I have a '99 E430 Sport. The other day I observed my back tires were at 23lbs pressure and the front were at 28 lbs. This was after driving all day so the heat had already built-up the pressure.

The tires I use say Max pressure is 44lbs. Should I have them inflated to 35lbs or 38lbs. What's the best amount of pressure for performance and life of the tire?

When is it best to check the pressure first thing before you drive or after the tires have heated up? Also I live in Miami, a hot environment, so the driving conditions are always hot.

tire size: 235/45 ZR17 BFGoodrich g-force T/A kows on alloy rims.

 

You always check tire pressure when it's cold.

check the driver's side door pillar, it should give you the PSI of the front and rear tires

 

Agreed with Turbo][ that check your tire pressure while they are cold. I usually check mine early in the morning at gas station less than 1 mile away using a quality tire pressure gauge (the old fashion needle type). I ran the same tire size (Conti Sport Contact 235-45/17) as you but with 32psi front and 35psi rear. The factory setting is way too low for my driving (more like floating going through bumps).

good luck...

 

I put 36 front and back. The car is more stable in turns that way.