[trojwl]

This is the first time I have heard of the chalk method.

Since you have non-stock wheels/tires, it may be difficult to find any published psig recommendations specific to your car.

Do not use the psig stamped on tire. A lot of people misunderstand this psig value. This is a max allowable psig only and you will most probably end up being overinflated if you use it.

When a manufacturer comes up with recommended tire pressure for one of its vehicles, it does so empirically. The optimal psig is the result of tire/wheel design and vehicle weight. The mfgr recommended psig is the pressure that will give the optimal contact patch on the ground. In fact they probably use a much more sophisticated equipment that simulates the chalk method.

This is why a lighter car will usually have a lower psig rating.

The chalk method seems pretty clever to me.