Michelin Tyres

Right Pressure

Right Pressure

Right Pressure

Under or Over Inflation

Under-inflation or over-inflation of your tyres can generate cost and danger. Tyre life, driving comfort, good traction and braking :

These performances can be influenced by inappropriate inflation pressure.

Under-inflation generates excessive flexing of the tyre casing which results in tyre overheating, increase of rolling resistance and premature wear. In extreme cases, under-inflation can cause tyre damages.

Likewise over-inflation can affect tyre life. This leads to reduced grip and irregular wear especially in drive axle fitment.

Michelin has carried out surveys to measure pressures of vehicles in actual operations. Two significant tendencies are observed : under-inflation at front axle vs over-inflation at drive axle.

Pressure of Inflation

Pressure of inflation

The inflation pressures of tyres for commercial vehicles must be adapted to the load, speed and conditions of use. Respecting the pressure of inflation is a prime factor in ensuring that the vehicle is safe when driving.

How do I determine the pressure of inflation?

The fully loaded vehicle must be weighed by axle. In the meantime, you should use the basic pressures in the MICHELIN table "Basic pressures for common conditions of use".

  • Over inflation is bad for comfort, grip, and the tyre's longevity
  • Insufficient pressure of inflation leads to an abnormal rise in the tyre's temperature, leading to irreversible deterioration of its inner parts. This may cause destruction of the tyre with a sudden blow-out.

The consequences of running with insufficient pressure of inflation are not necessary immediate and may even become apparent after correction. The pressure of inflation should be regularly checked "when cold" each time the vehicle returns to the garage using an accurate and regularly checked pressure gauge (according to the marker' recommendations). When operating in very cold temperatures, consult the Michelin Truck Bus Tyre Service Manual for correct inflation procedures. Additionally, altitude can have a slight effect on air pressure. For every 300 meters increase in altitude above sea level, air pressure will increaseapproximately 0.5 psi.

Important :

Don't forget the spare tyre.
Never deflate a tyre "when hot", just after running


Any inflated tyre mounted on a rim contains explosive energy. The use of damaged, mismatched or improperly assembled tyre/rim parts can cause the assembly to burst apart with explosive force. If you are struck by an exploding tyre, rim part or the air blast you can be seriously injured or killed.

Effects of Tyre Life

Inflation Pressure

The most critical factor in tyre maintenance is propoer inflation. No tyre or tube is completely impervious to loss of air pressure. To avoid the hazards of under inflation, lost-air must be replaced. Inflation pressure has a direct impact in tyre performance - both tread life and endurance - as shown in the following charts:

Influence on cost


Driving on any tyre that does not have the correct inflation pressure is dangerous and will cause tyre damage. Any under inflated tyre builds up excessive heat that may result in sudden tyre destruction. Pressures which are too high can lead to more rapid and uneven wear as well as being more vulnerable to road hazard damage. Consult a Michlein tyre dealer or Technical Data Book for the proper inflation pressures for your application.

Inflation instruction

With inflation cage

  • Follow the maker's instructions.
  • The cage must be placed in a fitting area and clear area.

Without inflation cage

The tyre must be inflated in two stages.

1st stage:

  • Pre-inflation up to 1.5 bar.
  • General inspection of the tyre: if there is any blistering, distortion or any doubt, the tyre must be removed and inspected by a specialist.

2st stage:

  • Inflate to the correct pressure.
  • To protect him/herself from any blow-out that may occur, the operator should be positioned in line with the tread pattern, at a distance of 3 metres.

Throughout inflation:

  • The tyre must be standing vertically in a fitting area.
  • The operator must be equipped with a hearing protection.


A tyre that has been running under-inflated must never be inflated up to pressure again without a meticulous inspection of the interior of the tyre by a specialist. The weight by axle under load is the only way to determine the right pressure.


Tyre and rim servicing can be dangerous and must be done only by trained personnel using proper tools and procedures. Failure to read and comply with all procedures may result in serious injury or death to you or others. Re-inflation of any type of tyre and rim assembly that has been operated in a run-flat or underinflated condition (80% or less of recommended operating pressure) can result in serious injury or death. The tyre may be damaged on the inside and can explode while you are adding air. The rim parts may be worn, damaged or dislodged and can explosively separate. A tyre that has been running under-inflated should not be retumed to service until the interior is carefully inspected.