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Discussion Starter #1
I'm calling this an odd question for a couple of reasons but mainly because the door jam says 35psi and where I live (temperature). When I picked up my car I watch the service guy go over the car. Even saw him check all the tires and he put some air in two of them. While driving it home I was playing with the EVIC and saw I was running at 39-40psi. I immediately thought that was high but then thought "these are performance tires maybe they are suppose to be that high". when I got home I check the door and saw the 35 recommendation and figured they put too much air in. After doing searches in here I found out that psi will change much more than I though based on temp and they should be checked "cold". Here is where I'm confused though. I'm assuming "cold" means the tire itself right? Not the outside temp? I checked them yesterday with a gauge before I drove it and I was still at 38-39. After driving about 8 miles over to my girls house I checked them again and they read 38-40. Not much of a difference. I live in FL so the outside temp is almost always above 60 so that's where I'm confused with the "check when cold" part. Yesterday I dropped them down to 36 and they seem to be running about 37 now on the EVIC. Should I drop them down even more to run at 35? I initially thought they were set at 35 at the Brampton plant but now in FL they went up to 40 with the temp but then I remember seeing the service guy put air IN them. Im pretty sure I should be at 35psi but I just wanted to check here. Btw they ate the F1s and this is for street use not racing. Sorry if these question seem stupid because at first it seemed pretty clear cut to me but after reading about changing temperature and the guy putting air in the tires it threw me off of what should be pretty straight forward.
 

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Cold tire pressure refers to the temperature of the tire, not the ambient air. The best time to check the pressure is in the morning before the car is driven. Hot tires can raise the pressure 1 to 2 pounds typically, more with really aggressive driving or many highway type miles.

I run higher pressures in my tires than recommended on the door jam (my car states 32 psi). I run 35 in the rear tires and 40 in the front tires (max pressure is 44 on these tires). I rotate my tires regularly (front to back) and there is still a lot of life left in them at 41,000 miles.

The recommended pressure will provide a somewhat softer ride. You will have to decide for yourself where to set your pressure.
 

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Discussion Starter #3
Thank you. So 40 isn't an issue than. I think my max psi is 51. What's your reason for running higher psi in the front than the back? Better traction for rear and less wear in front? I may try that. As for ride quality, I could probably put solid rubber tires on and would still be better than the trucks I've been driving for the last 10 years
 

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The TPMS system is calibrated for the PSI on the door jamb. If one ever goes LOW, you have to get all 4 back up to the cold pressure for the system to be happy again. It's all in the owners manual.
 

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Discussion Starter #5
The TPMS system is calibrated for the PSI on the door jamb. If one ever goes LOW, you have to get all 4 back up to the cold pressure for the system to be happy again. It's all in the owners manual.
Yeah I get that, but my question is more of the tire pressure being too high from when I took delivery. Not too low.
 

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The recommended tire pressure is calculated on many factors and assures that the proper amount of tread is on the pavement. Running it too high will reduce the edge contact and wear the center faster and MIGHT even cause a loss of traction due to the narrower footprint.

Running too low does the opposite and can cause excessive edge wear and too much flex as well as excessive heat buildup.

Of course there are exceptions to this rule but unless you are racing set them to factory recommendation.

Check your pressure when your tires are cold and inflate them to the recommended pressure.
 

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Yeah I get that, but my question is more of the tire pressure being too high from when I took delivery. Not too low.
Forget that, it's ancient history unless you put thousands of miles on them. Just set them to factory specs and enjoy your car. Don't over-think this.
 

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Yeah I get that, but my question is more of the tire pressure being too high from when I took delivery. Not too low.
Mine was the same way on delivery, overfilled, had 39 to 40 in each one and rode like a brick, don't know if it was dealer or Brampton who did it.
 

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As noted, check tire pressure when the tires are cold. A good practice is to check them in the morning before the car is driven. As a side note, if the morning sun is shining on one side of the car the tires on that side can actually build PSI slightly from the sun’s rays verses the side not in direct sunlight.

The max PSI noted on a tire indicates the max cold PSI that can be placed in the tire assuming the load rating on the tire is met. Typically you will not load a passenger car with enough stuff to equal the load rating noted on the tires. On the other hand, this is important for trucks and trailers.

The PSI noted on the placard on the door jam is the recommended PSI to provide you the most comfortable ride and handling. Tires are 1 of 3 components design engineers factor in / design to for ride comfort the other 2 being springs (suspension) and the seats.

If you were to track your car you would want to fill the tire to the max PSI to reduce as much side wall roll as possible when cornering hard but the ride of the vehicle will be like a brick.

One other note, lower profile tires will heat up resulting in increased PSI more / faster than a higher profile tire. It is simply a case of the lower profile tire cannot shed heat like a higher profile tire can.

And the last note, the recommended PSI noted on a car’s placard assumes the brand and size tire that came on the vehicle. If you change tire brand or size you should start at the recommended PSI and then you will have to play from there to see what PSI gives you the best ride comfort and handling understanding ride comfort and handling are always a compromising situation.

Oh, never trust the tire pressure gauge the guy at the tire place or dealership is using. Typically, drop a tire gauge once and you might as well throw it away.
 

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Best to check pressures when car has sat (out of sun if possible) at the cooler time of the day.

Pressures will rise when driving and when ambient temps get high. I've seen 39-40 driving on a hot summer day from the setting of 33.5 that I use.
Placard states 32psi for my year.
 

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If you don't own a compressor fill the tires to 40 at night before you go home for the day and first thing in the morning let out to 35 psi.
 

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Discussion Starter #13
Thanks a lot guys. I'm just going to set them at my place card recommendation tomorrow morning before the sun comes up. I was just all thrown off by the initial high reading right from the start.
 

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I just thought it was interesting how you have 35 psi printed on your door panel. I thought pretty much everybody's was printed 32 on these cars. I do agree, though, 32 is a bit soft for my tastes. I've been hovering around 34/35, lately. For a while I had a whopping 36 in my rear tires, but that was clearly causing the center tread to wear preferentially.
 

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. . . What's your reason for running higher psi in the front than the back? Better traction for rear and less wear in front? . . .

I run higher in the front for even wear since these are the turning wheels. Traction is not a concern for me with the rear tires since I don't drag race my car. I have found over my 40 years of driving that the front tires often wear on the edges more quickly than the center. This wear pattern seems amplified with front-drive cars or if you take turns aggressively.

I rotate my tires as often as 5,000 miles and measure the tread across the tire to be sure they are wearing evenly. Most people likely don't pay as close attention to the tread. Another benefit of measuring the tread depth somewhat frequently is you're likely to find alignment problems before you trash the tire(s).

YMMV
 

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Discussion Starter #16
I just thought it was interesting how you have 35 psi printed on your door panel. I thought pretty much everybody's was printed 32 on these cars. I do agree, though, 32 is a bit soft for my tastes. I've been hovering around 34/35, lately. For a while I had a whopping 36 in my rear tires, but that was clearly causing the center tread to wear preferentially.
Mine say 35 because I'm an idiot. It does say 32. Must have been because when I looked at it it was dark out and I thought the 2 was a 5. I decided to drop mine down this morning (that's when I noticed it said 32) to just under 34 and Ill see how it rides and what the EVIC says after a drive. Took it for a 200 mile ride yesterday and that was my deciding factor to drop it. Glad I did so far because now I know it says 32 not 35. It's only 3 psi but when they were at 40-41 when heated up that's a big difference IMO
 

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It's a big difference in feel between 32 and 35, even only 3 clicks apart. ;) At 32, there is isolation from a great deal of road noise and vibration...could almost say it is "cushy". At 35, you feel every single bump and imperfection in the road, and you can tell the road texture by the road noise that comes into the cabin.
 
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