tire pressure advice
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Fleet Mechanic
Joined: May 2005
Posts: 1,739
Likes: 14
From: Vale, NC
tire pressure advice
I can't get the search feature to work, so there may be info here I couldn't get.
I went out to my Screw this morning to start a 400 mile trip. I figured I'd check the tire pressure just to make sure I wasn't leaving any extra $ at the pumps. I had just filled them last week but I thought it was worth a check. Sure enough they were at about 30psi. The temp was colder - probably 60 degrees F this morning - but that seemed a bit low. I searched the tire blackwall all over and could not find a recommended pressure. There was info about the load, but not a recommended psi. I mean it.... I searched 3 times and I do know how to read
So, I filled them up to 34psi cold thinking a little added pressure might be ok for the long highway trip today. Sure enough, I got 18.82 mpg - little bit of a side/tail wind. Unfortunately, I picked up a nail and when I checked the pressure that afternoon it was 38psi.
My question - is it safe to run tires with a bit more pressure when you are highway driving without a load to increase mileage? Are there some key "rules of thumb" about tire pressure I should know?
I went out to my Screw this morning to start a 400 mile trip. I figured I'd check the tire pressure just to make sure I wasn't leaving any extra $ at the pumps. I had just filled them last week but I thought it was worth a check. Sure enough they were at about 30psi. The temp was colder - probably 60 degrees F this morning - but that seemed a bit low. I searched the tire blackwall all over and could not find a recommended pressure. There was info about the load, but not a recommended psi. I mean it.... I searched 3 times and I do know how to read
So, I filled them up to 34psi cold thinking a little added pressure might be ok for the long highway trip today. Sure enough, I got 18.82 mpg - little bit of a side/tail wind. Unfortunately, I picked up a nail and when I checked the pressure that afternoon it was 38psi.
My question - is it safe to run tires with a bit more pressure when you are highway driving without a load to increase mileage? Are there some key "rules of thumb" about tire pressure I should know?
Posting Guru
Joined: Dec 2006
Posts: 1,466
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From: N. Fort Myers,FL
Usually there isnt a "recommended" tire pressure on tires.
I air my rear tires up to 60psi(load range D) and my fronts to like 45psi.
At work we air tires up according to the Load Range(mainly because it would be a nusance to have to air the tires up everytime they tow a trailer). The Load range E's we air up to 70-75psi, the D's up to 50-55psi, the C's to 45-50, and the P rated to about 40psi.
But there is a forumla to find out how much air you should have in your tires though.
I air my rear tires up to 60psi(load range D) and my fronts to like 45psi.
At work we air tires up according to the Load Range(mainly because it would be a nusance to have to air the tires up everytime they tow a trailer). The Load range E's we air up to 70-75psi, the D's up to 50-55psi, the C's to 45-50, and the P rated to about 40psi.
But there is a forumla to find out how much air you should have in your tires though.
Postmaster
Joined: May 2003
Posts: 3,310
Likes: 9
From: E.Lincoln County, NC
Just be glad you don't have that irritating tire pressure monitoring system like my '08 E350 does. Every time it cools off a bit that darn light comes on. I'm about to put a piece of black tape over it!
If you're running the original tire size the recommended inflation pressure is on the door sticker. Whatever you run the tire should say "Max load xxxlbs @ xx psi".
"Proper tire inflation pressure is the specified air pressure given by a car maker for a certain tire on a specific vehicle. This pressure specification should not be confused with a tire's maximum pressure, which is usually listed on the tire's sidewall."
If you're running the original tire size the recommended inflation pressure is on the door sticker. Whatever you run the tire should say "Max load xxxlbs @ xx psi".
"Proper tire inflation pressure is the specified air pressure given by a car maker for a certain tire on a specific vehicle. This pressure specification should not be confused with a tire's maximum pressure, which is usually listed on the tire's sidewall."
Senior User
Joined: Dec 2006
Posts: 382
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From: Green Bay WI. / Wawa Ont.
"Proper tire inflation pressure is the specified air pressure given by a car maker for a certain tire on a specific vehicle. This pressure specification should not be confused with a tire's maximum pressure, which is usually listed on the tire's sidewall."[/quote]
Correct, always go by the door plate. Of course a couple extra lbs. is ok, lower rolling resistance.
Correct, always go by the door plate. Of course a couple extra lbs. is ok, lower rolling resistance.
Elder User
Joined: Nov 2005
Posts: 788
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From: Cottage Grove, Minnesota
Okay guys i have question here. I just put on some new tires friday. I went from P255/70R16 to a LT245/75R16E. My old tires i ran at 35psi and all was great. With the new tires they told me run them at 40psi. They have a max of 80psi. I'm really wondering what is a good pressure? I have them right now at about 60psi and they are a lot better in handling than 40.
Senior User
Joined: Apr 2004
Posts: 352
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From: Millbrook, AL
18.82 mpg huh...so far the best I've got is 16.86. Same truck. I notice you've got electric fans and a diablo. Which one was the best investment? Are eletric fans loud? Do they run all the time? Are you running high test for the diablo? I know I bought a pickup truck but two mpg sure would help. Thanks
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Senior User
Joined: Dec 2006
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From: Green Bay WI. / Wawa Ont.
Okay guys i have question here. I just put on some new tires friday. I went from P255/70R16 to a LT245/75R16E. My old tires i ran at 35psi and all was great. With the new tires they told me run them at 40psi. They have a max of 80psi. I'm really wondering what is a good pressure? I have them right now at about 60psi and they are a lot better in handling than 40.
You could be way over with 60.
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Posting Guru
Joined: Apr 2005
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From: Edgerton, WI
It tells you on the door jamb what the suggested tire pressure it. Thats not a hard figure though, because if you haul a load you would run more tire pressure and if you are driving off-road you may let some air out of the tires to get more traction.
My truck says 35 psi, but I run 40 in the front to offset the weight of the engine. When Im hauling a load of firewood, I will air the tires up to 60 psi.
What it says on the door jamb is more of a suggestion. Its not as if you tires are going to explode if you run more pressure than that. As long as you dont exceede the max psi that it says on the sidewall of the tire, you will be fine.
My brother has a '99 F-250 and he runs his tires at 60 psi all the time.
My truck says 35 psi, but I run 40 in the front to offset the weight of the engine. When Im hauling a load of firewood, I will air the tires up to 60 psi.
What it says on the door jamb is more of a suggestion. Its not as if you tires are going to explode if you run more pressure than that. As long as you dont exceede the max psi that it says on the sidewall of the tire, you will be fine.
My brother has a '99 F-250 and he runs his tires at 60 psi all the time.
Thread Starter
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Fleet Mechanic
Joined: May 2005
Posts: 1,739
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From: Vale, NC
18.82 mpg huh...so far the best I've got is 16.86. Same truck. I notice you've got electric fans and a diablo. Which one was the best investment? Are eletric fans loud? Do they run all the time? Are you running high test for the diablo? I know I bought a pickup truck but two mpg sure would help. Thanks
The 18.82 was in Florida - flat as a pancake - running with the wind on 93 octane. I did really like the change from the Diablo and I got it for $65 off ebay. Got lucky on that one.
I've gone up to about 38 psi hot on te tires. The temps around here keep fluctuating from low 50s at night to low 80s during the day. Haven't got two days the same in a while. If a few more psi will help with mileage it seems worth it providing it isn't just dissolving the tires.
Posting Guru
Joined: Feb 2007
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My F150 4X4 recommends 35 PSI on the door jam. The original Firestone tires say "Never Exceed 40 PSI" on the sidewall.
My truck says 35 psi, but I run 40 in the front to offset the weight of the engine. When Im hauling a load of firewood, I will air the tires up to 60 psi.
What it says on the door jamb is more of a suggestion. Its not as if you tires are going to explode if you run more pressure than that. As long as you dont exceede the max psi that it says on the sidewall of the tire, you will be fine.
What it says on the door jamb is more of a suggestion. Its not as if you tires are going to explode if you run more pressure than that. As long as you dont exceede the max psi that it says on the sidewall of the tire, you will be fine.
Elder User
Joined: Sep 2007
Posts: 700
Likes: 1
From: waterloo, iowa
Okay guys i have question here. I just put on some new tires friday. I went from P255/70R16 to a LT245/75R16E. My old tires i ran at 35psi and all was great. With the new tires they told me run them at 40psi. They have a max of 80psi. I'm really wondering what is a good pressure? I have them right now at about 60psi and they are a lot better in handling than 40.
It's pretty much trial and error with a piece of chalk to show you if your tire is riding flat.
Posting Guru
Joined: Apr 2005
Posts: 1,290
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From: Edgerton, WI
I just went out and checked my Goodyears and they say max psi is 50. It varies from tire to tire, so you cant go by what it says on the door jamb.
Senior User
Joined: Dec 2006
Posts: 382
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From: Green Bay WI. / Wawa Ont.
The maximum pressure on the sidewall is what the tire can handle safely. It has nothing to do with what the vehicle can handle. The door post gives you the pressure that is optimum for the vehicle.
Thread Starter
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Fleet Mechanic
Joined: May 2005
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From: Vale, NC
So I'm still a little confused, but I think this is the summary:
1. Start by checking door jam to see what the factory recommendations are - these will vary depending on the vehicle, it's GVW, etc. - as that provides a good starting point.
2. Check the sidewall of the tire to determine the maximum load - going over that is bad and possibly dangerous.
3. Grab a piece of chalk and mark your tires as described in the inflation post (#4) to get the best practical read on inflation levels.
4. Consistently check inflation as temperature, time, and other factors constantly change your inflation.
Sound right?
1. Start by checking door jam to see what the factory recommendations are - these will vary depending on the vehicle, it's GVW, etc. - as that provides a good starting point.
2. Check the sidewall of the tire to determine the maximum load - going over that is bad and possibly dangerous.
3. Grab a piece of chalk and mark your tires as described in the inflation post (#4) to get the best practical read on inflation levels.
4. Consistently check inflation as temperature, time, and other factors constantly change your inflation.
Sound right?