Tire Pressure vs. FE vs. Safety
#21
07-03-2008, 06:57 PM
Re: Tire Pressure vs. FE vs. Safety
Tim,
My information comes from many sites on the web. FAA, NASA, NHRA, NASCAR, Consumer Reports, Our Military...they all have contributed to what I have learned. Unfortunately I never contemplated having to debate using nitrogen so I did not make notes of references over the past few months. My suggestion is that we agree to disagree. You won't use nitrogen and when we get our FEH we will. All I ask is that unless you don't bash it as snake oil without proof.
Have a great one.
Blind Mike
TLM
My information comes from many sites on the web. FAA, NASA, NHRA, NASCAR, Consumer Reports, Our Military...they all have contributed to what I have learned. Unfortunately I never contemplated having to debate using nitrogen so I did not make notes of references over the past few months. My suggestion is that we agree to disagree. You won't use nitrogen and when we get our FEH we will. All I ask is that unless you don't bash it as snake oil without proof.
Have a great one.
Blind Mike
TLM
For the convenience of those interested, would you please cite a page that has this information. When I've done my research, I can only find evidence of reduced leakage.
#22
07-03-2008, 08:27 PM
Re: Tire Pressure vs. FE vs. Safety
ideal gas law
PV=nRT
where
P is the absolute pressure (SI unit: pascal)
V is the volume (SI unit: cubic metre)
n is the amount of substance (loosely number of moles of gas)
R is the ideal gas constant (SI: 8.3145 J/(mol K))
T is the thermodynamic temperature (SI unit: kelvin).
(The law works with any consistent set of units, provided that the temperature scale starts at absolute zero, and the appropriate gas constant is used.)
Considering the absolute gas law as above, it should be clear that the differences in pressure will be miniscule with the same change in temperature. The only variable would be n, the number of moles of gas. Comparing 100% nitrogen with room air, approximately 78% nitrogen, 21% oxygen, and a very small amount of water vapor, the difference in number of moles of gas total would be marginally different, thus no significant difference in pressure. The presence of oxygen may lead to increased oxidation of the rubber inside the tire, but I am not aware that this is amount of oxidation is significant. phil
PV=nRT
where
P is the absolute pressure (SI unit: pascal)
V is the volume (SI unit: cubic metre)
n is the amount of substance (loosely number of moles of gas)
R is the ideal gas constant (SI: 8.3145 J/(mol K))
T is the thermodynamic temperature (SI unit: kelvin).
(The law works with any consistent set of units, provided that the temperature scale starts at absolute zero, and the appropriate gas constant is used.)
Considering the absolute gas law as above, it should be clear that the differences in pressure will be miniscule with the same change in temperature. The only variable would be n, the number of moles of gas. Comparing 100% nitrogen with room air, approximately 78% nitrogen, 21% oxygen, and a very small amount of water vapor, the difference in number of moles of gas total would be marginally different, thus no significant difference in pressure. The presence of oxygen may lead to increased oxidation of the rubber inside the tire, but I am not aware that this is amount of oxidation is significant. phil
#23
07-05-2008, 04:13 PM
Hybrid and Ethanol Expert
Join Date: Mar 2005
Location: All over the Central U.S.
Posts: 3,616
Re: Tire Pressure vs. FE vs. Safety
To the OP, I have run my tires at 44psi or a tad higher from 8000 on the odometer to the current 66,000 on the odometer.
I still have about 4.5mm to 5mm of tread left on my original tires after running my tires at an average ~45psi for 2.5 years.
They really decrease rolling resistance by a large degree compared to 35psi.
The distance I can coast without gas is lengthend.
I get better MPG than 99.9% of folks out there.
I beat EPA MPG even in winter time.
I will also confirm that the Highway Patrol in California runs the air pressure at 50psi in the Crown Victorica police cars, even though the manufacturer says 35psi is "recommended".
Higher air pressure is desired for increased safety and performance in all driving conditions, except icy, or in deep sand ( beaches ).
Nitrogen is not helpful for street cars, and mindful owners who check tire pressure.
I was recently listening to "Road Dog" station on Sirius, the trucker channel, and the topic of the day was tires. The guest on the show was a representative from Firestone / Bridgestone.
He said in tests done with their company, in co-operation with the Dept. of Transportation, extensive testing shows truck ( & trailer ) tires filled with Nitrogen leak 1.5% less pressure than tires with plain air. Also pointing out that for the single owner/operator Nitrogen was not worth the time, effort, or cost. But for a major fleet with 1000's of trucks ( UPS? FedEx? ) that 1.5% pressure could add up to significant fuel savings fleet-wide.
I have personally spoken to mechanics who work in the NASCAR industry. Since I have person to person knowlegde, I guess I am my own reference. They use compressed Nitrogen in the race tires, but not for the reasons commonly assumed. Nitrogen is used because it is sold DRY. The Nascar Pit Crew uses the same Nitrogen Cylinders ( at really high pressure with regulators ) to run the air tools, and fill the tires. The air needs to be dry to protect the tools, not the tires. Also, the compressed cyliders do not require any electricity to operate, do not create any sparks, can be used right next to an open fuel bottle, as Nitrigen does not support combustion in case of a fire.
My brother is a certifed aircraft mechanic. He has worked on both commercial and private aircraft. They use Nitrogen to fill airplane tires because A) IT IS DRY. Commercial Aircraft tires are exposed to nearly -65'F temperatures at high altitude. Commercial tires contain a large VOLUME. If there was water in the "air" this would condense and freeze at the low point in the tire during flight. The tire would be out of balance upon landing when the tire needs to go from zero RPM to a few thousand RPM in a fraction of a second. This wobble could cause damage, and/or make the plane difficult to control. My brother said dry air is acceptible, but it is harder to "make" dry air. B) Nitrogen does not support combustion, and will actually act as a fire extinguisher, if needed. Try that with compressed air, and you fan the flames! Nitrogen cylinders can be used to top off tires right next to a re-fueling truck. C) Nitrogen bottles are highly portable - They do not require electricty or gasoline to operate - and they are easy to move around where needed. D) Nitrogen bottles come at very high pressure. This fills large volume tires quickly. A Nitrogen bottle will fill an airplane tire in seconds. You can't do that with a 100 psi standard air-compressor. They DO NOT use Nitrogen because it holds pressure better.
They do NOT use Nitrogen in small, private aircraft tires. There is NO Federal mandate to use Nitogen in any aircraft tire.
-John
I still have about 4.5mm to 5mm of tread left on my original tires after running my tires at an average ~45psi for 2.5 years.
They really decrease rolling resistance by a large degree compared to 35psi.
The distance I can coast without gas is lengthend.
I get better MPG than 99.9% of folks out there.
I beat EPA MPG even in winter time.
I will also confirm that the Highway Patrol in California runs the air pressure at 50psi in the Crown Victorica police cars, even though the manufacturer says 35psi is "recommended".
Higher air pressure is desired for increased safety and performance in all driving conditions, except icy, or in deep sand ( beaches ).
Nitrogen is not helpful for street cars, and mindful owners who check tire pressure.
I was recently listening to "Road Dog" station on Sirius, the trucker channel, and the topic of the day was tires. The guest on the show was a representative from Firestone / Bridgestone.
He said in tests done with their company, in co-operation with the Dept. of Transportation, extensive testing shows truck ( & trailer ) tires filled with Nitrogen leak 1.5% less pressure than tires with plain air. Also pointing out that for the single owner/operator Nitrogen was not worth the time, effort, or cost. But for a major fleet with 1000's of trucks ( UPS? FedEx? ) that 1.5% pressure could add up to significant fuel savings fleet-wide.
I have personally spoken to mechanics who work in the NASCAR industry. Since I have person to person knowlegde, I guess I am my own reference. They use compressed Nitrogen in the race tires, but not for the reasons commonly assumed. Nitrogen is used because it is sold DRY. The Nascar Pit Crew uses the same Nitrogen Cylinders ( at really high pressure with regulators ) to run the air tools, and fill the tires. The air needs to be dry to protect the tools, not the tires. Also, the compressed cyliders do not require any electricity to operate, do not create any sparks, can be used right next to an open fuel bottle, as Nitrigen does not support combustion in case of a fire.
My brother is a certifed aircraft mechanic. He has worked on both commercial and private aircraft. They use Nitrogen to fill airplane tires because A) IT IS DRY. Commercial Aircraft tires are exposed to nearly -65'F temperatures at high altitude. Commercial tires contain a large VOLUME. If there was water in the "air" this would condense and freeze at the low point in the tire during flight. The tire would be out of balance upon landing when the tire needs to go from zero RPM to a few thousand RPM in a fraction of a second. This wobble could cause damage, and/or make the plane difficult to control. My brother said dry air is acceptible, but it is harder to "make" dry air. B) Nitrogen does not support combustion, and will actually act as a fire extinguisher, if needed. Try that with compressed air, and you fan the flames! Nitrogen cylinders can be used to top off tires right next to a re-fueling truck. C) Nitrogen bottles are highly portable - They do not require electricty or gasoline to operate - and they are easy to move around where needed. D) Nitrogen bottles come at very high pressure. This fills large volume tires quickly. A Nitrogen bottle will fill an airplane tire in seconds. You can't do that with a 100 psi standard air-compressor. They DO NOT use Nitrogen because it holds pressure better.
They do NOT use Nitrogen in small, private aircraft tires. There is NO Federal mandate to use Nitogen in any aircraft tire.
-John
#24
07-05-2008, 04:59 PM
Active Enthusiast
Join Date: Jun 2008
Location: New Jersey. Land of high auto insurance and pollution.
Posts: 127
Re: Tire Pressure vs. FE vs. Safety
To the OP, I have run my tires at 44psi or a tad higher from 8000 on the odometer to the current 66,000 on the odometer.
I still have about 4.5mm to 5mm of tread left on my original tires after running my tires at an average ~45psi for 2.5 years.
They really decrease rolling resistance by a large degree compared to 35psi.
The distance I can coast without gas is lengthend.
I get better MPG than 99.9% of folks out there.
I beat EPA MPG even in winter time.
I will also confirm that the Highway Patrol in California runs the air pressure at 50psi in the Crown Victorica police cars, even though the manufacturer says 35psi is "recommended".
Higher air pressure is desired for increased safety and performance in all driving conditions, except icy, or in deep sand ( beaches ).
Nitrogen is not helpful for street cars, and mindful owners who check tire pressure.
I was recently listening to "Road Dog" station on Sirius, the trucker channel, and the topic of the day was tires. The guest on the show was a representative from Firestone / Bridgestone.
He said in tests done with their company, in co-operation with the Dept. of Transportation, extensive testing shows truck ( & trailer ) tires filled with Nitrogen leak 1.5% less pressure than tires with plain air. Also pointing out that for the single owner/operator Nitrogen was not worth the time, effort, or cost. But for a major fleet with 1000's of trucks ( UPS? FedEx? ) that 1.5% pressure could add up to significant fuel savings fleet-wide.
I have personally spoken to mechanics who work in the NASCAR industry. Since I have person to person knowlegde, I guess I am my own reference. They use compressed Nitrogen in the race tires, but not for the reasons commonly assumed. Nitrogen is used because it is sold DRY. The Nascar Pit Crew uses the same Nitrogen Cylinders ( at really high pressure with regulators ) to run the air tools, and fill the tires. The air needs to be dry to protect the tools, not the tires. Also, the compressed cyliders do not require any electricity to operate, do not create any sparks, can be used right next to an open fuel bottle, as Nitrigen does not support combustion in case of a fire.
My brother is a certifed aircraft mechanic. He has worked on both commercial and private aircraft. They use Nitrogen to fill airplane tires because A) IT IS DRY. Commercial Aircraft tires are exposed to nearly -65'F temperatures at high altitude. Commercial tires contain a large VOLUME. If there was water in the "air" this would condense and freeze at the low point in the tire during flight. The tire would be out of balance upon landing when the tire needs to go from zero RPM to a few thousand RPM in a fraction of a second. This wobble could cause damage, and/or make the plane difficult to control. My brother said dry air is acceptible, but it is harder to "make" dry air. B) Nitrogen does not support combustion, and will actually act as a fire extinguisher, if needed. Try that with compressed air, and you fan the flames! Nitrogen cylinders can be used to top off tires right next to a re-fueling truck. C) Nitrogen bottles are highly portable - They do not require electricty or gasoline to operate - and they are easy to move around where needed. D) Nitrogen bottles come at very high pressure. This fills large volume tires quickly. A Nitrogen bottle will fill an airplane tire in seconds. You can't do that with a 100 psi standard air-compressor. They DO NOT use Nitrogen because it holds pressure better.
They do NOT use Nitrogen in small, private aircraft tires. There is NO Federal mandate to use Nitogen in any aircraft tire.
-John
I still have about 4.5mm to 5mm of tread left on my original tires after running my tires at an average ~45psi for 2.5 years.
They really decrease rolling resistance by a large degree compared to 35psi.
The distance I can coast without gas is lengthend.
I get better MPG than 99.9% of folks out there.
I beat EPA MPG even in winter time.
I will also confirm that the Highway Patrol in California runs the air pressure at 50psi in the Crown Victorica police cars, even though the manufacturer says 35psi is "recommended".
Higher air pressure is desired for increased safety and performance in all driving conditions, except icy, or in deep sand ( beaches ).
Nitrogen is not helpful for street cars, and mindful owners who check tire pressure.
I was recently listening to "Road Dog" station on Sirius, the trucker channel, and the topic of the day was tires. The guest on the show was a representative from Firestone / Bridgestone.
He said in tests done with their company, in co-operation with the Dept. of Transportation, extensive testing shows truck ( & trailer ) tires filled with Nitrogen leak 1.5% less pressure than tires with plain air. Also pointing out that for the single owner/operator Nitrogen was not worth the time, effort, or cost. But for a major fleet with 1000's of trucks ( UPS? FedEx? ) that 1.5% pressure could add up to significant fuel savings fleet-wide.
I have personally spoken to mechanics who work in the NASCAR industry. Since I have person to person knowlegde, I guess I am my own reference. They use compressed Nitrogen in the race tires, but not for the reasons commonly assumed. Nitrogen is used because it is sold DRY. The Nascar Pit Crew uses the same Nitrogen Cylinders ( at really high pressure with regulators ) to run the air tools, and fill the tires. The air needs to be dry to protect the tools, not the tires. Also, the compressed cyliders do not require any electricity to operate, do not create any sparks, can be used right next to an open fuel bottle, as Nitrigen does not support combustion in case of a fire.
My brother is a certifed aircraft mechanic. He has worked on both commercial and private aircraft. They use Nitrogen to fill airplane tires because A) IT IS DRY. Commercial Aircraft tires are exposed to nearly -65'F temperatures at high altitude. Commercial tires contain a large VOLUME. If there was water in the "air" this would condense and freeze at the low point in the tire during flight. The tire would be out of balance upon landing when the tire needs to go from zero RPM to a few thousand RPM in a fraction of a second. This wobble could cause damage, and/or make the plane difficult to control. My brother said dry air is acceptible, but it is harder to "make" dry air. B) Nitrogen does not support combustion, and will actually act as a fire extinguisher, if needed. Try that with compressed air, and you fan the flames! Nitrogen cylinders can be used to top off tires right next to a re-fueling truck. C) Nitrogen bottles are highly portable - They do not require electricty or gasoline to operate - and they are easy to move around where needed. D) Nitrogen bottles come at very high pressure. This fills large volume tires quickly. A Nitrogen bottle will fill an airplane tire in seconds. You can't do that with a 100 psi standard air-compressor. They DO NOT use Nitrogen because it holds pressure better.
They do NOT use Nitrogen in small, private aircraft tires. There is NO Federal mandate to use Nitogen in any aircraft tire.
-John1. You are absolutely correct...the FAA has no mandate about nitrogen, its only a recomendation. Then again, I never claimed there was a mandate.
2."tires filled with Nitrogen leak 1.5% less pressure than tires with plain air." Interesting because according to the Consumer Reports study, car and light truck tires lost 3.5psi(air) & 2.2psi(nitrogen) Thats more than 30% less pressure loss according to my math.
3."Nitrogen is not helpful for street cars, and mindful owners who check tire pressure" Since nitrogen use in light trucks and passenger cars has not had any "real world" long term use studies how can you say it would not be helpful in either improving FE or reducing wear/ageing of tires? Look up the Baldwin report from Ford to check on ageing of tires.
4."condense and freeze at the low point in the tire during flight" What about after sitting overnight in the driveway during the winter? Granted there is probably less than an ounce of water in each tire but out-of-ballance even for a short time until the tire warms up will still be out-of-ballance.
Listen, I am not saying nitrogen is a perfect sollution. Nor am I saying it is for everyone. In my situation with my wife being the primary driver of the FEH the ability to not worry about her tire pressure every month is helpful and the reduced ageing/wear on the tires may be cost effective. Its $39.00 to fill all 4 tires and have them topped off quarterly for 2 years at a station down the road.
As I said before, lets agree to disagree and leave it at that. Don't bash a product that hasn't even had a chance to prove itself in the consumer market.
Sincerely,
Blind Mike & Michelle
TwoLostMinds
#25
07-06-2008, 12:24 AM
Hybrid and Ethanol Expert
Join Date: Mar 2005
Location: All over the Central U.S.
Posts: 3,616
Re: Tire Pressure vs. FE vs. Safety
Just a couple things....
2."tires filled with Nitrogen leak 1.5% less pressure than tires with plain air." Interesting because according to the Consumer Reports study, car and light truck tires lost 3.5psi(air) & 2.2psi(nitrogen) Thats more than 30% less pressure loss according to my math.
How many cars did CR test? Was it 2? VERY small sample size. I believe the trucking study used 100's of trucks, with 18 tires per truck. Without having the exact numbers, it was a MUCH larger sample. With a different style of tire, I suppose... but I also suppose the rubber used (for molecule migration) was very similer to your car, and mine. Why are people so focused on molecule migration through the tire, when 99.9% of all pressure leaks are from going AROUND the tire at the rim interface, or at the valve stem?P.S. didn't you know CR gets paid to say what is in its best interest? CR is not a public service company, they are a private for-profit company, and many people who have trusted them in the past, no longer do.
3."Nitrogen is not helpful for street cars, and mindful owners who check tire pressure" Since nitrogen use in light trucks and passenger cars has not had any "real world" long term use studies how can you say it would not be helpful in either improving FE or reducing wear/ageing of tires?
Common sense, plus years of university science classes tell me so.
4."condense and freeze at the low point in the tire during flight" What about after sitting overnight in the driveway during the winter? Granted there is probably less than an ounce of water in each tire but out-of-ballance even for a short time until the tire warms up will still be out-of-ballance.
Both the lower volume, and the fact your car tires start slowly from a stop, and have lower top speeds ( usually ) makes this a minor concern for cars.
Its $39.00 to fill all 4 tires and have them topped off quarterly for 2 years at a station down the road.
Whoa! That is WAY expensive! And you still need to check them and top them off??? Just like air?
I thought we were talking $1 or $2 extra per tire! It's not worth it to most folks at $2 a tire. You are losing money at $2. At $1, you'll probably come out even. Geez... I only pay $49 for tires with 60,000 mile treadwear!!! Just trying to be helpful and inform the public of some commonplace "rip-offs". I'm not trying to tell you what to do. -John
2."tires filled with Nitrogen leak 1.5% less pressure than tires with plain air." Interesting because according to the Consumer Reports study, car and light truck tires lost 3.5psi(air) & 2.2psi(nitrogen) Thats more than 30% less pressure loss according to my math.
How many cars did CR test? Was it 2? VERY small sample size. I believe the trucking study used 100's of trucks, with 18 tires per truck. Without having the exact numbers, it was a MUCH larger sample. With a different style of tire, I suppose... but I also suppose the rubber used (for molecule migration) was very similer to your car, and mine. Why are people so focused on molecule migration through the tire, when 99.9% of all pressure leaks are from going AROUND the tire at the rim interface, or at the valve stem?P.S. didn't you know CR gets paid to say what is in its best interest? CR is not a public service company, they are a private for-profit company, and many people who have trusted them in the past, no longer do.
3."Nitrogen is not helpful for street cars, and mindful owners who check tire pressure" Since nitrogen use in light trucks and passenger cars has not had any "real world" long term use studies how can you say it would not be helpful in either improving FE or reducing wear/ageing of tires?
Common sense, plus years of university science classes tell me so.
4."condense and freeze at the low point in the tire during flight" What about after sitting overnight in the driveway during the winter? Granted there is probably less than an ounce of water in each tire but out-of-ballance even for a short time until the tire warms up will still be out-of-ballance.
Both the lower volume, and the fact your car tires start slowly from a stop, and have lower top speeds ( usually ) makes this a minor concern for cars.
Its $39.00 to fill all 4 tires and have them topped off quarterly for 2 years at a station down the road.
Whoa! That is WAY expensive! And you still need to check them and top them off??? Just like air?
I thought we were talking $1 or $2 extra per tire! It's not worth it to most folks at $2 a tire. You are losing money at $2. At $1, you'll probably come out even. Geez... I only pay $49 for tires with 60,000 mile treadwear!!! Just trying to be helpful and inform the public of some commonplace "rip-offs". I'm not trying to tell you what to do. -John
#26
07-06-2008, 03:41 AM
Re: Tire Pressure vs. FE vs. Safety
From the Consumer Report site--subscription--
http://discussions.consumerreports.org/n/pfx/forum.aspx?tsn=11&nav=messages&webtag=cr-tiretalk&tid=1410
message 1410.8 from the CR Expert
We are still testing, but I can tell you that we are not seeing remarkable differences in tires filled with nitrogen vs. air.
There was no final report from CR on tires filled with nitrogen vs air. There is no way to know of the sample size.
http://discussions.consumerreports.org/n/pfx/forum.aspx?tsn=11&nav=messages&webtag=cr-tiretalk&tid=1410
message 1410.8 from the CR Expert
We are still testing, but I can tell you that we are not seeing remarkable differences in tires filled with nitrogen vs. air.
There was no final report from CR on tires filled with nitrogen vs air. There is no way to know of the sample size.
#27
07-06-2008, 10:16 AM
Active Enthusiast
Join Date: Jun 2008
Location: New Jersey. Land of high auto insurance and pollution.
Posts: 127
Re: Tire Pressure vs. FE vs. Safety
Anyway..back to tire pressure. John, your keeping yours around 44-45psi with little additional wear to reduce rolling resistance. What are others currently running? Could those running higher pressures create a graph showing an PSI to FE improvment curve?
I was also reading about how hysteresis/heat is the main cause effecting tire rolling resistance. So if I understand correctly increasing the PSI will reduce the size of the contact patch of the tire and reduce hysteresis thus reducing rolling resistance. Am I correct in this line of thinking?
Sincerely,
Blind Mike & Michelle
TwoLostMinds
I was also reading about how hysteresis/heat is the main cause effecting tire rolling resistance. So if I understand correctly increasing the PSI will reduce the size of the contact patch of the tire and reduce hysteresis thus reducing rolling resistance. Am I correct in this line of thinking?
Sincerely,
Blind Mike & Michelle
TwoLostMinds
#28
07-06-2008, 10:46 AM
Hybrid and Ethanol Expert
Join Date: Mar 2005
Location: All over the Central U.S.
Posts: 3,616
Re: Tire Pressure vs. FE vs. Safety
Most people, most websites, and most "experts" agree, that adding 10 psi over 35 will give you 2-3 MPG extra. I have done this in all three of my cars, and have seen about a 3 MPG gain in all 3 cars... 2 hybrids, one a 1988 Dodge Truck.
The curve is not liner. You do get diminishing returns above 45 psi.
Lets say at 35 psi you get 30 MPG ave.
At 45 psi you can expect 33 MPG ( +3 ).
At 55 psi you can expect 35 MPG ( +5 ).
At 65 psi you can expect 36 MPG ( +6 ).
Above that, and you are asking for disaster.
At 45 psi and under, you will see only slightly greater wear in the center of the tire.
It took me 40,000 miles to notice the center tread was thinner than the edges.
It took me 40,000 miles to get the center tread at 4.5mm when the edge was 5mm.
At 35 psi, lets say for argument sake the contact patch with the ground is 25 sq/in per tire, or 100 sq/in per vehicle. Contact patch is most important for stopping on ice/snow/sand.
Smaller contact patch is better for stopping in rain/water.
Smaller contact patch has little effect on stopping power on dry pavement.
At 45 psi your contact will be 78 sq/in.
At 55 psi your contact will be 64 sq/in.
at 65 psi your contact will be 54 sq/in.
I use 45 psi in non snowy months.
I use 36-38 psi in snowy conditions.
-John
The curve is not liner. You do get diminishing returns above 45 psi.
Lets say at 35 psi you get 30 MPG ave.
At 45 psi you can expect 33 MPG ( +3 ).
At 55 psi you can expect 35 MPG ( +5 ).
At 65 psi you can expect 36 MPG ( +6 ).
Above that, and you are asking for disaster.
At 45 psi and under, you will see only slightly greater wear in the center of the tire.
It took me 40,000 miles to notice the center tread was thinner than the edges.
It took me 40,000 miles to get the center tread at 4.5mm when the edge was 5mm.
At 35 psi, lets say for argument sake the contact patch with the ground is 25 sq/in per tire, or 100 sq/in per vehicle. Contact patch is most important for stopping on ice/snow/sand.
Smaller contact patch is better for stopping in rain/water.
Smaller contact patch has little effect on stopping power on dry pavement.
At 45 psi your contact will be 78 sq/in.
At 55 psi your contact will be 64 sq/in.
at 65 psi your contact will be 54 sq/in.
I use 45 psi in non snowy months.
I use 36-38 psi in snowy conditions.
-John
#29
07-15-2008, 10:28 AM
Re: Tire Pressure vs. FE vs. Safety
Costco fills with Nitrogen for FREE!!!
well if you buy the tires first...
http://tires.costco.com/TireInformat...ostCoAdvantage
"Upon the service of your tires our Michelin Certified Tire Technicians will also install new rubber valve stems (Note TPMS valve stems and accessories will be an additional charge). Additionally, we inflate your tires with nitrogen, not compressed air. Nitrogen retains tire pressure better over time than compressed air, which can positively impact the life of your tires, as well as the fuel economy of your vehicle. We offer this service FREE OF CHARGE."
sound like a good deal.... right?
well if you buy the tires first...
http://tires.costco.com/TireInformat...ostCoAdvantage
"Upon the service of your tires our Michelin Certified Tire Technicians will also install new rubber valve stems (Note TPMS valve stems and accessories will be an additional charge). Additionally, we inflate your tires with nitrogen, not compressed air. Nitrogen retains tire pressure better over time than compressed air, which can positively impact the life of your tires, as well as the fuel economy of your vehicle. We offer this service FREE OF CHARGE."
sound like a good deal.... right?
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RoyalF
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