Tire Pressure

[Misho]

Could anyone explain what are the advantages and/or disadvantages of over and under inflating tyres ??

I heard once that its good to slightly under-inflate the tyres below the suggested pressure as that helps "relax" the shocks.

And on my dad's car manual it says that for normal driving 28f/26r psi is good, while for high speed driving 35psi is suggested.

Could anyone explain please ?!

[megotmea7]

you tire pressure is dependent on were your driving: for example if you driving at high speed adding more air than normal decreases rolling resistnace from the tire and decreases the heat produced form traveling at higher speeds, under inflating tires usually creates a larger contact patch and increases grip somewhat, the underinflating to have a better ride s true alson because if you think of a baloon when you blow it half way up and squeeze it is more kooshy than if you blew it all the way up same thing applys to tires, underinflated tires also decrease gas mileage and underinflated tires can help a heavy car or truck travers sft sand or mud situations by alowing it to "float" over it but that doesnt mean take your civic out to the desert put 10psi all around and think your not going to get stuck it only help, and little at that it mostly helps on bigger tires too

[NoOne]

You are totally correct megotmea7 , if I could just add in RWD drag racing it is common practise to over-inflate the front tires to decrease rolling resistance(friction) and at the same time run lower pressure in the rears to increase contact patch for better grip, of course there are limits in both directions.
:D

Later.