Should PIP tire pressure be the same on all tires?

I set them all the same, just to simplify rotation. Seems fine.

 

Yes, the door panel says 35 front / 33 rear. I told my tire shop that I want them a bit higher, so they set them at 38 front / 36 rear.

I've run 40 all around before though (on different tires), and it was fine.

 

hard to figure how the mfgs decide on tyre pressure. i run 42/40, but have no idea what 40/40 would affect.

 

42/40 gives better mileage but a bumpier ride than the mid-30's.

 

agreed, very firm.

 

I think this is one of those things that comes under the heading, "measurable but not noticeable." Toyota says it's about weight distribution and handling, thus the 2 psi difference, front to rear. I run mine at 42/40 for economy and longer tread life, but as bisco said, the ride is very firm.
Recently I had the warning light come on, but couldn't determine from driving at low speeds which tire was low. (Nor by visual exam).Tire gauge determined the left rear was down to 30 psi due to a nail. I've seen a racing driver demonstrate the ability to detect a tire being down by as little as half a pound just by driving on the track.
Note: reset the tire monitor if you adjust the pressure significantly, and recheck your pressures after service or rotations. They almost always lower the psi.

 

Not a PiP, but I had all 4 tires up to 44psi on the Sonic. After going over a patch of compacted dirt in a parking lot, I noticed dirt across the entire tread width of the front tire, but only the middle of the rear. So I keep the rears at 42psi now, and I can tell when they have dropped below 40psi by the ride.
There were reports of uneven wear of gen2 tires kept to the manufacturer specs. The wear was on the outside of the tread, a sign of too low pressure.

If you aren't pushing the max pressure on the tire sidewall, I don't think the 2psi difference will make much difference if it is there or not for everyday driving. Also keep in mind the numbers on the door are for OEM tires. A different brand or even model may behave differently at those pressures.

 

what to do when changing tyre models, if you want factory recommendation?

 

Experiment. The factory values are probably fine. You can start there or max sidewall and adjust things until you reach a pressure that works for in terms of ride comfort, traction, and rolling resistence. Sprinkling flour on the driveway and driving over it, can let you know if the tire pressure is causing the middle of the tread to only contact the road.

If you rather not do all that work. Get a basic tire tread depth gauge, they are like two bucks, and regularly measure your tires. Do so at the middle and sides of the tread on the tire. This way, you can catch uneven wear early, and adjust the pressure accordingly.

 

I'm extremely sensitive to a car's handling and if you're like me you'll experiment to find the best front/rear pressure. It's complicated because the performance goals, braking, cornering, fuel economy, and wear can each have a different optimum pressure.

I first start with the manufacturers recommendation and then test for tire hop over broken bumpy pavement while at or near the tires cornering limit. Adjusting the pressure until front and rear hop is minimized and equal. With this established pressure I'll adjust if wear, comfort or steering feel is too compromised.

For my Prius Plug-in's stock Bridgestone Ecopia EP20 P195/65R 15 89S tires I used 40/34psi.. I never liked the tires and replaced them at 40K miles. The new tires, Michelin Premier A/S P195/65R 15 91H have been best at 38/32psi. with much better performance.