Low Profile tires have different inflation suggestions than regular sidewall tires... width also dictates pressure.
Point is... The tire manufacturer makes several tire sizes, each with their own pressure recommendations, based on their testing of their tires.
If you go by the pressure amount on the gas filler cap (32ish psi), then you will burn through the tread life on a 50psi tire in no time flat.
Assuming your tires are rated at 50psi Max pressure, subtracting 10% (5psi) would be the minimum "minus" pressure... 45, 44, 43, 42psi would be fine, tuned further based on how you like the ride.
Made you a cold pressure/ axleloadcapacity list for both tires, with build in maximum reserve, at wich comfort and gripp is still acceptable.
For that I give 90% of calculated axleloadcapacity for 160kmph/99mph, wich then is maximum speed to use.
First googled the given sizes, these low aspect ratio tires are almost always XL/reinforced / extraload, and only found XL googling.
Front 235/35ZR19 91Y maxload 1356 lbs AT 42 psi upto 99mph.
Rear 255/35 R 19 96 Y maxload 1565 lbs AT 42 psi upto 99mph.
In front of cold psi for front axle, behind for behind. Logical way I think.
Yes, changing tire pressure will change handling. A 'soft' low pressure tire will have a lag in response. A 'hard' high pressure tire will have a more quick response. But, there are other consequences as well. Too high tire pressure transmits pothole shocks that can damage the rim (and other components). Too low tire pressure does not protect the rim either. (there are plenty of threads here about cracked rims. I have repaired two.) Around the City, I have close to 'normal' pressure due to bad roads. For my long distance 'Autoput' driving, I run higher than normal pressure. Load factor (as mentioned above) and temperatures will also have an effect. Your tires are your only contact with the planet surface. I support your attention to them.
Pirelli 19 inch 275/30 on the rear 9 inch rims and 245/35 on the front 8.5 inch rims
Around town I run 42psi
On the highway for less rolling resistance and better fuel economy I run 45psi
The wheels look nice when you get rid of the rusty rotor hubs by painting them silver
and the stone guards silver as well, and paint the brake calipers red.
A 7.5 inch alloy rim will fit in the wheel well if you want to ditch the junk space saver spare wheel
Just pay attention to the size of the tyre you fit so that it is close to the same circumference as the others on the car
Personally I do not like harsh rides. Setting at 40+psi is too harsh for me.
Run mine at 35/36 psi cold. When hot they reach 39/40, perhaps 41 in the middle of the summer, and running hard on the highway.
Vehicle @98K miles on the 2nd set of ContiContact. First set lasted 50K+ miles. Currently rear ones have 8K left at best, front ones easy another 15/20K.
NOTE: never rotated either set, and the car was checked (no alignment required) for alignment at the 50K miles service. My car is still speed limited, so the maximum speed on either set has been around 120mph
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