Maybe I'll try 40 next time I pump them up.
how do you know what psi to run
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I treat pressure on door placard as minimum and on tire sidewall as maximum, I usually have 2-8 PSI above door placard and I like a little higher PSI(about 2 PSI) on front than rear.
I start with the placard, then adjust accordingly. Some tires with firm sidewall I'd stay near placard, some with soft sidewall I'd go up 2-3 PSI, or until the chalk mark across the trend on the tire is worn evenly, which is usually also around 2-3 PSI above placard.
+1, this is the best reply regarding the education opportunity here.
One thing to consider, tire makes and car makers are not making recommendations for the same result.
The car maker wants you to be happy with the car. The tire maker wants you to be happy with the tire. It is possible each makes a recommendation in their best interests and it may not be equal to what the other recommends.
Originally Posted By: KitaCam
First of all, well done Chevy for noticing this apparent contradiction of information....said as a former teacher...some say always a teacher...
I always expected my students to notice this type of "expertise" offered and taught them to "question authority" of the authors when their own experience taught them otherwise...
This is not to say that I taught students to say that such authoritativeness was automatically wrong and that they were automatically right, but taught them to ASK WHY there was this conflict between their knowledge and the text knowledge....
You could bring in this thread to class and declare the authors idiots...but...that would only bring in more anecdotal experience to support one view over another...but experience is not knowledge unless supported by research...
You can say you've done some of YOUR OWN research of knowledgable car owners and since nearly all disagree with the tire manufacturers and some who modify the car maker's recommendation, you want to know WHY....
[even though everything I know about tire pressure supports what you've read here...and answer why you should follow car manufacturers and not tire manufacturers....and answer the quesstions I pose below, ask you prof....]
.....you should 1st ask your prof. WHY the tire manufacturers would tell car owners such general information that is so different from car manufacturers.
.....you should ask why the tire manufacturers recommend the PSI settings that they do...what is THEIR PURPOSE for such a variance from car makers' PSI settings...
....you should ask your prof what is the impact of different PSI settings on tire wear and function, and on the car's performance.
THAT is the role of a good student...to ask why...
One thing to consider, tire makes and car makers are not making recommendations for the same result.
The car maker wants you to be happy with the car. The tire maker wants you to be happy with the tire. It is possible each makes a recommendation in their best interests and it may not be equal to what the other recommends.
Originally Posted By: KitaCam
First of all, well done Chevy for noticing this apparent contradiction of information....said as a former teacher...some say always a teacher...
I always expected my students to notice this type of "expertise" offered and taught them to "question authority" of the authors when their own experience taught them otherwise...
This is not to say that I taught students to say that such authoritativeness was automatically wrong and that they were automatically right, but taught them to ASK WHY there was this conflict between their knowledge and the text knowledge....
You could bring in this thread to class and declare the authors idiots...but...that would only bring in more anecdotal experience to support one view over another...but experience is not knowledge unless supported by research...
You can say you've done some of YOUR OWN research of knowledgable car owners and since nearly all disagree with the tire manufacturers and some who modify the car maker's recommendation, you want to know WHY....
[even though everything I know about tire pressure supports what you've read here...and answer why you should follow car manufacturers and not tire manufacturers....and answer the quesstions I pose below, ask you prof....]
.....you should 1st ask your prof. WHY the tire manufacturers would tell car owners such general information that is so different from car manufacturers.
.....you should ask why the tire manufacturers recommend the PSI settings that they do...what is THEIR PURPOSE for such a variance from car makers' PSI settings...
....you should ask your prof what is the impact of different PSI settings on tire wear and function, and on the car's performance.
THAT is the role of a good student...to ask why...
I have a friend with a Lexus IS300, and he was complaining about a bumpy ride. I told him it was his skinny sidewalls. 215/45/18 tire. Then i checked the pressures, i didnt get an accurate reading because my gauge stops at 50psi... Needless to say i cold-set them all at 38psi, which is 5psi over spec.
Im surprised the tires didnt blow off the wheel when he hit a bump!
Im surprised the tires didnt blow off the wheel when he hit a bump!
You have to be very careful here.
The tire will either have a mximum pressure listed on the sidewall of the tire - OR - it show the relationship of maximum load vs inflation pressure. These are NOT equivalent statements.
For example: Some passenger car tires will have imprinted on the sideall a maximum inflation pressure of 51 psi. This is NOT an indication of the relationship of pressure with load carrying capacity.
When a vehicle manufacturer puts the vehicle tire placard on his vehicle, he is SPECIFYING the inflation pressure he wants used. This pressure affects the ride, handling (response to steering input), grip (wet, dry, and snow traction), fuel economy, etc. If you use a higher pressure, then the size of the contact patch gets smaller and that has an affect of the grip - and unless you test the amount of grip at the higher pressure, you don't know what that is.
The vehicle manufacturer has thoroughly tested his vehicles at the specified pressure. A tire manufacturer CAN NOT test on all the vehicles being produced - BUT - he is sure the vehicle manufacturer has - and while a particular tire may have different characteristics, all the important (read this as "safety related" characteristics) are cataloged by the tire manufacturer.
Hint: When tire manufacturers conduct on-vehicle tire tests, they use the placard inflation pressure.
Allow me to give you an example: Some Mazda Miata's specify a pressure of 26 psi - but can be equipped with tires with a maximum inflation pressure of 51 psi. At that pressure, the vehicle is going to be "bouncy" because the springs on the vehicle were set for a tire with a lower spring rate.
The tire will either have a mximum pressure listed on the sidewall of the tire - OR - it show the relationship of maximum load vs inflation pressure. These are NOT equivalent statements.
For example: Some passenger car tires will have imprinted on the sideall a maximum inflation pressure of 51 psi. This is NOT an indication of the relationship of pressure with load carrying capacity.
When a vehicle manufacturer puts the vehicle tire placard on his vehicle, he is SPECIFYING the inflation pressure he wants used. This pressure affects the ride, handling (response to steering input), grip (wet, dry, and snow traction), fuel economy, etc. If you use a higher pressure, then the size of the contact patch gets smaller and that has an affect of the grip - and unless you test the amount of grip at the higher pressure, you don't know what that is.
The vehicle manufacturer has thoroughly tested his vehicles at the specified pressure. A tire manufacturer CAN NOT test on all the vehicles being produced - BUT - he is sure the vehicle manufacturer has - and while a particular tire may have different characteristics, all the important (read this as "safety related" characteristics) are cataloged by the tire manufacturer.
Hint: When tire manufacturers conduct on-vehicle tire tests, they use the placard inflation pressure.
Allow me to give you an example: Some Mazda Miata's specify a pressure of 26 psi - but can be equipped with tires with a maximum inflation pressure of 51 psi. At that pressure, the vehicle is going to be "bouncy" because the springs on the vehicle were set for a tire with a lower spring rate.
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I typically run 5 over the PSI that's listed on the vehicle's door jam. That usually gives me the best compromise between ride, handling, fuel economy, and tire wear/longevity. I say typically because some tires don't work well with the additional 5 PSI. If I add the extra 5 PSI to the tires on my Corolla it rides as though the tires are solid rubber....very rough riding...so I have to keep them right at the pressure listed on the door....I also believe running a pressure that's 2-4 PSI under the tire's max pressure is too high....
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have to match it to your car and F/R also your gauge could be off but when you find the right psi you can stick w/ it
anything over 36 is pushing it in most cars. you can decrease traction by going over the optimum psi for any tire
anything over 36 is pushing it in most cars. you can decrease traction by going over the optimum psi for any tire
1. Yes....gauges may not be accurate...must be double checked at point of purchase and occasionally thereafter to ensure it has remained accurate.
2.I think many would agree that door-jam label recommendations are for more for comfort than for high performance...hence...
3.Increasing pressure is an attempt to "firm up" the ride...this is in part accomplished (and felt a lot when cornering) because the sidewall is bolstered/firmed up with more air...
4.As has been said, increasing pressure reduces the tread's "foot-print" and traction that initially may increase with the pressure can reach and exceed the point of diminishing returns and begins to REDUCE.
5.The relationship between tire pressure and performance varies with the tire and the car and driving dynamics and the driver's ability to control them
...for some drivers, increasing tire pressure by as little as 2psi over door-jam recommendations can push their driving abilities to and beyond their limit.
Increasing PSI must be done with utmost care and for safety's sake done in small increments.
2.I think many would agree that door-jam label recommendations are for more for comfort than for high performance...hence...
3.Increasing pressure is an attempt to "firm up" the ride...this is in part accomplished (and felt a lot when cornering) because the sidewall is bolstered/firmed up with more air...
4.As has been said, increasing pressure reduces the tread's "foot-print" and traction that initially may increase with the pressure can reach and exceed the point of diminishing returns and begins to REDUCE.
5.The relationship between tire pressure and performance varies with the tire and the car and driving dynamics and the driver's ability to control them
...for some drivers, increasing tire pressure by as little as 2psi over door-jam recommendations can push their driving abilities to and beyond their limit.
Increasing PSI must be done with utmost care and for safety's sake done in small increments.
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OVERKILL
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Originally Posted By: Kuato
No. Inflating your tires to their max pressure will NOT destroy the suspension and will not knock your teeth around. However the ride is firmer.
I can't agree with your wear estimate, and have found the opposite to be true -- for years I ran the placarded pressure and usually ended up with worn outer edges of tires and not much wear in the center.
Did you ever rotate them?
Quote:
Can we all agree that a properly inflated tire will show even wear across the entire tread? If so, then choosing an arbitrary number listed on the door panel or anywhere else isn't correct -- everyone's saying use this or that number but I didn't see any real world testing. You've got to play around with it to get the proper pressure for your vehicle.
The numbers on the placard are not arbitrary. They are the tested and engineered for figures specified by the manufacturer to give the best handling, wear, and ride comfort for the vehicle in question equipped with tires of the same size and load rating as what is also listed.
Quote:
For my last 8 vehicles (the 2 in the sig, 2008 Nissan Versa, 2000 Grand Cherokee, 2004 Dodge truck, 1986 Mercury, 1996 Jeep Wrangler, 1993 Ford Crown Vic) I have found that inflating the tires to their maximum value provided even wear across the tread. For some of the vehicles,there was excessive wear on the edges. For NO vehicle was there more wear on the center of the tire.
Well my anecdote to counter yours are simply that I run the placard pressure on all my vehicles and the tires wear evenly as well. I am running stock size and load rating tires.
Quote:
In each case, the inflation pressure was a good bit higher than the placard on the door frame. Manufacturers often placard a tire pressure that give the best ride...a firm ride isn't what Mr. Old Guy wants in his car, he wants it cushy and may not care about tire wear.
You honestly believe that this is all the manufacturer shoots for, ride comfort? That can be tuned with suspension, it isn't just about the tires. CapriRacer has touched on this as well, I suggest reading his posts as he works in the industry and is very knowledgeable on this subject.
Quote:
For me, the history I have over the last 300,000 miles of driving the vehicles listed above shows pretty conclusively that a higher pressure gives more even wear. Finally, in those miles I experienced exactly ZERO suspension issues.
My history over very similar mileage running placard pressure has shown the same results. Guess we are both right
No. Inflating your tires to their max pressure will NOT destroy the suspension and will not knock your teeth around. However the ride is firmer.
I can't agree with your wear estimate, and have found the opposite to be true -- for years I ran the placarded pressure and usually ended up with worn outer edges of tires and not much wear in the center.
Did you ever rotate them?
Quote:
Can we all agree that a properly inflated tire will show even wear across the entire tread? If so, then choosing an arbitrary number listed on the door panel or anywhere else isn't correct -- everyone's saying use this or that number but I didn't see any real world testing. You've got to play around with it to get the proper pressure for your vehicle.
The numbers on the placard are not arbitrary. They are the tested and engineered for figures specified by the manufacturer to give the best handling, wear, and ride comfort for the vehicle in question equipped with tires of the same size and load rating as what is also listed.
Quote:
For my last 8 vehicles (the 2 in the sig, 2008 Nissan Versa, 2000 Grand Cherokee, 2004 Dodge truck, 1986 Mercury, 1996 Jeep Wrangler, 1993 Ford Crown Vic) I have found that inflating the tires to their maximum value provided even wear across the tread. For some of the vehicles,there was excessive wear on the edges. For NO vehicle was there more wear on the center of the tire.
Well my anecdote to counter yours are simply that I run the placard pressure on all my vehicles and the tires wear evenly as well. I am running stock size and load rating tires.
Quote:
In each case, the inflation pressure was a good bit higher than the placard on the door frame. Manufacturers often placard a tire pressure that give the best ride...a firm ride isn't what Mr. Old Guy wants in his car, he wants it cushy and may not care about tire wear.
You honestly believe that this is all the manufacturer shoots for, ride comfort? That can be tuned with suspension, it isn't just about the tires. CapriRacer has touched on this as well, I suggest reading his posts as he works in the industry and is very knowledgeable on this subject.
Quote:
For me, the history I have over the last 300,000 miles of driving the vehicles listed above shows pretty conclusively that a higher pressure gives more even wear. Finally, in those miles I experienced exactly ZERO suspension issues.
My history over very similar mileage running placard pressure has shown the same results. Guess we are both right
OVERKILL
$100 Site Donor 2021
From Michelin:
http://www.michelin.ca/faq-detail.page?c...3C11527A9804A10
Quote:
When installing a different size than the original equipment tire, all vehicle manufacturer specifications must be maintained. The replacement tire should be inflated to provide the same load capability of the original tire size at the manufacturer’s recommended pressure.
Please contact one of our Consumer Care agents to determine the correct pressure for the optional tire size that you are installing or visit your local tire retailer for assistance.
http://www.michelin.ca/faq-detail.page?c...8D0146011C1A150
Quote:
The vehicle manufacturer selects the size and type of tires for their vehicles. They perform the necessary testing to establish the vehicles’ optimized operating tire inflation pressures which can be found on the vehicle placard (located on the inside of the driver's door) and in the vehicle owners’ manual.
If the tires on your vehicle are the same size as the original equipment tire, inflate them to the pressures indicated on the placard.
http://www.michelin.ca/faq-detail.page?c...3C11527A9804A10
Quote:
When installing a different size than the original equipment tire, all vehicle manufacturer specifications must be maintained. The replacement tire should be inflated to provide the same load capability of the original tire size at the manufacturer’s recommended pressure.
Please contact one of our Consumer Care agents to determine the correct pressure for the optional tire size that you are installing or visit your local tire retailer for assistance.
http://www.michelin.ca/faq-detail.page?c...8D0146011C1A150
Quote:
The vehicle manufacturer selects the size and type of tires for their vehicles. They perform the necessary testing to establish the vehicles’ optimized operating tire inflation pressures which can be found on the vehicle placard (located on the inside of the driver's door) and in the vehicle owners’ manual.
If the tires on your vehicle are the same size as the original equipment tire, inflate them to the pressures indicated on the placard.
If you really want to get tire pressures right, you get a tire pyrometer and measure temperatures. The temperatures will tell you whether you're over-inflated or under-inflated as well as whether camber needs adjusting.
Or you could just run what the vehicle manufacturer said to run and feel pretty confident that's going to be in the ballpark.
robert
Or you could just run what the vehicle manufacturer said to run and feel pretty confident that's going to be in the ballpark.
robert
This time of year, I generally put about ~ 3 psi over what's indicated on the placard, just so I don't need to top them off as frequently.
Then again, I'm not sure how accurate consumer-grade pressure gauges really are. I might still be within the margin of error.
Then again, I'm not sure how accurate consumer-grade pressure gauges really are. I might still be within the margin of error.
Originally Posted By: kb01
This time of year, I generally put about ~ 3 psi over what's indicated on the placard, just so I don't need to top them off as frequently.
I do the same, but because the car is in a heated garage, and if it goes outside into say -20 C, the TPMS kicks in.
This time of year, I generally put about ~ 3 psi over what's indicated on the placard, just so I don't need to top them off as frequently.
I do the same, but because the car is in a heated garage, and if it goes outside into say -20 C, the TPMS kicks in.
You need to adjust for expected temp where the car is operated.
Originally Posted By: OVERK1LL
Originally Posted By: Kuato
No. Inflating your tires to their max pressure will NOT destroy the suspension and will not knock your teeth around. However the ride is firmer.
I can't agree with your wear estimate, and have found the opposite to be true -- for years I ran the placarded pressure and usually ended up with worn outer edges of tires and not much wear in the center.
Did you ever rotate them?
Yup, sure did.
Originally Posted By: OVERK1LL
My history over very similar mileage running placard pressure has shown the same results. Guess we are both right
Perhaps we ARE both right. Driving style, weight of the vehicle and WHERE you drive all make a big difference in tire wear.
For example, all highway = less shoulder wear. All city = LOTS of shoulder wear.
Originally Posted By: Kuato
No. Inflating your tires to their max pressure will NOT destroy the suspension and will not knock your teeth around. However the ride is firmer.
I can't agree with your wear estimate, and have found the opposite to be true -- for years I ran the placarded pressure and usually ended up with worn outer edges of tires and not much wear in the center.
Did you ever rotate them?
Yup, sure did.
Originally Posted By: OVERK1LL
My history over very similar mileage running placard pressure has shown the same results. Guess we are both right
Perhaps we ARE both right. Driving style, weight of the vehicle and WHERE you drive all make a big difference in tire wear.
For example, all highway = less shoulder wear. All city = LOTS of shoulder wear.
OVERKILL
$100 Site Donor 2021
Originally Posted By: Kuato
Originally Posted By: OVERK1LL
Originally Posted By: Kuato
No. Inflating your tires to their max pressure will NOT destroy the suspension and will not knock your teeth around. However the ride is firmer.
I can't agree with your wear estimate, and have found the opposite to be true -- for years I ran the placarded pressure and usually ended up with worn outer edges of tires and not much wear in the center.
Did you ever rotate them?
Yup, sure did.
Originally Posted By: OVERK1LL
My history over very similar mileage running placard pressure has shown the same results. Guess we are both right
Perhaps we ARE both right. Driving style, weight of the vehicle and WHERE you drive all make a big difference in tire wear.
For example, all highway = less shoulder wear. All city = LOTS of shoulder wear.
Originally Posted By: OVERK1LL
Originally Posted By: Kuato
No. Inflating your tires to their max pressure will NOT destroy the suspension and will not knock your teeth around. However the ride is firmer.
I can't agree with your wear estimate, and have found the opposite to be true -- for years I ran the placarded pressure and usually ended up with worn outer edges of tires and not much wear in the center.
Did you ever rotate them?
Yup, sure did.
Originally Posted By: OVERK1LL
My history over very similar mileage running placard pressure has shown the same results. Guess we are both right
Perhaps we ARE both right. Driving style, weight of the vehicle and WHERE you drive all make a big difference in tire wear.
For example, all highway = less shoulder wear. All city = LOTS of shoulder wear.
Everyone is right!
Often in this place people throw around info that is totally platform-specific and not relevant to other cars. This tire inflation stuff is no different.
Mfgr's tune suspensions in a variety of different ways, and tire pressures are set to a median number that reflects the "group think" of the engineers in charge. This means that a Lincoln may have a very different focus than a Corvette. One group is looking at NVH and so forth with the highest priorities and another group is more interested in performance. Ford even set tire pressures low on the old Exploders because they knew they were prone to roll over!
Then factor in drivers, tires, roads, etc. and their infinite variations and you can easily see that no single psi can possibly meet everyone's needs or wants.
Often in this place people throw around info that is totally platform-specific and not relevant to other cars. This tire inflation stuff is no different.
Mfgr's tune suspensions in a variety of different ways, and tire pressures are set to a median number that reflects the "group think" of the engineers in charge. This means that a Lincoln may have a very different focus than a Corvette. One group is looking at NVH and so forth with the highest priorities and another group is more interested in performance. Ford even set tire pressures low on the old Exploders because they knew they were prone to roll over!
Then factor in drivers, tires, roads, etc. and their infinite variations and you can easily see that no single psi can possibly meet everyone's needs or wants.
Originally Posted By: chevyboy14
I found out that the reason a lot of firestone tires failed was because people ran than above 10% below the max rating thus effecting the tire with to much heat and ruining the glue atleast that is what I was told ...
Wrong.
The failures were one model of a very mediocre tire from one factory...Firestone's Decatur plant, now closed. Overloading was a critical factor, plus the fact that the Explorer of that model (around model year 2000) was known by Ford to be top heavy. Recommended tire inflation pressure was 26 psi, and the combination of running low tire pressure below 26, plus overloading, plus hot weather, plus the top heavy vehicle killed people. Goodyear original equipment tires run under the same conditions did not fail at the excessive failure rate of the Decatur Firestone tires.
http://www.ce.berkeley.edu/~sanjay/REPORT_WEB_Secure.PDF
http://en.wikipedia.org/wiki/Firestone_and_Ford_tire_controversy
I found out that the reason a lot of firestone tires failed was because people ran than above 10% below the max rating thus effecting the tire with to much heat and ruining the glue atleast that is what I was told ...
Wrong.
The failures were one model of a very mediocre tire from one factory...Firestone's Decatur plant, now closed. Overloading was a critical factor, plus the fact that the Explorer of that model (around model year 2000) was known by Ford to be top heavy. Recommended tire inflation pressure was 26 psi, and the combination of running low tire pressure below 26, plus overloading, plus hot weather, plus the top heavy vehicle killed people. Goodyear original equipment tires run under the same conditions did not fail at the excessive failure rate of the Decatur Firestone tires.
http://www.ce.berkeley.edu/~sanjay/REPORT_WEB_Secure.PDF
http://en.wikipedia.org/wiki/Firestone_and_Ford_tire_controversy
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