break one after another, until a rupture occurs in the upper sidewall with accompanying instantaneous air loss and explosive force. This can result in serious injury or death.
  • For inspection procedures, see USTMA’s TISB, Vol. 33 No. 5;

Proper Inflation

Proper inflation is critical for the performance of your tires. When a tire is inflated properly, it’s load is equal on all ribs or elements, giving a square footprint shape.

Proper Inflation


Overinflated tires tend to have a short shoulder rib contact area, causing scrubbing action, uneven wearing of the shoulder rib and placing more strain on the contact area.



Property damage, serious personal injury or death may result from tire failure due to underinflation, overinflation, or overloading – Always follow vehicle owner’s manual, vehicle tire placard or certification label.

Inflating an unsecured tire is dangerous, as it could burst with explosive force resulting in serious personal injury or death.

  • Never adjust the inflation pressure of a truck tire unless it is placed in a safety cage, or is secured to a vehicle or a tire mounting machine.
  • Never stand or lean over the tire or in front of the valve when inflating.
  • Never reinflate a truck tire that has been run at very low inflation pressure (i.e. 80% or less of normal operating pressure) without a complete inspection of the entire tire by a qualified tire service professional, including interior and exterior. See OSHA Demounting and Mounting Procedures at