Tire PSI

Door plate recommendations are the automaker's choice for best balance of vehicle characteristics they prefer to promote.

You're free to change them, as long as you stay within specs. With tires, that means not to exceed the cold PSI rating. 45 on a tire rated for 50 is just fine. I've been doing that with my Prius for over a decade now.

 

The factory pumps up the tires to high pressure for their Pacific Cruise, to prevent flat-spotting or whatever on that long journey. The dealers are supposed to reduce it to the door placard level during PDI, but many 'forgot'. . Probably just shortcutting.

Many of our Gen3s were being sent out the door with 40 psi. I later heard of numerous Gen4s going out with about 50 psi. With the cars parked and chained down on the ship, and only barely moving on the loading ramps and adjacent parking lots, they are not really constrained to obeying that tire sidewall limit before delivery to the final customers.

I'd think "smoother" was a figment of your imagination, it really should be harsher.

As for more grip? This is a regular religious war, you'll have to choose your own side. Many of us like higher-than-door-placard pressures for various reasons (not including smoothness or ride comfort), while many others disagree.

 

2013 Gen 3 . Keep mine at 41, 40.

 

Yeah, as long as it is above the specified psi on the door placard and below the max rated on the sidewall, you are free to change and experiment. As I understand it, the underinflated tires are the more of problem and especially this time of year when the temperature drops in morning. I can have 4-5psi cold pressure difference in my tires between morning and afternoon.

I had higher tire pressure between 42 to 45psi in my Gen3 and experimented on my 2017 Prime. In the end, for Prius Prime, the tire inflation had very little perceivable effects on mpg, smoothness, comfort, or handling for my driving. I have been just using 38 psi all four corners to give a few psi headroom. I check the tire pressure every time I drive using an external TPMS, but only top off air to adjust back to 38psi cold pressure in morning.

 

Anything between the "recommendation" and the max. shown on the sidewall will be fine.
Choose whatever you prefer, based on some test miles.
Most people can't tell much if any difference......in ride quality or fuel mileage.

Once you decide on "your" pressure, you might want to reset the Tire Pressure Monitor to the new values.

 

Like my gen II & III Priuses, I find that my Prime tracks better and handles highway crosswinds better when I inflate the front tires to ~2 psi over the rear tires. I use 37 front/35 rear.

 

The higher the pressure the better the economy.

Recommended to keep them at or no less than 5 below max sidewall for best tread life and good fuel economy.

Higher PSI = better fuel economy, but with diminishing returns. I run 60 PSI.

Running over 60 PSI for will likely increase tread wear but will hold fine.

Running the flatter 30-35 PSI makes the ride slightly more comfortable at a cost of poorer fuel economy, increased tire wear due to more sidewall flex, and tire heat build up.

 

Very incomplete and unwise advice.
YOU can decide to do whatever you please but in effect advising others to exceed the manufacturers max. safe pressure by 15 PSI is just irresponsible.
Extra pressure reduces the contact patch and, generally, reduces the traction.
Too much and the mileage may actually fall due to tire slippage on the driven wheels.

 

I think you quoted the wrong part of my post if you were talking about my recommendation.My advice was "Recommended to keep them at or no less than 5 below max sidewall for best tread life and good fuel economy."
Care to expound on which part was incomplete or unwise?

This is a given, although in most cases the traction is sufficient. Running tires at max pressure should not cause any problems, otherwise the manufacturer would not be able to spec them as such. Higher pressure is at your own risk.

Care to expound on this? Some people run 100 PSI and do not experience slippage. Of course, it is quite risky running such a high pressure and I wouldn't recommend it. We aren't running bare metal wheels with no rolling resistance, and the Prius isn't a race car, so your suggestion of slippage is a bit absurd given the type of car this forum is about. If you're driving hard enough to spin the tires, then you need to evaluate your driving habits. Tires can spin even with <30 PSI.

 

The simple fact that you said: "I do this" implies a recommendation.
And I did not say "spin" but "slip".
But I quit.
This obviously is another case of: "Don't confuse me with facts because my mind is made up".
And / or "how dare you
disagree with something that I said."

 

It's alright, I understand that you happened to misread it, it's okay to admit that. "I do this" is definitely not always a recommendation.

Enough off topic chatter though.