What should I go by when inflating my tires? The label on the door or the number on the sidewall? I have always followed the door label unless the tire has a significantly higher max PSI. For example the label says 35 and the tires are also 35 then 35 PSI is all I will put in. Now if the tires are max 44 and the label says 35 I would put 40 PSI. Any issues with that plan? I just never get a consistent answer when I ask people in the tire business.
Tire pressure question...
- Thread starter Run
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Nick1994
$100 site donor 2024
The number on the sidewall are the max the tire can handle, not really safe to drive around in a regular car unloaded at that pressure.
Although I go higher than the sticker in the door jam. Toyota says 29 psi unloaded, 32 psi loaded, I run 36. I don't like it driving around on the sidewalls and it gives me some room if I forget to check the pressure for a month or 2. Spare tire is set to 42. That way I can leave it alone and forget about it for a while. I keep a gauge in my car and would lower the pressure in the spare when mounting though.
Although I go higher than the sticker in the door jam. Toyota says 29 psi unloaded, 32 psi loaded, I run 36. I don't like it driving around on the sidewalls and it gives me some room if I forget to check the pressure for a month or 2. Spare tire is set to 42. That way I can leave it alone and forget about it for a while. I keep a gauge in my car and would lower the pressure in the spare when mounting though.
This has come up multiple times. You always go by the pressure on the car door. The car manufacturer knows what the tire pressure is supposed to be because they designed the car with a specific type of suspension. The tire maker has no idea what kind of car the tire will go on and every manufacturer has their own recommendation. Some manufacturers like to spec a lower air pressure for a smoother ride so it might be ok to add a little extra. On the other hand if you go too high, you may end up with abnormal tire wear.
OVERKILL
$100 Site Donor 2021
The number on the tire is the maximum for the tire. The number on the door jamb is the pressure spec for that car with the tire size indicated. Ergo, you go by the number on the jamb unless you have gone to a different size tire that may require a slight change in pressure to yield the OEM contact patch and handling characteristics.
The spec PSI will be a balance between handling, braking, responsiveness and ride quality/comfort. Some cars will have some bias toward comfort, others toward handling. However running the sidewall pressure considers none of that, as the tire manufacturer, who spec's that pressure, has no idea what vehicle it is being fitted to.
The spec PSI will be a balance between handling, braking, responsiveness and ride quality/comfort. Some cars will have some bias toward comfort, others toward handling. However running the sidewall pressure considers none of that, as the tire manufacturer, who spec's that pressure, has no idea what vehicle it is being fitted to.
As a rule I go 2psi over the door label.
Originally Posted By: Tegger
Originally Posted By: Run
The label on the door
I have a question for you: Why do you suppose the automakers put that label there with tire pressures on it?
Well obviously they recommend that from the factory. However cars wear tires out and the replacements sometimes have different specs. Plus the labels don't always recommend the best pressure. Anyone remember the ford explorer fiasco of the 90s?
Originally Posted By: Run
The label on the door
I have a question for you: Why do you suppose the automakers put that label there with tire pressures on it?
Well obviously they recommend that from the factory. However cars wear tires out and the replacements sometimes have different specs. Plus the labels don't always recommend the best pressure. Anyone remember the ford explorer fiasco of the 90s?
Pressure recommended on door is a good thing to follow. Its put for optimum balance of handling and mpg and ride comfort. I would only go 1 or 2 over door but currently just running what door states. I used to run 35 psi but noticed decrease in traction so decided it wasnt worth the mpg savings.
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Originally Posted By: Run
Originally Posted By: Tegger
Originally Posted By: Run
The label on the door
I have a question for you: Why do you suppose the automakers put that label there with tire pressures on it?
Well obviously they recommend that from the factory. However cars wear tires out and the replacements sometimes have different specs. Plus the labels don't always recommend the best pressure. Anyone remember the ford explorer fiasco of the 90s?
This is a classical logical fallacy. That's the recommended pressure assuming you're putting the correct sized tire on the car. Many tire dealers won't put the wrong size/speed rating on a car due to legal liability. Auto makers are supposed to put the correct pressure on the side of the door. Just because one didn't for other reasons due to trying to achieve a softer ride, doesn't mean that they're all wrong now. Firestone also made defective tires, the combination of the two were fatal for some people, especially when their tires were low and the temperature was hot. Absent that, follow the recommendation of the automaker, the tire maker has even less info than the car maker.
Originally Posted By: Tegger
Originally Posted By: Run
The label on the door
I have a question for you: Why do you suppose the automakers put that label there with tire pressures on it?
Well obviously they recommend that from the factory. However cars wear tires out and the replacements sometimes have different specs. Plus the labels don't always recommend the best pressure. Anyone remember the ford explorer fiasco of the 90s?
This is a classical logical fallacy. That's the recommended pressure assuming you're putting the correct sized tire on the car. Many tire dealers won't put the wrong size/speed rating on a car due to legal liability. Auto makers are supposed to put the correct pressure on the side of the door. Just because one didn't for other reasons due to trying to achieve a softer ride, doesn't mean that they're all wrong now. Firestone also made defective tires, the combination of the two were fatal for some people, especially when their tires were low and the temperature was hot. Absent that, follow the recommendation of the automaker, the tire maker has even less info than the car maker.
Originally Posted By: Tegger
Originally Posted By: Run
The label on the door
I have a question for you: Why do you suppose the automakers put that label there with tire pressures on it?
Because the govt. says they have to.
Smoky
Originally Posted By: Run
The label on the door
I have a question for you: Why do you suppose the automakers put that label there with tire pressures on it?
Because the govt. says they have to.
Smoky
Originally Posted By: Smoky14
Originally Posted By: Tegger
I have a question for you: Why do you suppose the automakers put that label there with tire pressures on it?
Because the govt. says they have to.
True, but why do automakers choose the numbers they choose? The government doesn't mandate specific pressure numbers.
Originally Posted By: Tegger
I have a question for you: Why do you suppose the automakers put that label there with tire pressures on it?
Because the govt. says they have to.
True, but why do automakers choose the numbers they choose? The government doesn't mandate specific pressure numbers.
Automakers choose the pressure they choose based on the weight of the vehicle and the specified tire load rating (97, 99, 101, etc)
Before the Ford/Firestone debacle they would put the recommended pressures per size for unloaded (two people, small bag) and loaded (4 people, full trunk.)
After the Ford/Firestone thing automakers in the US were required to list only the pressure reccomended for the highest load the vehicle would apply to the tires. (max vehicle weight) Federally mandated TPMS is also a result of the legislation. Look up the TREAD Act.
Vehicles sold ROW (Rest Of World) still have the dual-reccomended pressure placard on the door.
Example 1, W12 LWB Phaeton US:
Example 2, W12 LWB Phaeton ROW:
Before the Ford/Firestone debacle they would put the recommended pressures per size for unloaded (two people, small bag) and loaded (4 people, full trunk.)
After the Ford/Firestone thing automakers in the US were required to list only the pressure reccomended for the highest load the vehicle would apply to the tires. (max vehicle weight) Federally mandated TPMS is also a result of the legislation. Look up the TREAD Act.
Vehicles sold ROW (Rest Of World) still have the dual-reccomended pressure placard on the door.
Example 1, W12 LWB Phaeton US:
Example 2, W12 LWB Phaeton ROW:
Originally Posted By: rooflessVW
....... Before the Ford/Firestone debacle they would put the recommended pressures per size for unloaded (two people, small bag) and loaded (4 people, full trunk.)
After the Ford/Firestone thing automakers in the US were required to list only the pressure reccomended for the highest load the vehicle would apply to the tires. (max vehicle weight) .......
Ah ...... Mmmmmmm ...... Not exactly.
The requirement has always been that the pressure / tire size combination listed on the vehicle tire placard (regardless of vehicle type) had to be able to carry the max load the tire would experience. That meant that the GAWR's and the GVW were real and equal to or less than load carrying capacity of the tires.
What changed was the vehicle manufacturers adding reserve (unused) capacity into the specification for tires for SUV's and pickups That is, they went to a larger size (load wise). (Passenger cars had been this way for many years!).
....... Before the Ford/Firestone debacle they would put the recommended pressures per size for unloaded (two people, small bag) and loaded (4 people, full trunk.)
After the Ford/Firestone thing automakers in the US were required to list only the pressure reccomended for the highest load the vehicle would apply to the tires. (max vehicle weight) .......
Ah ...... Mmmmmmm ...... Not exactly.
The requirement has always been that the pressure / tire size combination listed on the vehicle tire placard (regardless of vehicle type) had to be able to carry the max load the tire would experience. That meant that the GAWR's and the GVW were real and equal to or less than load carrying capacity of the tires.
What changed was the vehicle manufacturers adding reserve (unused) capacity into the specification for tires for SUV's and pickups That is, they went to a larger size (load wise). (Passenger cars had been this way for many years!).
Originally Posted By: CapriRacer
The requirement has always been that the pressure / tire size combination listed on the vehicle tire placard (regardless of vehicle type) had to be able to carry the max load the tire would experience. That meant that the GAWR's and the GVW were real and equal to or less than load carrying capacity of the tires.
What changed was the vehicle manufacturers adding reserve (unused) capacity into the specification for tires for SUV's and pickups That is, they went to a larger size (load wise). (Passenger cars had been this way for many years!).
In other words... follow the sticker, not the number on the tire. Just like the automaker tells you to in the Owner Manual, which I'm sure everyone has read.
The requirement has always been that the pressure / tire size combination listed on the vehicle tire placard (regardless of vehicle type) had to be able to carry the max load the tire would experience. That meant that the GAWR's and the GVW were real and equal to or less than load carrying capacity of the tires.
What changed was the vehicle manufacturers adding reserve (unused) capacity into the specification for tires for SUV's and pickups That is, they went to a larger size (load wise). (Passenger cars had been this way for many years!).
In other words... follow the sticker, not the number on the tire. Just like the automaker tells you to in the Owner Manual, which I'm sure everyone has read.
It really is vehicle dependent. My 2500 pickup, the OEM recommended is 60 front 70 rear on the door jam, but it also states that is at max gross on the axles. When empty, there is no way I am running those pressures. I typically run 55 psi all the way around for empty or light loaded stuff. Those are E rated tires. Running the lower pressures when empty, the traction and handling is far better, tread wear better and more even, less wheel skip on bumps, and a slight up tick on mpg because the anti slip electronics are not having to micro manage all those bump events. And ride is significantly improved.
My commercial trucks, the tire OEM's are nice enough to provide load range charts to show proper inflation for the tires. Even at my max gross on my semi truck, the recommended pressures are considerably lower than the max rating on the sidewall. I typically average around 225,000 miles on steer tires and over 400,000 on drive tires. So the tire folks much know what they are talking about. But they will not provide that same information to auto/pickup owners. They always punt to the OEM, which is stupid, as the auto/pickup OEM does not design and make tires.
The TPMS has a cow over my running the lower tire pressures on the 2500 tires. I just dismiss it in the DIC and ignore the light.
My commercial trucks, the tire OEM's are nice enough to provide load range charts to show proper inflation for the tires. Even at my max gross on my semi truck, the recommended pressures are considerably lower than the max rating on the sidewall. I typically average around 225,000 miles on steer tires and over 400,000 on drive tires. So the tire folks much know what they are talking about. But they will not provide that same information to auto/pickup owners. They always punt to the OEM, which is stupid, as the auto/pickup OEM does not design and make tires.
The TPMS has a cow over my running the lower tire pressures on the 2500 tires. I just dismiss it in the DIC and ignore the light.
OVERKILL
$100 Site Donor 2021
Originally Posted By: rooflessVW
Automakers choose the pressure they choose based on the weight of the vehicle and the specified tire load rating (97, 99, 101, etc)
Before the Ford/Firestone debacle they would put the recommended pressures per size for unloaded (two people, small bag) and loaded (4 people, full trunk.)
After the Ford/Firestone thing automakers in the US were required to list only the pressure reccomended for the highest load the vehicle would apply to the tires. (max vehicle weight) Federally mandated TPMS is also a result of the legislation. Look up the TREAD Act.
Vehicles sold ROW (Rest Of World) still have the dual-reccomended pressure placard on the door.
I believe many vehicles show both pressures. This is from my former M5:
Automakers choose the pressure they choose based on the weight of the vehicle and the specified tire load rating (97, 99, 101, etc)
Before the Ford/Firestone debacle they would put the recommended pressures per size for unloaded (two people, small bag) and loaded (4 people, full trunk.)
After the Ford/Firestone thing automakers in the US were required to list only the pressure reccomended for the highest load the vehicle would apply to the tires. (max vehicle weight) Federally mandated TPMS is also a result of the legislation. Look up the TREAD Act.
Vehicles sold ROW (Rest Of World) still have the dual-reccomended pressure placard on the door.
I believe many vehicles show both pressures. This is from my former M5:
Originally Posted By: OVERKILL
I believe many vehicles show both pressures. This is from my former M5:
[image deleted]
I think you will find that the only vehicles that list 2 pressures on the vehicle tire placard are older German manufacturers - BMW, VW, etc. - with the possible exception of Dodge/Ram trucks.
I believe many vehicles show both pressures. This is from my former M5:
[image deleted]
I think you will find that the only vehicles that list 2 pressures on the vehicle tire placard are older German manufacturers - BMW, VW, etc. - with the possible exception of Dodge/Ram trucks.
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OVERKILL
$100 Site Donor 2021
Originally Posted By: CapriRacer
Originally Posted By: OVERKILL
I believe many vehicles show both pressures. This is from my former M5:
[image deleted]
I think you will find that the only vehicles that list 2 pressures on the vehicle tire placard are older German manufacturers - BMW, VW, etc. - with the possible exception of Dodge/Ram trucks.
Might the RAM trucks do it as a carry-over from Mercedes or is there a different reason?
Originally Posted By: OVERKILL
I believe many vehicles show both pressures. This is from my former M5:
[image deleted]
I think you will find that the only vehicles that list 2 pressures on the vehicle tire placard are older German manufacturers - BMW, VW, etc. - with the possible exception of Dodge/Ram trucks.
Might the RAM trucks do it as a carry-over from Mercedes or is there a different reason?
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