I have to wonder if tires marketed for the light vehicle market are tested at 32psi. Then OEM's just look at that chart, find a tire with the load rating required, and call it a day. They COULD test to find the optimal psi but that may take more time than they are willing to spend, especially on the lower trim models. Plus there is likely value in using a common number; maybe not so much in today's world of instant computer readout but even then, dealerships and shops are well known for goofing on small details, time to time.
Where did 32 PSI come from?
- Thread starter grampi
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Almost all GM cars, with very few exceptions, for the last 20+ years has had a recommended pressure of 30 psi. The only difference from a smaller car to a larger car was the tire size, but they all called for 30 psi. It's almost like they determined tire size from the load using the same tire pressure on every car from Corvettes to Cadillacs. Weird.
Originally Posted By: SR5
I'm a 36 psi guy and maybe a touch more in the spare.
Found this (Note: it's from Australia so "Utility" means "Pick Up")
Quote:
Small Vehicles
Car Type : Pressure Range : Optimal Pressure
Standard : 30 - 36 Psi : 32 Psi
Sports : 32 - 38 Psi : 36 Psi
Wagon : 32 - 40 Psi : 38 Psi
Utility : 32 - 40 Psi : 36 Psi
Medium Vehicles
Car Type : Pressure Range: Optimal Pressure
Standard : 32 - 40 Psi : 36 Psi
Sports Car : 34 - 42 Psi : 40 Psi
Wagon : 34 - 40 Psi : 38 Psi
Utility : 32 - 44 Psi : 40 Psi
Large Vehicles
Car Type : Pressure Range : Optimal Pressure
Standard : 36 - 42 Psi : 38 Psi
Sports : 36 - 50 Psi : 44 Psi
Wagon : 38 - 46 Psi : 42 Psi
Utility : 40 - 50 Psi : 44 Psi
Here
http://www.ozzytyres.com.au/blog/what-is-the-ideal-tyre-pressure/
SR5,
Thanks for that chart. I hope everyone will understand now that even tire dealers don't know what they are talking about - and they publish stuff that contradicts what the vehicle and tire manufacturers say - further confusing the issue.
The vehicle manufacturers specify the inflation pressure - and they use a variety of methods to arrive at it. In the old days, they frequently picked the smallest tire that would carry the load - hence the 32 psi in the bias tire era.
However, it was discovered that you could get a better ride using a larger tire, but less pressure. It was also discovered that the vehicle behaved more predictably when using larger tires. (short version: Tires operated near the max load/max pressure point would sometimes have large curves in the tire force and moment diagrams. These are flatter when using large tires, even at lower pressures!)
Nowadays there isn't a simple formula that every vehicle manufacturer uses to select a tire size and inflation pressure. For example GM TENDS towards using 30 psi for their cars and 35 psi for P metric tires on SUV's, trucks, and vans - BUT not always!
That's why Tire Guides publishes a book summarizing not only what tire size came on vehicles, but the specified pressure, the rim width, lug nut torque, etc. It gets updated every year - published about January or so!
So I always say: LOOK AT THE VEHICLE TIRE PLACARD! If nothing else, it ought to be a clue where to start. And since 2008, (in the US) it's supposed to be on the drivers door or doorframe!
I'm a 36 psi guy and maybe a touch more in the spare.
Found this (Note: it's from Australia so "Utility" means "Pick Up")
Quote:
Small Vehicles
Car Type : Pressure Range : Optimal Pressure
Standard : 30 - 36 Psi : 32 Psi
Sports : 32 - 38 Psi : 36 Psi
Wagon : 32 - 40 Psi : 38 Psi
Utility : 32 - 40 Psi : 36 Psi
Medium Vehicles
Car Type : Pressure Range: Optimal Pressure
Standard : 32 - 40 Psi : 36 Psi
Sports Car : 34 - 42 Psi : 40 Psi
Wagon : 34 - 40 Psi : 38 Psi
Utility : 32 - 44 Psi : 40 Psi
Large Vehicles
Car Type : Pressure Range : Optimal Pressure
Standard : 36 - 42 Psi : 38 Psi
Sports : 36 - 50 Psi : 44 Psi
Wagon : 38 - 46 Psi : 42 Psi
Utility : 40 - 50 Psi : 44 Psi
Here
http://www.ozzytyres.com.au/blog/what-is-the-ideal-tyre-pressure/
SR5,
Thanks for that chart. I hope everyone will understand now that even tire dealers don't know what they are talking about - and they publish stuff that contradicts what the vehicle and tire manufacturers say - further confusing the issue.
The vehicle manufacturers specify the inflation pressure - and they use a variety of methods to arrive at it. In the old days, they frequently picked the smallest tire that would carry the load - hence the 32 psi in the bias tire era.
However, it was discovered that you could get a better ride using a larger tire, but less pressure. It was also discovered that the vehicle behaved more predictably when using larger tires. (short version: Tires operated near the max load/max pressure point would sometimes have large curves in the tire force and moment diagrams. These are flatter when using large tires, even at lower pressures!)
Nowadays there isn't a simple formula that every vehicle manufacturer uses to select a tire size and inflation pressure. For example GM TENDS towards using 30 psi for their cars and 35 psi for P metric tires on SUV's, trucks, and vans - BUT not always!
That's why Tire Guides publishes a book summarizing not only what tire size came on vehicles, but the specified pressure, the rim width, lug nut torque, etc. It gets updated every year - published about January or so!
So I always say: LOOK AT THE VEHICLE TIRE PLACARD! If nothing else, it ought to be a clue where to start. And since 2008, (in the US) it's supposed to be on the drivers door or doorframe!
Last edited:
Originally Posted By: eljefino
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+1
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+1
Originally Posted By: OneEyeJack
In the old days when people actually survived without cell phones but still had electricity and self-starting cars, they had places for you to gas up called "service stations". You drove and ran over a hose that rang a bell. I human would come to your car and you would say something like fill it up with Ethyl and that's what the attendant would do along with checking your engine oil level, fan belt(s), radiator, P/S fluid, windshield washer fluid and tire pressure. No, honest it's true. . . .
No! Really??? Gosh darn, Grandpa Wally. What other good stuff did we give up from back then???
In the old days when people actually survived without cell phones but still had electricity and self-starting cars, they had places for you to gas up called "service stations". You drove and ran over a hose that rang a bell. I human would come to your car and you would say something like fill it up with Ethyl and that's what the attendant would do along with checking your engine oil level, fan belt(s), radiator, P/S fluid, windshield washer fluid and tire pressure. No, honest it's true. . . .
No! Really??? Gosh darn, Grandpa Wally. What other good stuff did we give up from back then???
Originally Posted By: Benzadmiral
Originally Posted By: OneEyeJack
In the old days when people actually survived without cell phones but still had electricity and self-starting cars, they had places for you to gas up called "service stations". You drove and ran over a hose that rang a bell. I human would come to your car and you would say something like fill it up with Ethyl and that's what the attendant would do along with checking your engine oil level, fan belt(s), radiator, P/S fluid, windshield washer fluid and tire pressure. No, honest it's true. . . .
No! Really??? Gosh darn, Grandpa Wally. What other good stuff did we give up from back then???
-Jumping trough a windshield at a collision
-Going to the moon
-Looking over your shoulder when backing, driving, changing lanes
-Looking at the road, not an LCD/LED screen
-Mullets
-Pink Shirts of the 70's
-Chuck Norris playing a trucker
-Louis DeFunnes
-Sir Roger Moore/The Saint
-Big Cars (But we're getting there)
-.... etc
Originally Posted By: OneEyeJack
In the old days when people actually survived without cell phones but still had electricity and self-starting cars, they had places for you to gas up called "service stations". You drove and ran over a hose that rang a bell. I human would come to your car and you would say something like fill it up with Ethyl and that's what the attendant would do along with checking your engine oil level, fan belt(s), radiator, P/S fluid, windshield washer fluid and tire pressure. No, honest it's true. . . .
No! Really??? Gosh darn, Grandpa Wally. What other good stuff did we give up from back then???
-Jumping trough a windshield at a collision
-Going to the moon
-Looking over your shoulder when backing, driving, changing lanes
-Looking at the road, not an LCD/LED screen
-Mullets
-Pink Shirts of the 70's
-Chuck Norris playing a trucker
-Louis DeFunnes
-Sir Roger Moore/The Saint
-Big Cars (But we're getting there)
-.... etc
Originally Posted By: Tundragod
If you have 36 psi cold, it will be 40-42 psi hot. I've check mine at 32 psi cold and 36 psi hot.
I love how if I set the cold pressure to 33 psi for the G37 in the 10 C garage and pull out in the winter, the stupid TPMS kicks off in about two blocks.
So, I put it to about 36 psi at 10 C to make up for what happens after that.
If you have 36 psi cold, it will be 40-42 psi hot. I've check mine at 32 psi cold and 36 psi hot.
I love how if I set the cold pressure to 33 psi for the G37 in the 10 C garage and pull out in the winter, the stupid TPMS kicks off in about two blocks.
35 across the board for all my rides. Its served me well for years.
Originally Posted By: Merkava_4
I like mine at 36, that way it gives me room for air loss.
If you used nitrogen you wouldn't have that problem.
https://www.youtube.com/results?search_query=1950+full+service+gas+station
I like mine at 36, that way it gives me room for air loss.
If you used nitrogen you wouldn't have that problem.
https://www.youtube.com/results?search_query=1950+full+service+gas+station
Originally Posted By: Papa Bear
If you used nitrogen you wouldn't have that problem.
I use air that contains about 78% nitrogen and find it works well enough and is much cheaper.
Play this video for the real world of nitrogen in tires...
If you used nitrogen you wouldn't have that problem.
I use air that contains about 78% nitrogen and find it works well enough and is much cheaper.
Play this video for the real world of nitrogen in tires...
Originally Posted By: Eddie
I was one of those guys who, when the bell rang, ran to your vehicle and asked how much gas, wiped your windshield and checked your oil. I waited for the tip but, it very seldom happened.. WARCO STATION in Rock Island ILL ~1955. Ed
We had THREE guys running to your car at Texaco in the late 60's. Each of us had a wad of cash for change and we would check under the hood, wash front and rear glass, check tires, etc. I've even lubed door hinges and stuff.
You could get a lot of service for very little money!
I was one of those guys who, when the bell rang, ran to your vehicle and asked how much gas, wiped your windshield and checked your oil. I waited for the tip but, it very seldom happened.. WARCO STATION in Rock Island ILL ~1955. Ed
We had THREE guys running to your car at Texaco in the late 60's. Each of us had a wad of cash for change and we would check under the hood, wash front and rear glass, check tires, etc. I've even lubed door hinges and stuff.
You could get a lot of service for very little money!
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