just wondering if a tire is max @ 44 lb, and say you put 38.5 lb in it. as it gets heated-up on the road, generally how many lb's does it increase?
also what is your opinion..... what should you run in a tire with a max 44lb pressure. I drive a 99 seville sts.... I'm looking for naturally, tire life, but yet want the car to handle to its potential. I drive mainly highway, and drive as fast as i can get away with. i do understand the more air you put in the tire, the harder the ride, versis low air and soft ride. i have ran with 40lb and thought the car handled well, though a little stiff. will i get better tire life at 40lb, and as they heat up will it excede the max air pressure?
thanks guys
rickyd

 

When the tire companies post max pressure, they are aware of the fact that as you dirve the pressure will increase, so you don't have to worry about putting max pressure in cold tires. I was going to post in my own words, but decided to post the following so that everyone could check out their own situation. Rather long but interesting.











Maximum Load
A tire's maximum load is the most weight the tire is designed to carry. Since a tire's load carrying capacity is related to the tire's size and how much inflation pressure is actually used, maximum loads are rated with the tire inflated to an industry assigned inflation pressure.
Additionally, load ranges are used to separate tires that share the same physical size, but differ in strength due to their internal construction. "Higher" load ranges are used to identify tires that have a stronger internal construction, and therefore can hold more air pressure and carry more weight.
Each load range has a assigned air pressure identified in pounds per square inch (psi) at which the tire's maximum load is rated. Listed below are the air pressures at which maximum load is rated for popular P-metric and LT tires:



Tire Load Ranges

Inflation Pressure Assigned
For "Maximum Load" Ratings

P-metric

Standard Load
(SL)
35 psi

Extra Load
(XL)
41 psi

Light Truck

Load Range C
(LRC)
50 psi

Load Range D
(LRD)
65 psi

Load Range E
(LRE)
80 psi
P-metric tires used on passenger cars and station wagons are rated to carry 100% of the load indicated on the tire's sidewall (or listed for the tire in industry load/inflation charts). However, if the same P-metric tires are used on light trucks, (pickup trucks and sport utility vehicles for example), their carrying capacity is reduced to 91% of the load indicated on the tire's sidewall. This reduction in load results in causing light truck vehicle manufacturers to select proportionately larger P-metric sized tires for their vehicles to help offset the forces and loads resulting from a light truck's higher center of gravity and increased possibility of being occasionally "overloaded."
For example, P235/75R15 P-metric sized, standard load tires used on cars and light trucks would be rated to carry the following maximum loads at 35 psi:



Cars
Full Value
2028 lbs.

Light Trucks
9% Reduced Value
1845 lbs.
Additionally, while a tire's maximum load is the most weight the tire is designed to carry, its load carrying capacity at lower inflation pressures is proportional to how much inflation pressure is used. For example, P235/75R15 P-metric sized, standard load (SL) and extra load (XL) tires used on cars would be rated to carry the following loads at the inflation pressures indicated:



Air Pressure (psi)
20
23
26
29
32
35
38
41

P235/75R15 SL
1543
1635
1753
1852
1940
2028





P235/75R15 XL
1543
1635
1753
1852
1940
2028
2105
2183
Note: 35 psi is the assigned "maximum load" pressure for standard load tires and 41 psi is the assigned "maximum load" pressure for extra load tires.
The above chart correctly shows that an extra load tire is not rated to carry any more load than a standard load tire when both are inflated to the same pressure (up to the standard load tire's "maximum load" pressure of 35 psi). This is because a tire's load capacity is a function of its size (which determines the size of the "air chamber"), its construction (which determines how much pressure can be held) and the actual air pressure used (which determines how many air molecules are forced inside the chamber). All tires with equivalent physical dimensions carry equivalent loads (until they reach their maximum load pressure).
The tire's maximum load is indicated in relatively small sized print branded near the tire's bead (adjacent to the wheel) indicating the appropriate value. Because tires are global products, their maximum load capacity is branded on the tire in kilograms (kg) and pounds (lb.). These values can also be found in the industry's tire load & inflation charts.
NOTE: P-metric and Euro-metric sized tires' "maximum load" inflation pressure may be, and often are, different that the tire's "maximum inflation pressure".

Maximum Inflation Pressure
A tire's maximum inflation pressure is the highest "cold" inflation pressure that the tire is designed to contain. However the tire's maximum inflation pressure should only be used when called for on the vehicle's tire placard or in the vehicle's owners manual. It is also important to remember that the vehicle's recommended tire inflation pressure is always to be measured and set when the tire is "cold". Cold conditions are defined as early in the morning before the day's ambient temperature, sun's radiant heat or the heat generated while driving have caused the tire pressure to temporarily increase.
For the reasons indicated above, It is also normal to experience "hot" tire pressures that are up to 5 to 6 psi above the tire's recommended "cold" pressure during the day if the vehicle is parked in the sun or has been extensively driven. Therefore, if the vehicle's recommended "cold" inflation pressures correspond with the tire's maximum inflation pressure, it will often appear that too much tire pressure is present. However, this extra "hot" tire pressure is temporary and should NOT be bled off to return the tire pressure to within the maximum inflation pressure value branded on the tire. If the "cold" tire pressure was correctly set initially, the temporary "hot" tire pressure will have returned to the tire's maximum inflation pressure when next measured in "cold" conditions.
A tire's "maximum inflation pressure" may be different that the assigned tire pressure used to rate the tire's "maximum load". For example, while a P-metric sized standard load tire's maximum load is rated at 35 psi, many P-metric sized standard load performance and touring tires are designed to contain up to 44 psi (and are branded on their sidewalls accordingly). This additional range of inflation pressure (in this case, between 36 and 44 psi) has been provided to accommodate any unique handling, high speed and/or rolling resistance requirements determined by the tire and vehicle manufacturers. These unique tire pressures will be identified on the vehicle placard in the vehicle's owner's manual.
The tire's maximum inflation pressure is indicated in relatively small-sized print branded near the tire's bead (adjacent to the wheel) indicating the appropriate value. Because tires are global products, their maximum inflation pressure is branded on the tire in kilopascals (kPa) and pounds per square inch (psi). These values can also be found in the industry's tire load & inflation charts.
Tread Depth
Tread depth is a vertical measurement between the top of the tread rubber to the bottom of the tire's deepest grooves. In the United States, tread depth is measured in 32nds of an inch. Because it is difficult to accurately measure tread depth with a ruler, tread depth is best measured with a tire tread depth gauge. When tires have neared the end of their life, a U.S. Lincoln penny can also be used to confirm the tire's tread depth. If Lincoln's entire head is visible, the tire is worn to approximately 2/32" and is considered legally worn out in most States.
Average new tires used on cars typically start with 10/32" to 11/32" of original tread depth. Dedicated winter tires and light truck tires typically are deeper (for light truck tires, how much deeper depends on the tire's tread type…Highway Rib, Highway All Season, Off Road All Terrain or Off Road Maximum Traction).
As mentioned above, tires are legally "worn out" In most States when they reach 2/32" of remaining tread depth. For example, a typical tire that starts with 10/32" of original tread depth has only 8/32" of useable tread depth. Its useable tread depth is calculated by subtracting a worn out tire's 2/32" from the new tire's original depth of 10/32". The final 2/32" of a tire's tread depth isn't part of the equation when it comes to calculating tread depth percentages because the tire is already legally worn out with just 2/32" of remaining tread depth.
Useable tread depth is calculated by subtracting 2/32" from the tires new tread depth. Then usable tread depth is compared to remaining tread depth in order to calculate tread wear percentages. For example, a tire that started with 10/32" of original tread depth and has worn off 4/32" (down to 6/32" of remaining tread depth) is 50% worn[align=center]
10/32" original tread depth
-2/32" legally worn out tread depth
8/32" of useable tread depth.
8/32" useable tread depth
-4/32" measured tread depth worn away
4/32" of remaining tread depth (50% of 8/32")[/align]A tire that starts with 10/32" of original tread depth has 12.5% wear for every 1/32" that is worn away, and a tire that starts with 12/32" " of original tread depth, has 10% wear for every 1/32" that is worn away, etc.
Rim Width Range
Because tires have flexible sidewalls, a single tire size will fit on a variety of rim widths. A tire's rim width range identifies the narrowest to the widest rim widths that the tire is designed to fit. The width of the rim will influence the width of the tire. A tire mounted on a narrow rim would be "narrower" than if the same size tire was mounted on a wide rim. NOTE: Because the overall diameter of a steel belted radial is determined by the steel belts, there is little, if any, change to the overall diameter of the tire due to differences in rim width.
The industry rule of thumb is that for every 1/2" change in rim width, the tire's section width will correspondingly change by approximately 2/10".
For example: a tire in the P205/60R15 size is measured on a 6.0" wide wheel and this size tire has an approved rim width range from 5.5" to 7.5" wide. The tire has a section width of 8.23" (209mm) when mounted on a 6.0" wide wheel. If that tire were mounted on all of the rims within its range, the tire's approximate section width would change as follows:



Difference from
Measuring Rim
Rim
Width
Approximate Tire
section width

0.5" narrower
5.5"
8.03"

Measuring Rim
6.0"
8.23"

0.5" wider
6.5"
8.43"

1.0" wider
7.0"
8.63"

1.5" wider
7.5"
8.83"
Because of the different wheel widths used in the above example, there is a 8/10" projected difference in tire section width when comparing a tire mounted on the narrowest rim to the widest rim within its range. This may affect fenderwell and frame clearances when selecting optional aftermarket wheel and tire packages
Additionally, some vehicle manufacturers and tire companies have permitted rim widths that are not within the tire's original approved rim width range. For example: BMW has combined 235/40R17 sized tires on 17x7.5" rims (which are 0.5" less than the narrowest 8.0" wide rim listed for the size) on certain M3 models; and Chevrolet has combined P255/50R16 sized tires on optional 16x9.5" rims (which are 0.5" wider than the 9.0" wide rim now listed for the size) on certain Corvette models. While these applications have received the approval of the vehicle and tire manufacturers, staying within the approved rim width range helps assure that the tire's internal stresses are within its design parameters.
Measuring Rim Width
The measuring rim width is the industry standardized rim width upon which the tire must be mounted in order to confirm it meets its dimensional targets. Because the width of the rim will influence the width of the tire, a standard rim width for every tire size is assigned and must be used. This standardized measuring rim width allows all of the tires produced around the world to meet the same dimensional standards and therefore, be equivalent with regards to their physical size. The measuring rim width is sometimes referred to as the tire's "design rim width".
The assigned measuring rim width changes with the tire size's section width and with the tire size's aspect ratio. As tire section width increases, the measuring rim width increases proportionately in 1/2" increments. Therefore, relatively narrow wheel widths are assigned for smaller tires while wider wheel widths are assigned for larger tires.



Tire Size

Measuring
Rim Width

P175/75R14
5.0"

P195/75R15
5.5"

P215/75R15
6.0"

P235/75R15
6.5"
Additionally, relatively "narrow" measuring wheel widths are assigned for taller profile tires (75-series sizes) which graduate in 1/2" increments to the wider wheel widths assigned for lower profile tires (40-series sizes)




Tire Size

Measuring
Rim Width

P225/75R15
6.0"

P225/70R15
6.5"

P225/65R16
6.5"

P225/60R15
6.5"

P225/55R15
7.0"

P225/50R15
7.0"

P225/45R17
7.5"

P225/40R18
8.0"
Section Width
A tire's section width (also called "cross section width") is the measurement of the tire's width from its inner sidewall to its outer sidewall (excluding any protective ribs, decorations or raised letters) at the widest point. This measurement is made without any load placed upon the tire and after the tire has been properly mounted on its industry assigned measuring rim and has been inflated and reset to its test pressure after 24 hours.
Because a tire's section width is influenced by the width of the rim upon which the tire is mounted, the correct industry assigned measuring rim width for the tire size being measured must be used.
The width of a tire mounted on a narrow rim would be "narrower" than if the same tire was mounted on a wide rim. NOTE: because the overall diameter of a steel belted radial is determined by the steel belts, there is little, if any, change to the overall diameter of the tire due to differences in rim width.
The industry rule of thumb is that for every 1/2" change in rim width, the tire's section width will correspondingly change by approximately 2/10".
For example: a tire in the P205/60R15 size is measured on a 6.0" wide wheel and this size tire has an approved rim width range from 5.5" to 7.5" wide. The tire has a section width of 8.23" (209mm) when mounted on a 6.0" wide wheel. If that tire were mounted on all of the rims within its approved range, the tire's approximate section width would change as follows:



Difference from
Measuring Rim
Rim
Width
Approximate Tire
section width

0.5" narrower
5.5"
8.03"

Measuring Rim
6.0"
8.23"

0.5" wider
6.5"
8.43"

1.0" wider
7.0"
8.63"

1.5" wider
7.5"
8.93"
Because of the different wheel widths used in the above example, there is a 9/10" projected difference in tire section width when comparing a tire mounted on the narrowest rim to the widest rim within its range. This may affect fenderwell and frame clearances when selecting optional aftermarket wheel and tire packages
Tread Width
The tread width is the distance between the outer edge and the inner edge of the tread of a new tire. However today's radial tires often feature tread designs that incorporate rounded shoulders and there is no industry standard pertaining to "how much" of the rounded shoulders should be included in the tread width measurement. Because of this, it is difficult to accurately compare the tread width differences of one tire brand to another. Tread width measurements are best used when comparing the various tire sizes or lines manufactured by a single tire manufacturer. Several tire manufacturers have chosen not to publish tread width dimensions.
Overall Diameter
A tire's overall diameter is the outer diameter of the tire measured in the center of the tread. This measurement is made without any load placed upon the tire and after the tire has been properly mounted on its industry assigned measuring rim and has been inflated and reset to its test pressure after 24 hours.
Revolutions Per Mile
The revolutions per mile indicates the number of times the tire revolves while it covers the distance of one mile. Depending on the tire manufacturer, revolutions per mile may be either measured

 

G.A.R.Y. so in your opinion, should one run 44lb pressure if that is what the tire calls for, or is it a matter of personal preferance? also living in Erie Pa. with the snow as bad as anywhere..... i usually run with 32lb for better traction in the winter....do you agree with this? THANKS for all
rickyd

 

Adjust to your preference and driving conditions. Just remember that over inflated tires as well as under inflated
tires effect the life of the tire. Lots of allante guys are letting some air out of their tires for a better ride. My '03 sc430 with run flats was an awful ride, yet my '06 vette with run flats is a great ride just by putting the pressure in that's posted on the door. Good luck, let us know after you experiment how it worked out for you. Thanks.

G.A.R.Y.

 

FELLAS AND OTHERS;;; THE MANUFACTURER OF THE TIRE HAS NO IDEA WHAT APPLICATION WILL BE THE FINAL DESTINATION FOR A SPECIFIC TIRE. HE SIMPLY STATES THE MAXIMUM AIR PRESSURE THE TIRE CAN TOLERATE. HE ALSO STATES THE MAXIMUM LOAD THE TIRE CAN TOLERATE. NOW THIS BEEN SAID , THE AUTO MANUFACTURER HAS SPENT MANY HOURS DETERMINING WHICH TIRE SIZE HE WANTS ON THIS CADILLAC TO PERFORM LIKE A CADILLAC. ALWAYS , ALWAYS LISTEN TO THE MANUFACTURER OF THE AUTO . USE THE INFLATION PRESSURE AND THE TIRE SIZE ON THE PLACARD ON THE DRIVERS DOOR OR IN YOUR OWNERS MANUAL . CADILLAC WANTS YOUR CADILLAC TO PERFORM LIKE A CADILLAC. THE TIRE MANUFACTURER WANTS TO COVER HIS LOWER BEHIND SECTION WHEN HE LISTS THE MAXIMUM TIRE PRESSURE AND LOAD RANGE. HOPE THIS HELPS. I HAVE USED THIS RULE FOR MORE THAN 25 YEARS AND IT STILL RULES TRUE TODAY. ( GOODYEAR TIRE AND RUBBER TRAINING. )

 

ILIKECARS.... yes, and i do run GOODYEARS......that being said....... if i run what the dr jam said, the tire seems to heavy, and it seems to roll more..... so for that reason i've taken the psi up to 40lb.....that seems too hard to me....i have at this point 38.5lb and that satisifesmy ride, and handling needs.........Thank You for your imput. In my life I read alotof books, but usually never went by them...

 

the door jam pressures are the MINIMAL recommended .. for a comfy Cadillac ride. Not necessarily the
best for handling off the expected norm driving or high speed. many top-dogs go by the 1/2 way between the door
jamb (MIN) and the tire MAXIMUM.

I NEVER, NEVER run the minimal press on the door jambs.

I run 34 or 38 psi as a routine on the Allantes. But, if i am to be running mountain roads, she goes to
42 psi that allows her to stick on to the tar mat on those curves - and ABS STOPS. i could care
less about a cushy ride then. my passenger is usually too busy keeping her food down - i'm too busy
keeping her 6 inches inside the tar mat to care about comfy or motion sickness.


HIGH SPEED ? ? ?

- I would never run triple digit speeds, for more than 4 seconds, at anything less
than 90% of the MAX printed on the tire - NEVER.

- i would never run triple digits for ONE SECOND at the door jamb minimum - never.

- Lastly, i would never run triple digits at the tire worn below 70%. That means that my Allante has
been limited on high speed runs for a year, since i wont scrap 60% rubber tires

- i will take them to 30%, then scrap them. When i get the new ones, i always knife the sidewalls of
the old ones to keep the tire store from selling them to some fool that doesnt know better.

- my 4x4 (Stomper) gets new tires at the 50% wear - the rocks and debris can be a killer on thin treads.
Those tires, i do turn in for cash against the new tires. A city cruiser 4x4 can run those fine for a couple
more years and look good. Triple digit rules dont apply - Stomper likes a slower type of excitement.
Here the rules change dramatically - I will drop to 1/2 of the door jamb minimal and will go to 90% of the
MAXIMUM on the tire - all depends on the surface she stomps on and the speed - she does carries a
compressor to adjust press as she goes along.

 

stomper...thanks for grabing me back there..... i too feel a difference that just a pound and a half make in tire pressure..... i do believe it is a matter of your driving habits, and how you want your vehicle to handle, and ride. i also like your ideas on speed, and tire inflation. THANKS
rickyd

 

i grew up among automobile racers, drag strips, airplane pilots, rocket guys, engineers,
nurses, soldiers, crashes of all kinds, hospitals and survival training.

i was taught to not follow the herd and be mowed down with it , to always challenge the rules,
to do my own homework, to bond with your machine, to learn to "feel" your machine, to learn
how your machine works, to break where others had not dared ..

and most important of all ..

to know the absolute limits and TO NEVER travel outside the envelope of absolute maximums
and minimums without extra precautions - these are there for a reason - YOUR SURVIVAL ...

 

stomper...... thats what i meant when i said to ilikecars.....In my life i've read alot of books but never went by them lol........cool