Good question and I''ll be interested in the other responses you get. I have 185-70-14 tires. It was recommended to me to use 31 psi all around. However, with my car, this results in very "twitchy" steering and going over bumps is harsh. I prefer 29 because there is a bit more resistance in the steering and I get an overall smoother ride. I am not into street racing so this advice is for general drivability, using original front suspension components.
I did make the mistake, for about 2 months, of using the pressures recommended in the original owner's manual (I believe something like 22 in front, 24 in rear) but these values were based on the very different tire design in those days. You get a great upper body workout trying to park the car with these low pressures but you also put excessive strain on the steering box which is aluminum and might eventually crack.
I don't think that there is an optimum tire pressure that fits every car because of variables like suspension and alignment settings, size and make of tire, use of vehicle and driving style. It's a process of experimentation to arrive at what you think works best for your application.
For another datapoint, I ran a 1750 GTV with 185/60 14 Yokohama A032R tires set at 32psi cold front and rear. After a few hot laps, the pressures ended up at 40 front and 38 rear; just about perfect for the cars settings and my driving style.
I also run 32psi front and rear - Falken G tyres - 205/60R14 88H. Yes, the car is a little twitchy but I like it like that. Going over bumps you do feel like someone punched you in the kidneys, but the steering is nice and light and it sticks on corners like s**t to a blanket.