psi question
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Teching In
Joined: Apr 2010
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psi question My car originally came with 245/50zr16 with an inflation rate of 30psi on the door tag. When I bought the car about 3 weeks ago it has 275/40zr17 with a max rating of 51psi on the sidewall, should I run it at 51psi ?
Douchebag On The Tree
Joined: Nov 2009
Posts: 1,268
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From: Indianapolis, IN
Whatever the door tag says. It's based off of vehicle weight. Most passenger cars from 3000-3400lbs will be 30-32 psi. My Buick Rendezvous takes 35psi.
The psi based on vehicle weight is to keep the tire from being under or overinflated on a vehicle to vehicle basis.
The psi based on vehicle weight is to keep the tire from being under or overinflated on a vehicle to vehicle basis.
That could be a disaster. Check your tires on a hot summer day after you have driven it. Heat builds more pressure, you might be rolling around with 55+ psi in them. Not to mention you are probably wearing out the centers of your tires.
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On The Tree
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Tech 99 bird is right on. I dont know where people get the idea to run the psi on the sidewall but...... CRAZY! Sure it will give you better mpg's because you have now shaped youre tire like a donut. You're only riding on the center section of the tire. Less rubber touching the road = less resistance = better mpg. Is it worth the risk of blowing out a tire as the pressure builds up from driving around, wearing out your tires prematurely, or the safety side of it? How well is your car gonna handle when only 20% (?) of the tread is touching the road. I personally dont feel the money you save on gas is worth replacing your tires way before they should be either from a blow out, worn out tread, plus the accident avoidance aspect. Run them at the psi the door tag states. It should give cold psi (cold = after your car has sat for appx an hour or more). Sometimes they even label them at cold psi + the amount of passengers that are in the car.
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Yeah, being in the tire business trust me, you should not inflate the tire to sidewall max PSI. Its a no no. And actually if you look in the door of an SS or WS.6 they recommend 30 psi with 275/40/17's so thats what I've run in the past. Though I've been known to do 32 as well. But I figure if you have that size on the same car with different options you should run what GM says.
I've always run max (sidewall) in all of mine with no problems. I will agree that there could be wear issues that could arise (center wear). I haven't experienced that with mine personally, but have seen it. If you check the pressures and wear regularly, I say run whatever you want, but also being in the tire business, I know most people don't. So I always lean toward higher pressures for mine and my customers. Especially since low air is one of the biggest tire killers via wear problems and overheating.
idk but how can anyone say a tire that is inflated to the max psi is rideing on the center? that just seems rediculous. are you telling me that the tire is in the shape of a v with the weight of the car pushing down on it? thats like saying if you blow up a balloon thats designed to hold your weight is not going to take out the roundness when you put your weight on it. im not sure but if you have a tire on the car that isnt stock shouldnt what it says on the tire take priority over whats on the door sticker? yes you are right the psi will go up to about 55 psi but i keep an eye on that.
idk guys but im sure they didnt design that 51 max psi and not compensate for someone accidently letting it get to 55psi because of some heat. they would be in some deep ****. i have both my vehicles tires at max psi,always have,the wear is great,and never had issues. thats just my opinion.........
idk guys but im sure they didnt design that 51 max psi and not compensate for someone accidently letting it get to 55psi because of some heat. they would be in some deep ****. i have both my vehicles tires at max psi,always have,the wear is great,and never had issues. thats just my opinion.........
Douchebag On The Tree
Joined: Nov 2009
Posts: 1,268
Likes: 4
From: Indianapolis, IN
I've always run max (sidewall) in all of mine with no problems. I will agree that there could be wear issues that could arise (center wear). I haven't experienced that with mine personally, but have seen it. If you check the pressures and wear regularly, I say run whatever you want, but also being in the tire business, I know most people don't. So I always lean toward higher pressures for mine and my customers. Especially since low air is one of the biggest tire killers via wear problems and overheating.
idk but how can anyone say a tire that is inflated to the max psi is rideing on the center? that just seems rediculous. are you telling me that the tire is in the shape of a v with the weight of the car pushing down on it? thats like saying if you blow up a balloon thats designed to hold your weight is not going to take out the roundness when you put your weight on it. im not sure but if you have a tire on the car that isnt stock shouldnt what it says on the tire take priority over whats on the door sticker? yes you are right the psi will go up to about 55 psi but i keep an eye on that.
idk guys but im sure they didnt design that 51 max psi and not compensate for someone accidently letting it get to 55psi because of some heat. they would be in some deep ****. i have both my vehicles tires at max psi,always have,the wear is great,and never had issues. thats just my opinion.........
idk guys but im sure they didnt design that 51 max psi and not compensate for someone accidently letting it get to 55psi because of some heat. they would be in some deep ****. i have both my vehicles tires at max psi,always have,the wear is great,and never had issues. thats just my opinion.........
I run at 34 psi. Try not to let it go below 32 ever.
If you travel at high speeds you need to up the pressure 2 psi per 10 miles per hour about 70 I think. So if you go 100 you would need 36 psi to achieve a great balance of inflation and road contact.
Never would I run at max psi. Never go below 30 minimum.
If you travel at high speeds you need to up the pressure 2 psi per 10 miles per hour about 70 I think. So if you go 100 you would need 36 psi to achieve a great balance of inflation and road contact.
Never would I run at max psi. Never go below 30 minimum.
Douchebag On The Tree
Joined: Nov 2009
Posts: 1,268
Likes: 4
From: Indianapolis, IN
Douchebag On The Tree
Joined: Nov 2009
Posts: 1,268
Likes: 4
From: Indianapolis, IN
idk but how can anyone say a tire that is inflated to the max psi is rideing on the center? that just seems rediculous. are you telling me that the tire is in the shape of a v with the weight of the car pushing down on it? thats like saying if you blow up a balloon thats designed to hold your weight is not going to take out the roundness when you put your weight on it. im not sure but if you have a tire on the car that isnt stock shouldnt what it says on the tire take priority over whats on the door sticker? yes you are right the psi will go up to about 55 psi but i keep an eye on that.
idk guys but im sure they didnt design that 51 max psi and not compensate for someone accidently letting it get to 55psi because of some heat. they would be in some deep ****. i have both my vehicles tires at max psi,always have,the wear is great,and never had issues. thats just my opinion.........
idk guys but im sure they didnt design that 51 max psi and not compensate for someone accidently letting it get to 55psi because of some heat. they would be in some deep ****. i have both my vehicles tires at max psi,always have,the wear is great,and never had issues. thats just my opinion.........
a balloon has no rigidity whatsoever. a tire, on the other had, has a good amount of rigidity based on compound and design. (i have two different types of goodyears on my DD's right now. one set will look obviously low with about 25psi in it, while the other set will only be noticed by someone as **** i am and will read 16psi.) so yes the shape of a tire can vary greatly by the amount of air pressure in it, especially when it's inflated to the completely wrong psi to begin with.
Changing the tires from stock doesn't matter as the car still weighs the same. Hypothetically think about taking the tires off a camaro that were inflated to 32psi. Then take those same tires and mount them on a 3500 diesel truck and inflate to the same 32psi. With much more weight now coming down on the tires they will look underinflated(because they are!).
It's all based on the weight of the vehicle on which the tires are equipped.
The only reason to go with a higher pressure than what the door sticker says is if you are running a much thinner sidewall than stock. And this is done to keep from bending your wheels on potholes.
Now to the statement in bold. You are most likely correct that the tire will hold more than the "max 51psi" and that's because they are protecting themselves from people who don't have a clue.
When you change your oil do you put in how much it calls for? Or do you just keep filling it up until oil runs out your valve covers? Because that would technically be the max you could run before you start busting the seams, so to speak.
rant over. thanks for that. well if you will excuse me im going outside to infate my tires to 51 psi 
just to help here...
a balloon has no rigidity whatsoever. a tire, on the other had, has a good amount of rigidity based on compound and design. (i have two different types of goodyears on my DD's right now. one set will look obviously low with about 25psi in it, while the other set will only be noticed by someone as **** i am and will read 16psi.) so yes the shape of a tire can vary greatly by the amount of air pressure in it, especially when it's inflated to the completely wrong psi to begin with.
Changing the tires from stock doesn't matter as the car still weighs the same. Hypothetically think about taking the tires off a camaro that were inflated to 32psi. Then take those same tires and mount them on a 3500 diesel truck and inflate to the same 32psi. With much more weight now coming down on the tires they will look underinflated(because they are!).
It's all based on the weight of the vehicle on which the tires are equipped.
The only reason to go with a higher pressure than what the door sticker says is if you are running a much thinner sidewall than stock. And this is done to keep from bending your wheels on potholes.
Now to the statement in bold. You are most likely correct that the tire will hold more than the "max 51psi" and that's because they are protecting themselves from people who don't have a clue.
When you change your oil do you put in how much it calls for? Or do you just keep filling it up until oil runs out your valve covers? Because that would technically be the max you could run before you start busting the seams, so to speak.
rant over.
a balloon has no rigidity whatsoever. a tire, on the other had, has a good amount of rigidity based on compound and design. (i have two different types of goodyears on my DD's right now. one set will look obviously low with about 25psi in it, while the other set will only be noticed by someone as **** i am and will read 16psi.) so yes the shape of a tire can vary greatly by the amount of air pressure in it, especially when it's inflated to the completely wrong psi to begin with.
Changing the tires from stock doesn't matter as the car still weighs the same. Hypothetically think about taking the tires off a camaro that were inflated to 32psi. Then take those same tires and mount them on a 3500 diesel truck and inflate to the same 32psi. With much more weight now coming down on the tires they will look underinflated(because they are!).
It's all based on the weight of the vehicle on which the tires are equipped.
The only reason to go with a higher pressure than what the door sticker says is if you are running a much thinner sidewall than stock. And this is done to keep from bending your wheels on potholes.
Now to the statement in bold. You are most likely correct that the tire will hold more than the "max 51psi" and that's because they are protecting themselves from people who don't have a clue.
When you change your oil do you put in how much it calls for? Or do you just keep filling it up until oil runs out your valve covers? Because that would technically be the max you could run before you start busting the seams, so to speak.
rant over. Not trying to start any pissing contest, I agree with a lot of what you are saying, but not quite sure what the little head shake is for. You are completely entitled to your opinions. Air pressure is something that can vary from situation to situation. I don't think there is anything wrong with running as low as 30psi if that suits the situation. I've logged close to a million miles on my vehicles running pressures as stated earlier without problems, maybe that is what has me a little huffy. Air pressure relates DIRECTLY with load. (go ahead read the tire) Max load XXX @ Max Pressure XXXpsi. The folks that engineer the tires are quite aware that tires build heat, which results in increasing pressures so to say protecting themselves from people who don't have a clue is simply wrong. Again, read that sidewall, and placard those pressures are cold.The protecting the rims thing, run a different tire (more sidewall). I do have to change one of my statements though, I know of one tire failure due to overinflation, it was a implement tire with a max press rating of 14 psi. the knucklehead put 85 psi in it, it split the sidewall. Also looking at the placard on the door, under it it states for higher speeds to consult manual for pressure recommendations. Everytime the contact patch is on the ground, the sidewall flexes. Increase the rate and thats alot of flexing which = heat, which is bad for the tires (why you up pressures w/ speed/load). Read that sidewall again, every passenger car tire I've ever seen says "safety warning: serious injury may result from: tire failure due to underinflation/overloading:....."
Sorry for the long post, but I feel better now. Best wishes.
Sorry for the long post, but I feel better now. Best wishes.