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Discussion Starter #1
I have a very accurate, professional grade tire gauge.....found that the cold pressure reading of my tires was 38psi....three over the rec. When I was rolling .... checked the pressures via the dic info page and they were up to 41!!!! So.....took the cold pressures down to 35 and now the "hot" rolling pressures are up to 37/38....much better road feel!
I did read somewhere that many vehicle manufacturers over inflate the tires prior to transport.....but the dealer should have checked that and taken the pressure down. The other important aspect of this is that these are "low profile tires" and they will "heat up" quickly and pressure will rise much faster than "normal ratio" tires! ....get a good gauge and check those pressure readings....better ride, better tire life!!
 

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18 LEXUS LX, 17 Rav4, 15 Escalade ESV, 14 Mercedes, had Vette, 2Cadis, T-B & Chevy
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I Mercedes manual says to add 4 pounds to each tire when planning on driving over 100 MPH.

Most of the manuals that I have read over the last several decades say to inflate the tires to their maximum close to their P value for maximum tread life.
I did this on my Corvette for decades and the tires last a very long time. Each five years I replaced the tires on the Vette and the mechanic said the tread was in excellent condition like new and I had an average of 20,000 miles on the tires each five years.
 

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18 LEXUS LX, 17 Rav4, 15 Escalade ESV, 14 Mercedes, had Vette, 2Cadis, T-B & Chevy
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My corvette tires were only designed to last around 10,000 miles and got 20K with no tread wear.
just microscopic tires rot from age after 5 or so years.

65K miles, I never had tires that long.

most of my tires get replaced by time not wear.
maybe it is because I have too many cars.
 

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Recommended pressures are cold. It's normal for them to increase as you drive and the tire heats, but you shouldn't deflate them to reach the recommended when they are hot. They will return when the tire cools.

Ride softness is the only reason to decrease pressure. Load capacity and cornering increase with pressure, so higher pressure is normally better for longevity.
 

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To a point. Too high a pressure will just accelerate wear down the center of the tire.
 

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To a point. Too high a pressure will just accelerate wear down the center of the tire.
Not so much with modern steel belted tires. You would have to significantly over inflate to wear the middle. More likely, an under inflated tire will tend to roll the sidewalls under in corners, so the edge of the tire tread wears much faster when pressure is low.
 

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I have always added pressure when the tires are cold but stay about 4# from the max.
The 4# increase will come from driving as the tire warms up.

I have not yet changed what the dealers recommended and set the tires at.
On my Escalade I think the dealer set them for 38#.
I think my Mercedes was set by the dealer at 36#.
 

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Higher pressure is never unsave for the tires.
The given maximum pressure written on sidewall is the maximum cold pressure the tire-maker alows.
this is not the pressure at wich the tire is allowed to bare its maximum load up to 160km/99m/h, wich is also given on sidewall as loadindex or maximum load.
This pressure I will call AT-pressure further. For P-tires ,AT-pressure is 35psi in American system ( EUR 36 psi) .
But most likely your low Hight/Width division tires are XL/reinforced/Extraload wich have AT-pressure of USA 41 psi, EUR 42 psi.
I once got hold of the official formula to calculate pressure for lower then maximum load.
So dont be afraid of the higher pressure .
I once read that tires are tested to stand an absolute pressure of 2 to 3 times the AT pressure .
So a P-tire will blow somewhere between70 psi and 105 psi. A XL// tire between 82 and 123 psi.
Tire pressure advice is all about load on tire in ratio to maximum load , and speed you maximaly drive.
A bit about alighnment ( camber angle).
For lower speed the tire is allowed higher maximum load for the same AT-pressure .
And vice versa higher speed lower maximum load.
 

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Good info!

Also, along a similar line, Sewell uses nitrogen in the tires to reduce pressure change from temperature...same as aircraft tires. Is this standard practice, or just Sewell?
 

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Discussion Starter #12
Higher pressure is never unsave for the tires.
The given maximum pressure written on sidewall is the maximum cold pressure the tire-maker alows.
this is not the pressure at wich the tire is allowed to bare its maximum load up to 160km/99m/h, wich is also given on sidewall as loadindex or maximum load.
This pressure I will call AT-pressure further. For P-tires ,AT-pressure is 35psi in American system ( EUR 36 psi) .
But most likely your low Hight/Width division tires are XL/reinforced/Extraload wich have AT-pressure of USA 41 psi, EUR 42 psi.
I once got hold of the official formula to calculate pressure for lower then maximum load.
So dont be afraid of the higher pressure .
I once read that tires are tested to stand an absolute pressure of 2 to 3 times the AT pressure .
So a P-tire will blow somewhere between70 psi and 105 psi. A XL// tire between 82 and 123 psi.
Tire pressure advice is all about load on tire in ratio to maximum load , and speed you maximaly drive.
A bit about alighnment ( camber angle).
For lower speed the tire is allowed higher maximum load for the same AT-pressure .
And vice versa higher speed lower maximum load.
I would suggest too broad of a conclusion.....all tire manufacturers will tell you, "over or under inflated tires can be dangerous" The vehicle manufacturer has indicated on the affixed label the recommended pressure and also warns that "over or under inflation" can be dangerous. Exactly at what pressure point involves not only the particular aspects of the vehicle( gross vehicle weight and load capability ) but abilities of the driver. I determined that the 38psi COLD pressure that my vehicle was delivered with was allowing the heated pressure to rise to 41+ .....too harsh for me, given the combined 22in wheels and low profile of the tire. I find the ride to be softer and "quieter" now that I have gone to COLD pressure at the recommended 35.
 

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I have found through years of GM vehicle ownership experience that whatever the DIC shows as the displayed tire pressure is not correct. The displayed tire pressure being shown on the DIC is 2 psi lower than the actual reading at the valve stem. I don't know why GM Engineers haven't just taken an algorithm/formula and programmed the sensors to display the correct tire pressure. GM's tire pressure sensors have shown the exact same deficit since the 1997 C5 Corvette introduced on board real time tire pressure sensors.
 

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It's been my experience that the vehicle recommended pressure is always on the low side, I assume for best ride comfort, while still giving the tire the weight carrying capacity needed. The high end pressure is molded into the sidewall. This range, measured cold, would be the safe range. Unless your cold pressure is below or above these, you will not be unsafe or dangerous. But, ignore hot pressure. It is not relevant except for mere curiosity.
 
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