P-metric and LT construction

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buck91

buck91

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what is the difference between a p-metric tire and an LT tire with Load C rating? I understand that modern radial tires don't actually have 10 plies or 8 plies or whatever in the LT side, but I'm looking at a couple tires that have almost identical ratings between p-metric and LT load range C in a particular size and I'm trying to determine if the LT Load C will offer any advantage.
 
P tires have to knock 10% off their load rating when on a truck.

Your door jamb will mention P, P XL, or LT. My F150 took XLs and had to be aired up to 41 PSI.

Generally LT starts on 3/4 ton trucks.
 
I understand that, just asking if there is a construction difference between the P's and the load C if the lbs rating is the same?
 
LTs typically cost $30-50 more per tire vs their P-metric counterparts. My truck came with LTs. I'm thankful it came with very good tires from the factory (Silent Armor ProGrade), but I don't look forward to the day they need replacing.
 
Lt tires come on 1/2ton trucks as well. I had an 03 chevy with lt's on it. If you have a 1/2 ton on bigger you want lt's.

They are built stronger (stiffer side walls, stronger tire carcess and more agressive tread patterns).

P-metric only come in "b" load range. anything higher is an lt.
The lbs rating is deffintly not the same. lt's are rated higher because they are built stronger.

On a truck you deffintly want a stronger tire (lt tire) to handle the higher forces vs a car.
 
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An LT tire has to have higher pressures to carry the same weight! If you runan LT tire at P pressures, they will run very hot and can fail. Thus, while an LT can carry more weight, it does so by using higher pressures and will give a harsher ride. This is usually not an issue on trucksused for commerce but may be an isssue to you for comfort reasons.
 
I don't understand why so many half ton trucks come with P-rated tires. A truck should have LT tires.

I have load range E tires on my Cherokee. I have to run them at 30PSI otherwise it will, literally, bounce the Jeep off of the road.

The thicker sidewalls are nice - they apparently can act as a run flat tire!
 
Quote:
I don't understand why so many half ton trucks come with P-rated tires. A truck should have LT tires.
Why? Many (most?) pickups are used as personal or family cars, anyway. The non-LT tires deliver long life and great service, and a better ride than LT, for many tens of thousands of miles for millions of 150/1500-class pick up truck drivers.

Don't claim that a P tire isn't a light truck tire--any Goodyear Wrangler or Michelin LTX or many other lines with both P and LT are light truck tires suitable for the trucks they're spec'ed on.

Load Range B...does it exist any longer? We have Standard Load, and Extra Load, then Load Range C and up. Your Standard Load pick up truck tires will have 2 ply sidewalls. Load Range C and D tires will have.....2 ply sidewalls.
 
I have been told to NEVER run a P-tire on a typical full size truck. Are you all sure its OK for general everyday non-hauling use??? (Not disagreeing, just asking)
 
Originally Posted By: buck91
I understand that, just asking if there is a construction difference between the P's and the load C if the lbs rating is the same?


Yes, and just an FYI. The Michelin website has an error and they quote the LT load rating for a P metric tire. needless to say this complicates the discussion.

So to further explain:

A P235/75R15 STANDARED LOAD (SL) has a load carrying capacity of 2028# at 35 psi, and a maximum pressure of 35, 44, or 51 psi.

A P235/75R15 EXTRA LOAD (XL) has a load carrying capacity of 2183# at 41 psi, with a maximum pressure of 41 or 50 psi.

Compare to a SL, an XL has slightly stronger sidewall plies and a slightly stronger steel belt. Both might have cap plies, with the XL being more likely.

An LT235/75R15 Load Range C has a load carrying capacity of 1985# at 50 psi.

Compared to an XL, a LT LRC has slightly stronger plies, and a slightly stronger steel belt, and MIGHT have cap plies.

But here's where the real difference is: An LT will be built with a stiffer, but stronger rubber material to withstand the load intensity of the higher load ranges.

Load Intensity? The amount of load compared to how big the tires is - generally related to the inflation pressure.

Explanation? If P type rubber compounds were to be used on an LT tire, they would fail in manner called "Compression Set" - a version of "creep". Since rubber is a viscoelastic material and it behaves somewhat like a very viscous liquid and somewhat like a elastic material, ALL rubber compounds exhibit this kind of behavior, so it's a matter of degree.

And lastly: P metric tires on a 1/2 ton PU? There's this transition between P type tires and LT type tires that occurs right where 1/.2 ton picks live. P type tires ride better, due to the lower pressure, which is one of the reasons they are chosen by the OEM's. Since most 1/2 ton buyers use the vehicle like a car, it's a good choice.
 
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Originally Posted By: Miller88
I don't understand why so many half ton trucks come with P-rated tires. A truck should have LT tires.

I have load range E tires on my Cherokee. I have to run them at 30PSI otherwise it will, literally, bounce the Jeep off of the road.

The thicker sidewalls are nice - they apparently can act as a run flat tire!


If your truck can meet its max payload and towing capacities on a P-rated tire, then what benefit is there to using an LT tire?
 
Originally Posted By: CapriRacer


So to further explain:

A P235/75R15 STANDARED LOAD (SL) has a load carrying capacity of 2028# at 35 psi, and a maximum pressure of 35, 44, or 51 psi.

A P235/75R15 EXTRA LOAD (XL) has a load carrying capacity of 2183# at 41 psi, with a maximum pressure of 41 or 50 psi.

----

An LT235/75R15 Load Range C has a load carrying capacity of 1985# at 50 psi.

----

And lastly: P metric tires on a 1/2 ton PU? There's this transition between P type tires and LT type tires that occurs right where 1/.2 ton picks live. P type tires ride better, due to the lower pressure, which is one of the reasons they are chosen by the OEM's. Since most 1/2 ton buyers use the vehicle like a car, it's a good choice.


Interesting that the LT 235/75R15 load C has less capacity than the P235/75R15 STANDARED LOAD (SL).

Which brings the question,

---When should a 1/2ton driver move to LT tires?---

I'm interested in the answer--- here's my case: Tundra V8 double cab. commutes 5 days a week. already runs stiff in the rear. So that favors a P. However, I tow a 6000lb load once per month, often out of town, so the truck gets worked regularly, which would suggest an LT. Yet, the current tires are rated at 2400lbs max per tire (Destination LE2s on it now, P265/70R16) and seem to handle it ok.

The rears wear faster than the front, which I've never experienced in a vehicle before, about twice the rate. I have assumed it's because of the towing.

Thoughts?
 
My suburban shares nearly every single part with its equivalent 1500 truck sibling. I bought it to work hard, tow and do the job. A 2500 version of the same vehicle uses a LT load range E tire. So I put the same load range E tires on my 1500 anyway and couldn't be happier. They wear, handle and perform the work much better. If/when the suburban dies, any truck that I will own will be used for work. So I will find the matching load range E tire to put on it. I have had both and I won't settle for anything else.

P rated tires on a truck is just not a good idea, no matter how much weight they specify. P rated handle like sponges and wear prematurely from my experience. If its a truck, put truck tires on it and you are covered for anything that the truck may be asked to perform. The last thing you want to do is short change yourself or be sitting on the side of the road changing out overwhelmed tires.
 
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Quote:
But here's where the real difference is: An LT will be built with a stiffer, but stronger rubber material to withstand the load intensity of the higher load ranges.

Load Intensity? The amount of load compared to how big the tires is - generally related to the inflation pressure.

Explanation? If P type rubber compounds were to be used on an LT tire, they would fail in manner called "Compression Set" - a version of "creep". Since rubber is a viscoelastic material and it behaves somewhat like a very viscous liquid and somewhat like a elastic material, ALL rubber compounds exhibit this kind of behavior, so it's a matter of degree.

So does this mean that a 1/2-ton truck that is loaded heavy much of the time will have better tire results with LT tires? (Assuming equal or higher load capacity and correct O.D. and width, and correct inflation pressure for the load on this type of tire.)
 
My two cents:

I run E rated tires on my half tons because they are trucks, I load the heck out of them and the thicker tires do better with nails and screws.

The downside is they ruin the trucks ride.
 
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Originally Posted By: meep
Interesting that the LT 235/75R15 load C has less capacity than the P235/75R15 STANDARD LOAD (SL)........


Darn!! I knew I forgot something. I should have also posted the derated loads for P type tires when used on LT vehicles so the comparisons would be equal. Here they are:

P235/75R15 SL 1844# at 35 psi

P235/75R15 XL 1985 @ 41 psi.

LT235/75R15 LRC 1985# @ 50 psi.

Please note the LT and the XL are the same, but the pressure is 15 psi higher for the LT.


Originally Posted By: meep
.......Which brings the question,

---When should a 1/2ton driver move to LT tires?---

I'm interested in the answer--- here's my case: Tundra V8 double cab. commutes 5 days a week. already runs stiff in the rear. So that favors a P. However, I tow a 6000lb load once per month, often out of town, so the truck gets worked regularly, which would suggest an LT. Yet, the current tires are rated at 2400lbs max per tire (Destination LE2s on it now, P265/70R16) and seem to handle it ok.

The rears wear faster than the front, which I've never experienced in a vehicle before, about twice the rate. I have assumed it's because of the towing.

Thoughts?


Personally, I am not a fan of moving from P type to LT type tires. At the very least it requires 15 psi more to get the same load carrying capacity - and the truck isn't set up for that kind of pressure (meaning spring rated and shock damping rates and it is questionable that the wheels are rated for that kind of pressure.)
 
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