what psi to use
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Nick1994
$100 site donor 2024
25 psi is way too low. I wouldn't go under 35.
Nick1994
$100 site donor 2024
Originally Posted By: Ramblejam
Originally Posted By: Nick1994
25 psi is way too low. I wouldn't go under 35.
That's wonderful. Will you please back up your opinion with something other than anecdotal beliefs?
You do realize this is on a truck right? And not a Pinto?
I had a similar truck with the same size tires, if they were at 25 psi there's no way they would have held together. It wore unevenly on the edges at 35 psi. The pavement in The desert gets to 175+ degrees, if you'd have a truck with tires at 25 psi on the interstate in the heat then all I have to say is good luck to you and to everyone driving around you.
Originally Posted By: Nick1994
25 psi is way too low. I wouldn't go under 35.
That's wonderful. Will you please back up your opinion with something other than anecdotal beliefs?
You do realize this is on a truck right? And not a Pinto?
I had a similar truck with the same size tires, if they were at 25 psi there's no way they would have held together. It wore unevenly on the edges at 35 psi. The pavement in The desert gets to 175+ degrees, if you'd have a truck with tires at 25 psi on the interstate in the heat then all I have to say is good luck to you and to everyone driving around you.
Originally Posted By: Nick1994
You do realize this is on a truck right?
This is a F-150, with a curb weight of around 5,000lbs.
40% of that, or around 2,000lbs. is on the rear axle.
In other words, 1,000lbs. per tire.
According to the TRA flotation table, per tire (31x10.5R15LT):
25PSI - 1400lbs.
30PSI - 1595lbs.
35PSI - 1765lbs.
40PSI - 1945lbs.
45PSI - 2100lbs.
50PSI - 2270lbs.
So, unloaded @ 25PSI per rear tire, Dallas has 800lbs. of extra load capacity. Should he exceed this number, then he can adjust pressure accordingly.
Then again, this is just the Tire and Rim Association (standardizing body for the tire, rim, valve and allied parts industry for the United States) -- what do they have on Nick from Arizona, right?
You do realize this is on a truck right?
This is a F-150, with a curb weight of around 5,000lbs.
40% of that, or around 2,000lbs. is on the rear axle.
In other words, 1,000lbs. per tire.
According to the TRA flotation table, per tire (31x10.5R15LT):
25PSI - 1400lbs.
30PSI - 1595lbs.
35PSI - 1765lbs.
40PSI - 1945lbs.
45PSI - 2100lbs.
50PSI - 2270lbs.
So, unloaded @ 25PSI per rear tire, Dallas has 800lbs. of extra load capacity. Should he exceed this number, then he can adjust pressure accordingly.
Then again, this is just the Tire and Rim Association (standardizing body for the tire, rim, valve and allied parts industry for the United States) -- what do they have on Nick from Arizona, right?
25 sounds good to me. I run 28 in a similar size tire on a crew cab and it wears perfect. I used to run 17 in the rear of a Nissan 4x4 and ran it hard. The TRA has it right, its all about the load.
I run 26 in my jeep with 31's and they seem to wear even
Wow, don't you guys get [censored] gas mileage running such low pressure? I run 35 in all four on my F150, as I did on my Tundra for 10 years before that.
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Originally Posted By: Nick1994
Originally Posted By: Ramblejam
Originally Posted By: Nick1994
25 psi is way too low. I wouldn't go under 35.
That's wonderful. Will you please back up your opinion with something other than anecdotal beliefs?
You do realize this is on a truck right? And not a Pinto?
I had a similar truck with the same size tires, if they were at 25 psi there's no way they would have held together. It wore unevenly on the edges at 35 psi. The pavement in The desert gets to 175+ degrees, if you'd have a truck with tires at 25 psi on the interstate in the heat then all I have to say is good luck to you and to everyone driving around you.
The tire is steel belted? Over the tread, and textile body? Too much pressure can wear the edges, by expanding the body and not the stronger center
Yes, I have seen this.
Rod
Originally Posted By: Ramblejam
Originally Posted By: Nick1994
25 psi is way too low. I wouldn't go under 35.
That's wonderful. Will you please back up your opinion with something other than anecdotal beliefs?
You do realize this is on a truck right? And not a Pinto?
I had a similar truck with the same size tires, if they were at 25 psi there's no way they would have held together. It wore unevenly on the edges at 35 psi. The pavement in The desert gets to 175+ degrees, if you'd have a truck with tires at 25 psi on the interstate in the heat then all I have to say is good luck to you and to everyone driving around you.
The tire is steel belted? Over the tread, and textile body? Too much pressure can wear the edges, by expanding the body and not the stronger center
Yes, I have seen this.
Rod
It is PSIG and not PSI. Ed
I run 33 psi in my 31's they wear great.
Depends on the weight. Previous 3 vehicles I have owned, when tires inflated to door jamb numbers, would wear nastily on the outside edges; the F150 I just got with 275/65R18 tires is no exception to that situation-- the tires were at around 30psi and were wearing quite a bit more on the edges at only 22k miles. Max inflation on the tires is 45 and they are now at 40 to test wear.
IMO tires should be inflated so you get even wear, both for longevity and the largest contact patch. (Unless you borrow your buddy's car in college and pump up the 35psi tires to 50(!) to save on gas.
)
Load the truck and another change would be indicated.
IMO tires should be inflated so you get even wear, both for longevity and the largest contact patch. (Unless you borrow your buddy's car in college and pump up the 35psi tires to 50(!) to save on gas.
Load the truck and another change would be indicated.
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Originally Posted By: Ramblejam
Originally Posted By: Nick1994
You do realize this is on a truck right?
This is a F-150, with a curb weight of around 5,000lbs.
40% of that, or around 2,000lbs. is on the rear axle.
In other words, 1,000lbs. per tire.
According to the TRA flotation table, per tire (31x10.5R15LT):
25PSI - 1400lbs.
30PSI - 1595lbs.
35PSI - 1765lbs.
40PSI - 1945lbs.
45PSI - 2100lbs.
50PSI - 2270lbs.
So, unloaded @ 25PSI per rear tire, Dallas has 800lbs. of extra load capacity. Should he exceed this number, then he can adjust pressure accordingly.
Then again, this is just the Tire and Rim Association (standardizing body for the tire, rim, valve and allied parts industry for the United States) -- what do they have on Nick from Arizona, right?
Be certain to NEVER run those tires underinflated according to that table. If you ever increase the weight that they are carrying you must increase the pressure. This is especially true when you run them in hot weather on hot roads. If you ever apply more load and do not increase the pressure those tires will blow. Before they blow you may get a warning if you know what to look for. When the rubber over heats because of the combination of hot road way, hot air, over load causing too much flexing of the rubber, and underinflation allowing too much flexing, it will feel like the tires are sliding on ice. If you ever feel tires doing that you have to pull over and let them cool off, or they will blow out.
If you have to, run tires with more pressure than the load requires, such as when you are going to run them loaded up during one part of a trip, but not loaded up during another part of a trip. It is OK to run them over inflated sometimes, though you may not get the best ride from them when they are over inflated.
Originally Posted By: Nick1994
You do realize this is on a truck right?
This is a F-150, with a curb weight of around 5,000lbs.
40% of that, or around 2,000lbs. is on the rear axle.
In other words, 1,000lbs. per tire.
According to the TRA flotation table, per tire (31x10.5R15LT):
25PSI - 1400lbs.
30PSI - 1595lbs.
35PSI - 1765lbs.
40PSI - 1945lbs.
45PSI - 2100lbs.
50PSI - 2270lbs.
So, unloaded @ 25PSI per rear tire, Dallas has 800lbs. of extra load capacity. Should he exceed this number, then he can adjust pressure accordingly.
Then again, this is just the Tire and Rim Association (standardizing body for the tire, rim, valve and allied parts industry for the United States) -- what do they have on Nick from Arizona, right?
Be certain to NEVER run those tires underinflated according to that table. If you ever increase the weight that they are carrying you must increase the pressure. This is especially true when you run them in hot weather on hot roads. If you ever apply more load and do not increase the pressure those tires will blow. Before they blow you may get a warning if you know what to look for. When the rubber over heats because of the combination of hot road way, hot air, over load causing too much flexing of the rubber, and underinflation allowing too much flexing, it will feel like the tires are sliding on ice. If you ever feel tires doing that you have to pull over and let them cool off, or they will blow out.
If you have to, run tires with more pressure than the load requires, such as when you are going to run them loaded up during one part of a trip, but not loaded up during another part of a trip. It is OK to run them over inflated sometimes, though you may not get the best ride from them when they are over inflated.
gathermewool
Site Donor 2023
Originally Posted By: Eddie
It is PSIG and not PSI. Ed
For whatever reason this used to bug me, too. In context; however, 'PSI' is fine. I wasn't confused.
I come across a tech manual or procedure every so often that will list units of 'psi.' We don't use pressure instruments or gages that read out in PSIA, so PSIG is assumed.
It is PSIG and not PSI. Ed
For whatever reason this used to bug me, too. In context; however, 'PSI' is fine. I wasn't confused.
I come across a tech manual or procedure every so often that will list units of 'psi.' We don't use pressure instruments or gages that read out in PSIA, so PSIG is assumed.
Originally Posted By: Tones
Wow, don't you guys get [censored] gas mileage running such low pressure? I run 35 in all four on my F150, as I did on my Tundra for 10 years before that.
assuming an empty truck no. Fronts would be a higher pressure since the front is so heavy. An empty bed would be fine @ 25.
Wow, don't you guys get [censored] gas mileage running such low pressure? I run 35 in all four on my F150, as I did on my Tundra for 10 years before that.
assuming an empty truck no. Fronts would be a higher pressure since the front is so heavy. An empty bed would be fine @ 25.
I was thinking it was higher on my 1991 Bronco with stock 31x10.5 on it and this is what I found - see post#10:
http://www.fullsizebronco.com/forum/showthread.php?t=50999
40 PSIG
http://www.fullsizebronco.com/forum/showthread.php?t=50999
40 PSIG
Man, you guys are all over the ball park.
Step 1) Find the vehicle tire placard. On Ford trucks, it's located on the driver's door. It will list the original tire size and the specified pressure for that size.
Note: Pickup trucks come in so many configurations that it is impossible to know what the vehicle tire placard says unless you actually look at it. Best guess for a 1987 F-150: P235/75R15 XL at 35 psi front/41 psi rear.
Step 2) Match the original load carrying capacity.
Note: On pickup trucks, vans, and trailer, P type tires have to derated in load carrying capacity by a factor of 1.1
So a P235/75R15 at 35/41 has a truck rated capacity of 1844#/1985# and inorder to carry that load a 31x10.50R15LT needss to use 37/42 psi.
OP: What does the vehicle tire placard say?
Step 1) Find the vehicle tire placard. On Ford trucks, it's located on the driver's door. It will list the original tire size and the specified pressure for that size.
Note: Pickup trucks come in so many configurations that it is impossible to know what the vehicle tire placard says unless you actually look at it. Best guess for a 1987 F-150: P235/75R15 XL at 35 psi front/41 psi rear.
Step 2) Match the original load carrying capacity.
Note: On pickup trucks, vans, and trailer, P type tires have to derated in load carrying capacity by a factor of 1.1
So a P235/75R15 at 35/41 has a truck rated capacity of 1844#/1985# and inorder to carry that load a 31x10.50R15LT needss to use 37/42 psi.
OP: What does the vehicle tire placard say?
Originally Posted By: Nick1994
25 psi is way too low. I wouldn't go under 35.
Im with Nick, my 2006 Silverado extended cab 4X4 gets 35 psi exactly in all four corners, with a trailer or a heavy load in the bed I bump the rears up to 38 psi.
25 psi is way too low. I wouldn't go under 35.
Im with Nick, my 2006 Silverado extended cab 4X4 gets 35 psi exactly in all four corners, with a trailer or a heavy load in the bed I bump the rears up to 38 psi.
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