Does anyone know when the PSI standards started?

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TacticalDriver

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I am doing a research on tires dynamics, tire technologies and tire pressure. So far I gathered most of the material/information I need, except the history of the PSI standardization.
Why, when, where and who came up with the idea of affixing the sticker on the driver side (door jamb) that shows the manufacturer recommended PSI on front/rear tires.

What is the methodology, how did they (who's they???) come up with those numbers? 28 PSI on the front / 32 PSI on the rear (for example)
When was the first sticker affixed, by which car manufacturer, what model, what year? Was the methodology renewed over the years? And if yes how and who conducted the tests? Where?

I don't seem to find on line so far any of those information.

Any ideas, theories, literature, links?


Thank you anticipated,


TD
 
Each tire has a load rating and the tire pressure is based off of the amount of load on each tire. Now they do tend to have lower pressure to provide a more comfortable ride. That's why when you look at the door and the tire number on the tire is always higher than what the door says because the tire is based on maximum load for the tire. I dont know who came up with putting a sticker on the door.
 
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Originally Posted By: motor_oil_madman
Each tire has a load rating and the tire pressure is based off of the amount of load on each tire. Now they do tend to have lower pressure to provide a more comfortable ride. That's why when you look at the door and the tire number on the tire is always higher than what the door says because the tire is based on maximum load for the tire. I dont know who came up with putting a sticker on the door.
Thank you for your participation. But that still does not answer my question
 
I suspect that the first stickers were a government regulation that grew out of the original Firestone fiasco - Firestone 500 - in the middle 1970's. I suspect this as I have a 1973 Mercury Capri that has load information but no tire size nor inflation pressure. I used to have a 1976 Ford Econoline that had both tire size and pressure.

At the time (1970's), tire sizing was going from what was called "Super Low Section" tires (82 aspect ratio - they looked like this: 6.95-14) to AlphaNumeric (which looked like this: G78-15, with the aspect ratio delineated in the size.)

Just after this was a transition to radial tires - followed quickly by the sizing system we have now - a mix of metric and inches (215/70R15).

How is it calculated? Both tire engineers and vehicle engineers refer to the tire load tables - a set of tables published by tire standardizing organizations that related load carrying capacity to inflation pressure by tire size.

Tire engineers design tires to those tables - and the vehicle engineers use that table to select tire sizes and inflation pressures that have enough load carrying capacity for the max load of the vehicle. Vehicle engineers would take the worst case by position and select a size / inflation pressure combination for the highest loading by wheel position. Sometimes the front and rear tires would have different inflation pressures - sometimes not, as it depends on what the design standard is for each vehivcle manufacturer. In either case, the vehicle would then be tested at that inflation pressure for both ride and handling characteristics. Spring rates, sway bar size, and shock damping would then be tried and adjusted to get the best combination of ride and handling. In particular, the vehicle engineers would avoid combinations that caused unpredictable behavior - as best they could.

I have documented 3 increases in load carrying capacity of tires over the intervening years. One was the result of the oil embargo on about 1973 - for fuel economy resaons. Another was in the 1980's - and I suspect this was the result of what is sometimes called "tire saturation" - fully loaded tires have non-linear force and moment characteritics when heavily loaded.

And the last increase was the result of the latest Ford/Firestone situation - about 2002 to about 2006.

For Super Low Section tires, the maximum load occurred at 32 psi - same for AlphaNumerics. With the currect system, this is 35 psi (Standard Load tires).

If you take a look at the new cars, I think you will find 2 stickers - one that is strictly tire info (size and pressure) and one that has a bunch of info. This second sticker will have that date the vehicle was manufactured (I think by month/year) as well as some info that is pertinent to tire loading.

The second sticker will have the GVWR (Gross Vehicle Weight rating) - that's the maximum weight the vehicle was designed to be when fully loaded. There will also be GAWR's (Gross Axle Weight Rating) for both the front and rear axles. This is the maximum weight the AXLES were designed to carry. Adding both GAWR's together should result in a value slightly lower than the GVWR - to account for slight differences in the way the vehicle is loaded.

While the tire load carrying capacity is not delineated in either of the stickers, if you go to the tire load tables published by the tire standardizing organizations, the load carrying capacity of the tires should be equal to or greater the GAWR's - and nowadays it is greater.

That's the best I can remember about where the stickers come from and how the values are determined. I hope this is helpful.
 
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Originally Posted By: CapriRacer

The second sticker will have the GVWR (Gross Vehicle Weight rating) - that's the maximum weight the vehicle was designed to be when fully loaded. There will also be GAWR's (Gross Axle Weight Rating) for both the front and rear axles. This is the maximum weight the AXLES were designed to carry. Adding both GAWR's together should result in a value slightly lower than the GVWR - to account for slight differences in the way the vehicle is loaded.


Should that say "Adding both GAWR's together should result in a value slightly *higher* than the GVWR"?
 
Originally Posted By: Carbon
.....Should that say "Adding both GAWR's together should result in a value slightly *higher* than the GVWR"?


Yes - and my excuse is that I hadn't even finished my first cup of coffee when I wrote that.
 
Originally Posted By: bullwinkle
The oldest vehicle I've ever seen a PSI sticker on is my '82 300D-actually on the fuel filler door-anybody seen one older?


Yes, my 81 240D
wink.gif
 
The fact that installation of stickers is old doesn't make the information written on it old...unless it was the information written on the sticker when the car was made...

i.e.last year's car with last year's sticker is correct at time of writing, while an LCD retrofitted with 40 year old information is outdated regardless of currentness of the medium.
 
Shannow,

That made a lot of sense...

I'll reread your post after my second cup of coffee.

LOLz, Jim

PS Could it be that Tire Technology is changing everyday? I mean Radial Tire use is only about 40 years old Right?
 
Originally Posted By: motor_oil_madman
Each tire has a load rating and the tire pressure is based off of the amount of load on each tire. Now they do tend to have lower pressure to provide a more comfortable ride. That's why when you look at the door and the tire number on the tire is always higher than what the door says because the tire is based on maximum load for the tire. I dont know who came up with putting a sticker on the door.


I think it's safe to say the car manufacturers came up with this idea. The sticker may also be inside the fuel filler door. It is in any car manufacturer's best interest to provide guidelines regarding tire pressure for each vehicle. Without such guidelines the car manufacturer would be open to liability suits. With the guidelines in place, if some nut decides to deviate grossly from the recommended specs, the nut is liable for any harm stemming from negligence.
 
Originally Posted By: Volvo_ST1
Originally Posted By: motor_oil_madman
Each tire has a load rating and the tire pressure is based off of the amount of load on each tire. Now they do tend to have lower pressure to provide a more comfortable ride. That's why when you look at the door and the tire number on the tire is always higher than what the door says because the tire is based on maximum load for the tire. I dont know who came up with putting a sticker on the door.


I think it's safe to say the car manufacturers came up with this idea. The sticker may also be inside the fuel filler door. It is in any car manufacturer's best interest to provide guidelines regarding tire pressure for each vehicle. Without such guidelines the car manufacturer would be open to liability suits. With the guidelines in place, if some nut decides to deviate grossly from the recommended specs, the nut is liable for any harm stemming from negligence.


It sounds as though you have a pretty good handle on this topic.

Could you explain what was done in the past, before the MFGs got involved, to determine the proper psi to run in automobile tires.

Thanks, Jim
 
Originally Posted By: AstroTurf
.....Could you explain what was done in the past, before the MFGs got involved, to determine the proper psi to run in automobile tires.

Thanks, Jim


I can.

There NEVER was a time where the vehicle manufacturers were not the final arbitrator. They may have sized the tires such that they exactly matched the pressure where the maximum load carrying capacity occurred - and that might appear that the tire manufacturer was setting the specs, but it was the vehicle manufacturers who selected the appropriate tire size.
 
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