I have a 4 door car that requires 30 PSI cold tire pressure. I noticed the front tires were sagging a little so I checked them and the gauge read 38. I also tested it against 2 other gauges a d its accurate. If I lower the cold air pressure to 30 or even 32 those tires are going to be sagging even more. My question is should I just go by what's required and not worry how the tire looks?
Question Regarding Air Pressure
- Thread starter Mark72
- Start date
- Status
Yup, don't worry about the looks. Modern radial tires do look like they're sagging even when the pressure is correct.
Radial tires typically have a slight bulge at normal inflation pressure. They are designed that way, and it is not a sign of under inflation. What you choose to run your tire pressure at is your choice. Don't go lower than the recommended 30 psi, but going higher has some plus's, and some minus's.
PLUS: More responsive handling, slightly better fuel economy.
MINUS: Stiffer ride, maybe less max grip, maybe slightly more centre tread wear.
Experiment a little, and see what works best for your car. What car / tire / tire size ?
PLUS: More responsive handling, slightly better fuel economy.
MINUS: Stiffer ride, maybe less max grip, maybe slightly more centre tread wear.
Experiment a little, and see what works best for your car. What car / tire / tire size ?
Last edited:
If ypu are sure the gauge is accurate, what the manual says is good, as the others have said. That being said, I always try to keep a few extra lbs over spec's in mine. I know it is controversial, but that is what I do.
I run 38 in the front on the Grand Prix, it drives better and the tires last longer.
Does the car have original tire size and O.E. load Rating?
What is the MAX COLD pressure molded into the sidewall?
How will the car be used and loaded?
If OEM rubber, you should be closer to the manufacturer;s cold spec which is around 68 degressF which is NIST STP.
I traditionally use 50deg F for STP on tires.
add a pound to cold spec for every 10 degrees above. So if you are checking them when its 88F add 2 psig to the door placard.
Me, I wouldnt go above 3psig over door placard on OEM rubber.
On the cold side for passenger cars I allow a 1 psig loss - whithout the need to refill - for every 20 deg below STP. This is because the tire will heat up whilst driven on the highway above ambient air temp.
What is the MAX COLD pressure molded into the sidewall?
How will the car be used and loaded?
If OEM rubber, you should be closer to the manufacturer;s cold spec which is around 68 degressF which is NIST STP.
I traditionally use 50deg F for STP on tires.
add a pound to cold spec for every 10 degrees above. So if you are checking them when its 88F add 2 psig to the door placard.
Me, I wouldnt go above 3psig over door placard on OEM rubber.
On the cold side for passenger cars I allow a 1 psig loss - whithout the need to refill - for every 20 deg below STP. This is because the tire will heat up whilst driven on the highway above ambient air temp.
Originally Posted by MCompact
Make sure that your gauge is accurate
How do you do that? Is there a way to accurately test it?
Make sure that your gauge is accurate
How do you do that? Is there a way to accurately test it?
Originally Posted by atikovi
Originally Posted by MCompact
Make sure that your gauge is accurate
How do you do that? Is there a way to accurately test it?
Usually you check against a known good gauge or at least 2-3 other gauges and see if its reasonably close.
Originally Posted by MCompact
Make sure that your gauge is accurate
How do you do that? Is there a way to accurately test it?
Usually you check against a known good gauge or at least 2-3 other gauges and see if its reasonably close.
Sorry but I have to say
With these kind of threads there are usually so many different opinions that it is completely baffling to everyone.
I have always found with my vehicles that a few psi above what is placarded gives me the most even tire wear and longest tire life. How much over was a function of the weight of the vehicle, and the quality of the tire - cheaper tires were more sensitive to excessive wear.
A couple of real life examples - in a 2004 Jeep grand Cherokee, I bought the vehicle with 18,000 miles with tires at exactly placarded pressure. The front tires were worn almost smooth on the inside and outside edges, while the center of the tread was hardly worn at all. The rears were in similar condition so tires had been rotated. It would wash out badly in the rain, so the tires were soon replaced and over the next 80,000 I experienced even wear by running them at a higher pressure and rotating every 10,000 miles.
In a 2013 Ford F1 50, the same was also true - much more wear on the inner and outer edges of the front tires. It benefited from higher psi, and also when towing or hauling a load the owners manual recommended Increasing psi for more load carrying ability.
With these kind of threads there are usually so many different opinions that it is completely baffling to everyone.
I have always found with my vehicles that a few psi above what is placarded gives me the most even tire wear and longest tire life. How much over was a function of the weight of the vehicle, and the quality of the tire - cheaper tires were more sensitive to excessive wear.
A couple of real life examples - in a 2004 Jeep grand Cherokee, I bought the vehicle with 18,000 miles with tires at exactly placarded pressure. The front tires were worn almost smooth on the inside and outside edges, while the center of the tread was hardly worn at all. The rears were in similar condition so tires had been rotated. It would wash out badly in the rain, so the tires were soon replaced and over the next 80,000 I experienced even wear by running them at a higher pressure and rotating every 10,000 miles.
In a 2013 Ford F1 50, the same was also true - much more wear on the inner and outer edges of the front tires. It benefited from higher psi, and also when towing or hauling a load the owners manual recommended Increasing psi for more load carrying ability.
Originally Posted by JLTD
Sorry but I have to say
With these kind of threads there are usually so many different opinions that it is completely baffling to everyone.
I have always found with my vehicles that a few psi above what is placarded gives me the most even tire wear and longest tire life. How much over was a function of the weight of the vehicle, and the quality of the tire - cheaper tires were more sensitive to excessive wear.
A couple of real life examples - in a 2004 Jeep grand Cherokee, I bought the vehicle with 18,000 miles with tires at exactly placarded pressure. The front tires were worn almost smooth on the inside and outside edges, while the center of the tread was hardly worn at all. The rears were in similar condition so tires had been rotated. It would wash out badly in the rain, so the tires were soon replaced and over the next 80,000 I experienced even wear by running them at a higher pressure and rotating every 10,000 miles.
In a 2013 Ford F1 50, the same was also true - much more wear on the inner and outer edges of the front tires. It benefited from higher psi, and also when towing or hauling a load the owners manual recommended Increasing psi for more load carrying ability.
Hi,
Sorry, I thought increasing the pressure would increase centre wear.
Cheers,
Iain.
Sorry but I have to say
With these kind of threads there are usually so many different opinions that it is completely baffling to everyone.
I have always found with my vehicles that a few psi above what is placarded gives me the most even tire wear and longest tire life. How much over was a function of the weight of the vehicle, and the quality of the tire - cheaper tires were more sensitive to excessive wear.
A couple of real life examples - in a 2004 Jeep grand Cherokee, I bought the vehicle with 18,000 miles with tires at exactly placarded pressure. The front tires were worn almost smooth on the inside and outside edges, while the center of the tread was hardly worn at all. The rears were in similar condition so tires had been rotated. It would wash out badly in the rain, so the tires were soon replaced and over the next 80,000 I experienced even wear by running them at a higher pressure and rotating every 10,000 miles.
In a 2013 Ford F1 50, the same was also true - much more wear on the inner and outer edges of the front tires. It benefited from higher psi, and also when towing or hauling a load the owners manual recommended Increasing psi for more load carrying ability.
Hi,
Sorry, I thought increasing the pressure would increase centre wear.
Cheers,
Iain.
Much as above. Everyone I know goes higher than placard.
I'm diligent regarding tire pressure and rotation.
I've been running 36-38 psi on 3 consecutive Volvo V70's since 2002 and I get even wear and long tire life.
Then, when high speed travel is eminent, add the 10%. I bleed that 10% off when I reach my destination.
If that's too much for work for a driver, he'll pay with faster wear.
FYI: If your car is PARKED on slightly uneven ground there's a rolling (as in the filled tire rolls off center) effect which can make tires look horribly soft.
Just another case for working on level ground.
NASTINESS WARNING: People simply using the placard as gospel without considering specifics and unknowns is like people who obey "lifetime transmission fluid" claims by car manufacturers.
Involvement is necessary.
I'm diligent regarding tire pressure and rotation.
I've been running 36-38 psi on 3 consecutive Volvo V70's since 2002 and I get even wear and long tire life.
Then, when high speed travel is eminent, add the 10%. I bleed that 10% off when I reach my destination.
If that's too much for work for a driver, he'll pay with faster wear.
FYI: If your car is PARKED on slightly uneven ground there's a rolling (as in the filled tire rolls off center) effect which can make tires look horribly soft.
Just another case for working on level ground.
NASTINESS WARNING: People simply using the placard as gospel without considering specifics and unknowns is like people who obey "lifetime transmission fluid" claims by car manufacturers.
Involvement is necessary.
Originally Posted by Rand
Originally Posted by atikovi
Originally Posted by MCompact
Make sure that your gauge is accurate
How do you do that? Is there a way to accurately test it?
Usually you check against a known good gauge or at least 2-3 other gauges and see if its reasonably close.
I would assume you are using the known good gauge to begin with, and the 2-3 other gauges could be off too. Aren't there places with testers that you can check? I remember one of the chain parts stores had remote testers in each store and some had torque wrench testers.
Originally Posted by atikovi
Originally Posted by MCompact
Make sure that your gauge is accurate
How do you do that? Is there a way to accurately test it?
Usually you check against a known good gauge or at least 2-3 other gauges and see if its reasonably close.
I would assume you are using the known good gauge to begin with, and the 2-3 other gauges could be off too. Aren't there places with testers that you can check? I remember one of the chain parts stores had remote testers in each store and some had torque wrench testers.
Originally Posted by Kira
Everyone I know goes higher than placard ...
NASTINESS WARNING: People simply using the placard as gospel without considering specifics and unknowns is like people who obey "lifetime transmission fluid" claims by car manufacturers.
Involvement is necessary.
The placard is a good place to start ... the manufacturer has tested the car and tire combination over thousands of miles, and determined the spec'd pressure that works best for THEIR performance criteria.
YOUR performance criteria may be similar, or different ... thus different pressure settings may be appropriate for your individual preferences. It is OK to experiment ... but keep eye on tread wear, and don't go too low if you don't understand max load, or max speed tire requirements, or heat degradation risks etc.
Most cars are either biased towards comfort, or to the tires being able to handle the maximum permissible load ( full load of passengers and luggage) , or the maximum attainable speed ( think Autobahn or racetrack) . Some cars will have a lower set of recommended tire pressures in the owners manual, for light loads or lower speeds.
Everyone I know goes higher than placard ...
NASTINESS WARNING: People simply using the placard as gospel without considering specifics and unknowns is like people who obey "lifetime transmission fluid" claims by car manufacturers.
Involvement is necessary.
The placard is a good place to start ... the manufacturer has tested the car and tire combination over thousands of miles, and determined the spec'd pressure that works best for THEIR performance criteria.
YOUR performance criteria may be similar, or different ... thus different pressure settings may be appropriate for your individual preferences. It is OK to experiment ... but keep eye on tread wear, and don't go too low if you don't understand max load, or max speed tire requirements, or heat degradation risks etc.
Most cars are either biased towards comfort, or to the tires being able to handle the maximum permissible load ( full load of passengers and luggage) , or the maximum attainable speed ( think Autobahn or racetrack) . Some cars will have a lower set of recommended tire pressures in the owners manual, for light loads or lower speeds.
Put your engine and trans in the trunk and see what tires look like they're sagging.
Radials, by design, have a noticeable bulge at bottom.
Trust your gauge.
Originally Posted by Mark72
I have a 4 door car that requires 30 PSI cold tire pressure. I noticed the front tires were sagging a little so I checked them and the gauge read 38. I also tested it against 2 other gauges a d its accurate. If I lower the cold air pressure to 30 or even 32 those tires are going to be sagging even more. My question is should I just go by what's required and not worry how the tire looks?
Radials, by design, have a noticeable bulge at bottom.
Trust your gauge.
Originally Posted by Mark72
I have a 4 door car that requires 30 PSI cold tire pressure. I noticed the front tires were sagging a little so I checked them and the gauge read 38. I also tested it against 2 other gauges a d its accurate. If I lower the cold air pressure to 30 or even 32 those tires are going to be sagging even more. My question is should I just go by what's required and not worry how the tire looks?
Originally Posted by SpitFire6
Originally Posted by JLTD
Sorry but I have to say
With these kind of threads there are usually so many different opinions that it is completely baffling to everyone.
I have always found with my vehicles that a few psi above what is placarded gives me the most even tire wear and longest tire life. How much over was a function of the weight of the vehicle, and the quality of the tire - cheaper tires were more sensitive to excessive wear.
A couple of real life examples - in a 2004 Jeep grand Cherokee, I bought the vehicle with 18,000 miles with tires at exactly placarded pressure. The front tires were worn almost smooth on the inside and outside edges, while the center of the tread was hardly worn at all. The rears were in similar condition so tires had been rotated. It would wash out badly in the rain, so the tires were soon replaced and over the next 80,000 I experienced even wear by running them at a higher pressure and rotating every 10,000 miles.
In a 2013 Ford F1 50, the same was also true - much more wear on the inner and outer edges of the front tires. It benefited from higher psi, and also when towing or hauling a load the owners manual recommended Increasing psi for more load carrying ability.
Hi,
Sorry, I thought increasing the pressure would increase centre wear.
Cheers,
Iain.
It will, but only if you go too high on the pressure.
Originally Posted by JLTD
Sorry but I have to say
With these kind of threads there are usually so many different opinions that it is completely baffling to everyone.
I have always found with my vehicles that a few psi above what is placarded gives me the most even tire wear and longest tire life. How much over was a function of the weight of the vehicle, and the quality of the tire - cheaper tires were more sensitive to excessive wear.
A couple of real life examples - in a 2004 Jeep grand Cherokee, I bought the vehicle with 18,000 miles with tires at exactly placarded pressure. The front tires were worn almost smooth on the inside and outside edges, while the center of the tread was hardly worn at all. The rears were in similar condition so tires had been rotated. It would wash out badly in the rain, so the tires were soon replaced and over the next 80,000 I experienced even wear by running them at a higher pressure and rotating every 10,000 miles.
In a 2013 Ford F1 50, the same was also true - much more wear on the inner and outer edges of the front tires. It benefited from higher psi, and also when towing or hauling a load the owners manual recommended Increasing psi for more load carrying ability.
Hi,
Sorry, I thought increasing the pressure would increase centre wear.
Cheers,
Iain.
It will, but only if you go too high on the pressure.
OVERKILL
$100 Site Donor 2021
Originally Posted by Kira
NASTINESS WARNING: People simply using the placard as gospel without considering specifics and unknowns is like people who obey "lifetime transmission fluid" claims by car manufacturers.
Involvement is necessary.
It's a heck of a lot brighter than folks blindly going by the max pressure spec on the sidewall
At least going by the placard involves using the "right" pressure, as in what was tested and found to be the best fit for the operating intentions of the vehicle under typical conditions. I doubt many have gone to the trouble of testing skidpad, braking...etc performance when deviating from that spec. Of course then there are those rolling around with who knows what pressure, which is why we now have TPMS. It takes all kinds.
NASTINESS WARNING: People simply using the placard as gospel without considering specifics and unknowns is like people who obey "lifetime transmission fluid" claims by car manufacturers.
Involvement is necessary.
It's a heck of a lot brighter than folks blindly going by the max pressure spec on the sidewall
A couple of thoughts:
On FWD cars - and most cars nowadays are - the front tires are much more loaded than the rears, so it is common for the fronts to look "overloaded" if you compare them to the rears, but that's an illusion.
Increasing the inflation pressure TENDS to cause wear in the center of the tread - and decreased pressure TENDS to wear the shoulders. BUT inflation pressure is NOT the strongest influence on evenness of wear. "Spirited" driving or misalignment is a much stronger influence than pressure.
And lastly, it is a fallacy that a tire's wear is EXACTLY right if the pressure is EXACTLY right. Not only are there things that have more influence, not all tires have the best footprint even if properly inflated.
On FWD cars - and most cars nowadays are - the front tires are much more loaded than the rears, so it is common for the fronts to look "overloaded" if you compare them to the rears, but that's an illusion.
Increasing the inflation pressure TENDS to cause wear in the center of the tread - and decreased pressure TENDS to wear the shoulders. BUT inflation pressure is NOT the strongest influence on evenness of wear. "Spirited" driving or misalignment is a much stronger influence than pressure.
And lastly, it is a fallacy that a tire's wear is EXACTLY right if the pressure is EXACTLY right. Not only are there things that have more influence, not all tires have the best footprint even if properly inflated.
Originally Posted by JLTD
Originally Posted by SpitFire6
Originally Posted by JLTD
Sorry but I have to say
With these kind of threads there are usually so many different opinions that it is completely baffling to everyone.
I have always found with my vehicles that a few psi above what is placarded gives me the most even tire wear and longest tire life. How much over was a function of the weight of the vehicle, and the quality of the tire - cheaper tires were more sensitive to excessive wear.
A couple of real life examples - in a 2004 Jeep grand Cherokee, I bought the vehicle with 18,000 miles with tires at exactly placarded pressure. The front tires were worn almost smooth on the inside and outside edges, while the center of the tread was hardly worn at all. The rears were in similar condition so tires had been rotated. It would wash out badly in the rain, so the tires were soon replaced and over the next 80,000 I experienced even wear by running them at a higher pressure and rotating every 10,000 miles.
In a 2013 Ford F1 50, the same was also true - much more wear on the inner and outer edges of the front tires. It benefited from higher psi, and also when towing or hauling a load the owners manual recommended Increasing psi for more load carrying ability.
Hi,
Sorry, I thought increasing the pressure would increase centre wear.
Cheers,
Iain.
It will, but only if you go too high on the pressure.
...... and too high here could mean delta exceeding 20-30 psi , IDK .
Originally Posted by SpitFire6
Originally Posted by JLTD
Sorry but I have to say
With these kind of threads there are usually so many different opinions that it is completely baffling to everyone.
I have always found with my vehicles that a few psi above what is placarded gives me the most even tire wear and longest tire life. How much over was a function of the weight of the vehicle, and the quality of the tire - cheaper tires were more sensitive to excessive wear.
A couple of real life examples - in a 2004 Jeep grand Cherokee, I bought the vehicle with 18,000 miles with tires at exactly placarded pressure. The front tires were worn almost smooth on the inside and outside edges, while the center of the tread was hardly worn at all. The rears were in similar condition so tires had been rotated. It would wash out badly in the rain, so the tires were soon replaced and over the next 80,000 I experienced even wear by running them at a higher pressure and rotating every 10,000 miles.
In a 2013 Ford F1 50, the same was also true - much more wear on the inner and outer edges of the front tires. It benefited from higher psi, and also when towing or hauling a load the owners manual recommended Increasing psi for more load carrying ability.
Hi,
Sorry, I thought increasing the pressure would increase centre wear.
Cheers,
Iain.
It will, but only if you go too high on the pressure.
...... and too high here could mean delta exceeding 20-30 psi , IDK .
Last edited:
Originally Posted by Mark72
I have a 4 door car that requires 30 PSI cold tire pressure. I noticed the front tires were sagging a little so I checked them and the gauge read 38. I also tested it against 2 other gauges a d its accurate. If I lower the cold air pressure to 30 or even 32 those tires are going to be sagging even more. My question is should I just go by what's required and not worry how the tire looks?
It's easy:
1. Check the driver's door tire placard and confirm the tires mounted on your car are EXACTLY the same size and type as indicated on the door placard. You have not confirmed this.
2. If the same, when the tires are cold, preferably first thing in the morning after standing overnight, set the tire pressures to that indicated on the door placard.
3. Check regularly and adjust as required.
HTH
I have a 4 door car that requires 30 PSI cold tire pressure. I noticed the front tires were sagging a little so I checked them and the gauge read 38. I also tested it against 2 other gauges a d its accurate. If I lower the cold air pressure to 30 or even 32 those tires are going to be sagging even more. My question is should I just go by what's required and not worry how the tire looks?
It's easy:
1. Check the driver's door tire placard and confirm the tires mounted on your car are EXACTLY the same size and type as indicated on the door placard. You have not confirmed this.
2. If the same, when the tires are cold, preferably first thing in the morning after standing overnight, set the tire pressures to that indicated on the door placard.
3. Check regularly and adjust as required.
HTH
- Status
