What is the optimum tire pressure? I have a 2018 Mazda CX-5 GT with toyo a36 225/55r/19's The door sticker say 35psi, Than I read stories that 40 is ideal. For those of you who especially have the 2017 CX-5s. What tire psi have you found to be the best?
Any Mazda owner can chime in.
I wish I noticed this earlier. There really is no "ideal" for everybody. The tire placard pressure is the
compromise the R&D engineers think most people will like. It applies
ONLY to the OEM tires. It is likely a good starting point for other tires.
A mom with a carload of kids in suburbia will want a softer ride and will not be driving fast, so heat is not a problem for her. Her optimum might be 30 psi and absent speed and hard cornering, she'll get good tire life.
At the other extreme, a driver in west TX travelling to distant sales calls, running 10 over the posted 85 mph limit will want much higher pressure so his sidewalls are stiff, reducing heat and increasing control. Pressures over 40 psi will help his tires last longer and be safer.
An autocrosser, the 3rd extreme, is looking for maximum traction and minimum sidewall deflection, so the tread stays as flat on the ground as possible. He will check tire toll-under with chalk on the sidewall and temp across the tread and adjust pressure for the most even temps across the tread. That will likely be 50+ psi. It was for me when running tires that got 32F/30R on the street.
I have winter and summer tires for my Miata. The A/S winter tires are very rough riding, even with Ohlins coilovers. I run them at 26 in the front and 28 in the rear. The placard says 29 psi. My summer tires are Michelin Pilot Super Sports. I run them at 30F/31R. Higher rear pressures are an adjustment to my modified suspension with 25% stiffer rear springs than Ohlins normally supplies. These pressures give both the ride and steering response I like with even tire wear across the tires.
As you can see, What might be "optimum" for me is not for you. As long as you respect the max pressure molded into the sidewalls of the tire and stay above, say 26 psi*, you can run anything you like. Lacking any information to the contrary, begin at the placard pressure and adjust to your liking.
I'm running 36 psi F/R in my OEM 17s.
*I choose this pressure because it was the pressure Ford spec'd for the '90s Explorer that suffered several heat related tire failures. I ran mine at 34F/30R and drove it like my Mustang (i.e. barking the tires in 3rd) without issue.