I've heard this on other threads and heard arguments supporting higher tire pressure too with the only drawback begin a harsher ride. Yesterday we did 130 highway miles and started at 44 psi, ended at 46.5 psi. It's hard to know what to believe but if it's dangerous to run 45psi then why would a manufacturer put 51 psi max on the sidewall?
I should add that my driving style may not stress the tires much (see below)
I don't disagree with irpilot; however, I'm going to respond just one more time to try and help you understand to save your life, your passengers lives, and the lives of fellow drivers around you, but this is the last attempt. I do apologize to others for the length of this write-up, but I hope you read it through carefully (multiple times if necessary).
In response to your 2.5 PSI increase, unless your on the south side of the hemisphere experiencing summer season, right now we're reaching colder weather temperatures. So, the ambient cold air will keep the tires cooler such that they don't expand as much and/or as fast as in the heated weather (in the heat you'll likely experience roughly around a 5-6 PSI increase if not more). Also, elevation/altitude can affect tire pressure as well (air is thinner, etc.). With that said, that does NOT mean you can safely drive with higher PSIs in cooler weather. What it means is what you're seeing in the low PSI increase is POTENTIALLY reasonable in the current temperature. I bet if you were in roughly 90F+ degrees, your tires could easily hit close to 50 if not exceed 50. That's how much it can potentially expand both in the heat and at consistent high speeds.
Now, in terms of the tire's "Max" PSI, you have to remember that this is the tire manufacture's spec not the car manufacture's. The tire company did NOT engineer/design/develop/build your Pacifica. Chrysler engineers did. Now, if you want to make the argument that you should be able to run higher PSI on your tires that exceed standard manufacturer recommended PSI, it means you're hauling a ton of cargo such that the increased weight within the vehicle offsets the added pressure thereby pressing down on the tires enough so that the entire width of the tread contacts the pavement. If you're not hauling a large load, then overinflating does everything bad that I've mentioned before and will try to rephrase below to see if it helps you understand better. Now, it doesn't mean that if you're not hauling anything that you should underinflate your tires. The manufacturer's recommended PSI accommodates single passengers plus additional passengers. With that said, you should view the tire manufacturer's max PSI as part of maximum load in which the vehicle can haul. There are calculators online you can search for that'll calculate vehicle cargo load weight to additional suggested tire PSI. In fact, usually the car's driver side b-pillar or the manual will state what PSI to set the tires based on load which can easily be referred to as well.
As for the "only drawback being harsher ride", this is only part of it. As I said, if the sides of your tire treads are off the pavement and the center is on, only the center wears which creates uneven wear. This is just common sense. Next, with less rubber contacting the road, you're essentially crippling your handling and traction ability. It's why race cars use fatter tires for better grip, greater tire to pavement contact, etc. They're not running skinny tires for a reason.
Lastly, if you go to Chrysler's site > Owners > Owners and service manual > Tire Info Supplement. You can say they're printing these warnings to avoid lawsuits. Honestly that's partially true. The other 1/2 is simply because they don't want you killed in their vehicle because that's 1 less person to continue buying their vehicle in the future. So, unless you're a automobile/tire engineer, you should really consider trusting the manufacturer who hires engineers to design a car that will not kill you if operated properly as designed. And, if you don't trust them and what they "suggest" is proper operation, you should not own their car or any car for that matter because all car manufacturers do the same with suggesting a proper PSI which at the moment you continue to disagree with and disregard. And finally, if you really want to still own a car and want to disregard the manufacturers, there's a ton of research to be found on google with answers from tire experts such as Tirerack.
From the official Pacifica manual -
Overloading of your tires is dangerous. Overloading
can cause tire failure, affect vehicle handling, and
increase your stopping distance. Use tires of the
recommended load capacity for your vehicle. Never
• Improperly inflated tires are dangerous and can
• Underinflation increases tire flexing and can result
in overheating and tire failure.
• Overinflation reduces a tire’s ability to cushion
shock. Objects on the road and chuckholes can
cause damage that result in tire failure.
• Overinflated or underinflated tires can affect vehicle
handling and can fail suddenly, resulting in
loss of vehicle control.
• Unequal tire pressures can cause steering problems.
You could lose control of your vehicle.