[b] Got new tires which recommends 40psi for the particular tire.[/b]
Maximum pressure: The tyres have a maximum pressure that they can be safely handle. You want to use. In this case you seem to be suggesting you want to use it at the max listed on the tyre, so as far as the tyres go, that should be fine.
Ride comfort: You seem to accept the harsher ride and since you are the only judge of that, then that should also be OK.
Safety: This is the one that I can't offer a yes or no answer. While all the authorities (see below) agree that the pressure listed in the owner's manual is the recommended proper pressure by all authorities, it must be acknowledged that there likely is some amount of flexibility.
Car manufacturers are concerned with many things. They want people to be happy with their cars and that means they want the car to give good mileage and the want the car to ride comfortably.
I have yet to see anyone who has access to real test track facilities and actual test results on modern cars and tyres, offer objective data to support the idea that pressures higher than that recommended by the manufacturer are as safe as the recommended pressure.
My opinion is that a few psi over the recommended value is not likely to compromise safety by any material amount. I would also suggest that there is a point where higher pressure will reduce safety enough to make a difference.
If mileage is more important than safety, go ahead and keep upping that PSI. Other wise, I would suggest reading the following and going along with the professionals. If it really was safe to go higher, then I don't think all the authorities are going out of their way to tell us to use what the car manufacturer recommends.
This is sponsored by a tyre manufacturer Bridgstone - Firestone and instructs the reader to check the owner's manual for the correct tyre pressure.
Here is another from the Goodyear site.
Proper tire inflation is a key ingredient in driving safety and long tire life. It is wise to check your tire's inflation at least once a month with an accurate tire pressure gauge. Continuous loss of inflation pressure is an indication of a possible tire/wheel assembly problem; consult your tire professional immediately if you encounter this situation. Be sure to check the pressure while the tires are cold, and have not been used recently. If you drive even a mile this will cause your tire pressure to increase and give you an inaccurate reading.
Check Your Air Pressure
Keep your tires properly inflated and you could improve gas mileage by more than $1.50 every time you fill your tank. The recommended tire pressure for your vehicle is located on a sticker inside your driver-side door or noted in your owner's manual.
You might also try the US Department of transportation.
You can find the correct tire pressure for your tow vehicle in the owner?s manual or on the tire information placard.