Things were so simple with my ICE vehicle, set the tire pressure to about 35 psi and that was that. The SE recommended pressure (sticker inside door) says 38 psi front, 35 psi back. But my SE came set at 44 psi and my tires (Goodyear Eagle F1 Asymmetric 3) are rated to 50 psi. I saw somewhere that "shipping pressure" is 44-48 psi, but I also had a high school physics teacher who told our class he always went to 60 psi for better gas mileage (and a stiff ride). So what would be ideal for the SE in terms of range? Inflate closer to the max pressure to minimize friction? I really haven't noticed the ride being uncomfortable at 44 psi.
Personally, I'd start at the recommended 38/35 psi, then adjust upwards in small increments based on handling (i.e., steering, braking), comfort, range, and tread wear. Jacking the tires up to a really high pressure right off the bat might (or might not, depending on how smooth the road is) minimize rolling resistance, but is likely to compromise handling and comfort as well as result in uneven wear. OTOH, manufacturer-recommended pressures typically give up some performance in return for greater comfort. (I run the tires of my non-Mini non-sports car at +2 psi in the front, +0 psi in the rear, as that seems to be the best overall compromise for my purposes. YMMV.)
50 would be the max the tires would be 'ok' with... if 44 feels fine, run with it. I recently had new tires put on one of my ICE vehicles (2002 Ranger) and the tires are rated for 50 as well, and the tire shop put them at 45. Felt fine, better than the old tires in-fact. Recently when I went for an oil change at my usual place, they deflated them down to 35 all around and it felt like driving in porridge... so I re-inflated them back up to 45. Long story short - so long as you are under the max rating for the tire and it feels good for you, go for it. just beware hot days if you are running close to the max and keep an eye on pressures on cold days if you run something on the low side for more comfort.
I've had plenty of experience with "low tire" due to extreme cold. Minnesota winters are serious business. In fact my current tires are wholly unsuited for winter, but my service department advised waiting "a couple of months" for MINI to have recommended tires. We'll see how that goes.
"Shipping pressure" is intentionally much higher than you should typically drive on in order to prevent flat spots developing while the car sits still for several weeks. I would expect the dealership's Pre-Delivery Inspection process to reset them to the recommended pressures. Note that different tires respond differently to higher/lower pressures, so I agree with @CuriousGeorge's recommendation to start at the manufacturer's recommended baseline and adjust pressure in small increments until you find the balance you're looking for. (Especially when you choose a different brand/model/performance type.) I also agree with @Toi to be aware of running too close to the maximum rated pressure of the tires. The general rule of thumb is that a 10°F temperature change will result in a corresponding 1PSI change in tire pressure (if you're using "regular air" instead of nitrogen). TireRack has a few tech articles on tire pressure, including this one about when & how to set it. Check out the related links on the right-hand side of that page for even more.
So resurrecting this old thread...has anyone experimented with their tire pressures, and if so, what do you prefer? FWIW, I finally got the title for my new-to-me SE and was able to take for a nice spin. Didn't push it really hard through any corners, but the couple of hairpins and one roundabout I went through left me thinking that more than 35 psi in the rear might be helpful. At that pressure (tires recently inflated when cold...although I can't actually speak to the accuracy of my tire gauge!), it felt like the rear sidewalls were flexing then rebounding, leading to a bit of wallowing. Nary a peep out of the tires, though, and only slight understeer. Pirelli P7s, temperature 55-60 deg, sunny, dry asphalt, decent condition.
Hah. I was just about to write in a different thread about my tire pressures. We were talking about “wet” air the other day, and I was going to order a desiccant module to put inline with my coalescing filter after I noticed the TPMS reporting 33 and 31 psi during the cold snap (I had inflated my 16 inch Nokian winters to 42/37 in November in a 15°C garage). Instead, I ordered a whole new three module unit yesterday with a particulate filter, coalescing filter, and desiccant module. FWIW, my car’s TPMS always reports one or two below my pretty accurate gauge. I generally always run about +2 all around, but I found the 17” Goodyear F1 summers were very happy at the stock pressures.
Higher pressure is best for range, but will have a negative impact on handling and ride as others have said. I run mine at sticker pressure. It looks like this is about the optimal pressure for grip without rolling the sidewalls. My car came with tyres at 35 all round, so someone messed up. I fill mine with dry air. I use a Horror Fright inline desiccator. I think it was $8 or so. The quick fittings fell into my toolbag at work.
Another resurrection here, sorry. Just slapped on the 16" Nokians for the next five months or so and set them at the label pressures (38/35) but that's for the 17" OE tires. Is it a different label on cars that shipped with 16s?
I filled them cold on Friday to 38/35 and the TPMS showed the same when I reset. I checked the TPMS cold this morning and they were at 36/34. ¯\_(ツ)_/¯
