What determines my tyre pressure

martineire

Just wondering what determines my tyre pressure. On the diesel flap of my car it shows two sets of pressure you can pump your tyres up to, one is for a fully loaded car and the other is for a smaller load in the car. For example one of the sets of pressures shows 2.2 bar for the front tyres and 2.2 bar for the back tyres

Does the weight of the car determine this pressure, or does the size of the tyre determine this pressure? Say for instance I got new alloys on my car and the tyre size changed from the original size would the tyre pressure stay the same as indicated on the diesel flap???

colm_mcm

There will usually be recommended tyre sizes for different size wheels.
The owners manual should have these listed.

As an example
http://www.puretyre.co.uk/ford-tyre-pressures/

CiniO

martineire wrote: »

Just wondering what determines my tyre pressure. On the diesel flap of my car it shows two sets of pressure you can pump your tyres up to, one is for a fully loaded car and the other is for a smaller load in the car. For example one of the sets of pressures shows 2.2 bar front and 2.2 bar for the back tyres

Depending on the load you carry, you should set pressure accordingly.
Usually bigger pressure (especially for rear tyres) for full load is advised.

Does the weight of the car determine this pressure, or does the size of the tyre determine this pressure? Say for instance I got new alloys on my car and the tyre size changed from the original size would the tyre pressure stay the same as indicated on the diesel flap???

Not necesserily.
Car manufacturer should list advised pressure for all allowed tyre sizes.

jadatis

I kept myself busy with tyre pressure calculation since end 2007, and gathered a lot of information in time.

The needed pressure is to give the tyre a deflection so the rubber does not bend to much that to much energy is produced and transformed to heat at sertain places of tyre.

For that the actual load on tire /maximum load of tyre is most important.
But for higher speed less bending of rubber is allowed because every part of tire is bending and bending back more often. For instance at 80km/50m/h an average tyre bends and bend back about 10 times a second. At double speed 20 times.

then at last if the alignment is with camber angle a trapezium shaped smaller surface on the ground wich needs higher pressure to give the most deflected sidewall stay under the border of damage.

so its a bit more complicated then only the load.
And if the other tyres have more maximum load with the same pressure needed for that, it needs a lower pressure to give it a save deflection.