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Topic: LT tires vs. P rated

Posted By: Jayco-noslide on 05/14/10 01:22pm

Just bought a 2007 Chevy half-ton Silverado to replace a 2000 half-ton to tow our 25 ft. 5th wheel. I've always put on LT tires because I understand there is less flex in the sidewalls and they are preferred for much of a load. But the 2007 comes with P rated tires which I think are more of a car tire. I plan to go ahead and use them as they are too good yet to replace but just wondering if anyone thinks I will notice any problems. Our 5er is light as 5ers go at just 5,200 lbs dry wt. so probably around 6500 loaded. I've had no tire problems and no problems towing it with half-tons.


Jayco-noslide


Posted By: JJBrown on 05/14/10 01:26pm

Have a look at my thread on the same question i asked....

do a search on "LT Tire Question"


Posted By: LIKE2BUILD on 05/14/10 01:39pm

I believe P-metric tires are rated for C load range and a max pressure of 35PSI. Some may also be rated up to 41PSI. To me, those low pressure ratings would equate to a pretty squishy side wall. I would think with a 5er, even as small as yours, you'd feel some wiggle and jiggle in the rear end from this.

KJ


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Posted By: kmbelt on 05/14/10 01:56pm

I had p-metric tires on my last truck. Even towing the 4000# popup they were horrible. Squirmy as heck and made for a horrible ride. THey didn't last long and I upgraded to LT tires. Made all the difference in the world. Tow a couple of times and you'll see what i mean. The stronger sidewalls make all the difference in the world.


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Posted By: Terryallan on 05/14/10 03:13pm

On the side wall. It will give the actual weight the tires are designed to carry. Something like 2250lb per tire I'm guessin. If you plan on the truck (not the truck and trailer) weighing more than 9000lbs, which will be way over your 1500s GVWR. Or plan on having more than 4500lbs on the rear tires. You would need to get new tires.

However if they are rated to carry your weight, and, as you say, You plan to try them anyway. Use them and determin for yourself how they do. I believe. If you are within the rated weights. They will do fine. You are the only one they have to please


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Posted By: fivecodys on 05/14/10 03:53pm

I have them "P" on my truck and they are SQUISHY!
Going to LT's next month.
Everyone seems to be of the same mind that moving to an LT makes a huge differece when towing.
I imagine that the unloaded truck will ride a bit stiffer but...it's a truck.
It's ok if it rides like one.

Bill


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Posted By: music69 on 05/16/10 05:10pm

My next tires will be LT, but the stock Goodyear Wrangler A/T tires have a max pressure of 44 psi. Running them at max pressure while towing is *much* better than the 35 psi "daily driving" pressure, and they do not get hot.


Posted By: mowermech on 05/16/10 06:16pm

JIMNLIN wrote:

P tires.

The newer P are metric and 44 psi rated. P tires capacity on a truck are required by DOT to be derated roughly 10 percent.


Can you give us the reference for the DOT regulation that states this, Please?


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Posted By: jdog on 05/16/10 02:00am

P tires are car tires for softer ride not for carrying weight as LT (light truck)tires are. I used to have "P" tires on a 1/2 ton towing 6000 lbs. The tires started blowing out. Lost two tires in two days. Went to "LT" tires and never bought another "P" tire on any truck I had. P tires are not safe for towing! They will blow out sooner or later. They get hotter faster and blow when carring weight.


Posted By: traveling1253 on 05/15/10 05:18am

While the OEM tires are rated to carry anything a 1/2 ton truck should be carrying, a real LT truck tire will "feel" better when loaded down. Running LRE Michelins on my Sierra. Overkill? Yes but always hated the mushy/wallowing riding on marshmallows feeling I got with the wimpy P rated tires when carrying a load of firewood. My butt is much happier now when the truck is loaded down or towing with the LT tires. Unloaded the ride is a bit stiffer but still comfortable running 40-45 PSI, 55-60 with a load. Noticed a 1 MPG drop due to the heavier tire as well.


Posted By: mayo30 on 05/14/10 07:18pm

I just changed my P tires to LT load range E.I have no idea why the dealer had P tires on it other then something to do with price.The P side walls are very flexible and I was seeing premature wear.PLUS I did not like the handling or feel safe pulling a heavy load.I lived withn the P for 22000 klms.This is the first truck I have had with P tires,never again.


Posted By: old guy on 05/14/10 07:32pm

I think like the rest, you will be buying LT tires before long. You may not get much in a trade in so sell them out right.


Posted By: JIMNLIN on 05/14/10 07:39pm

My wifes '06 1500 chevy crew cab 4x4 came with P rated tires. At 40k I just swapped them out for LT same size load range C at 50 psi. Much better ride and better stability pulling a 8700 gross bumper pull trailer with a tractor/FEL/7' mower. I think the empty truck ride is better with the C's as the P tires sidewall are soft with more compression and more rebound going over bumps (basketball bounce).

The C tires were only two lbs heavier per tire than the P tires.

The newer P are metric and 44 psi rated. P tires capacity on a truck are required by DOT to be derated roughly 10 percent.


"good judgment comes from experience, and a lot of that comes from bad judgment" ............ Will Rogers

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Posted By: chrispitude on 05/14/10 08:32pm

I had LT-Ds (BFG All-Terrain K/O) on my 2005 Toyota Tundra V8 4x4, towing a 5000lb trailer. Stability was great, but the unhitched ride quality was rough. I moved to LT-Cs (Goodyear Wrangler SilentArmor A/T) and the towing stability was still great, but the unhitched ride quality was quite significantly improved.


Posted By: fleetprowl on 05/18/10 11:58pm

I tow our 6,750 lb. 5th wheel with P rated tires on my '06 chevy 1500. I use my truck much more as a daily driver than as a tow vehicle. I like the non towing ride much better with P rated tires than LT rated tires. Plus, I've never had a problem with the P rated tires while towing. The max pressure on my BF Goodrich Long Trail T/A's is 44 lbs., not 35 lbs.






Posted By: 12thgenusa on 05/18/10 08:32am

My truck came with P metric tires also. I towed with them until they wore out and then replaced them with LT tires. I didn't notice any ill effects while towing with the P rated tires. I did run them at the max 35 psi sidewall pressure. The ride and handling quality probably has as much to do with the quality of the tire as it does with the "P" or "LT" rating.


Dave & Gean

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Posted By: BenK on 05/17/10 12:26pm

Agree and exacerbated by the weaker sidewalls (that marshmallow ride), which then
has more flexing, which then has more heat built up

One a tire has be degraded by whatever, it will NEVER be the same. It is cumulative.

This is a good thread by Tireman9 Tire condition Examples


Not many understand, nor believe that running a tire underinflated can create
enough heat to melt the ply cords like this:


That is part of why it is cumulative. Not just the cords, but also the rubber
compound (rubber is only a fraction of the material these days...petrol chem
based is the majority now)


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Posted By: BenK on 05/17/10 12:43pm

To the PMs...

Posted many times and again here

There are basically three classes of tires for our TVs.

Lowest is 'P' rated (aka...passenger) tires.

Next higher class is 'LT' rated (aka...light truck) tires

Next higher class is 'commercial' (aka...semi's)

There is a sub class in the 'LT' class. That is for trailer tires, 'ST' and
have a generic speed rating of 65 MPH and have read here that some are rated
75 MPH, but I've not confirmed that for myself.

'P' or passenger car tires used on our Light Trucks, there is a need to de-rate
the sidewall weight rating by 9%-10% when used on light trucks. All or most all
~7K GVWR trucks (half ton) come from the factory with 'P' rated tires, they have
already been de-rated by the OEM design team. That size will have that factored in

Am not saying one is bad and the other good. Just that they have different attributes

I have 'P' rated tires on all of my 'cars' and my mini van. ON all of my trucks,
even 'half ton' trucks have 'LT' tires. They came with 'P' rated, but again I
change them the first chance I get. That is my preference.


Posted By: BenK on 05/17/10 10:32am

A few more listing the 9%-10% de-rating range. There are more, but only listed two.
One is from our watch dog agency (NHTSA/DOT) and other is from a tire OEM


DOT 49 CFR Part5, Federal Motor Vehicle Safety Standards; Tires
An old rule reviewed in 2000 and kept according to this report. All
about safety and safety margin (they use 'reserve'). Both in the initial
design rating of the OEM listed for 'that' vehicle and generically for
any 'P' rated used on trucks

Nitto tire on P vs LT tires for trucks

This is just weight carry, but there is more to towing than just weight

The 'stiffness' and/or resistance to sidewall fold over is a key metric
to towing.

Two tires from the same OEM, same model, same size, etc will have the
LT tire weigh more and cost more than a 'P' rated (class) tire.

Most or at least all that I've come across that prefer 'P' over 'LT'
tires weigh 'ride quality' higher than most anything else to do with
their tire choice. 'Ride quality' is NOT on my 'have to have list'
and it is at the bottom of my 'nice to have' list of attributes.

From an engineering or automotive enthusiast point...wonder what they
found during their testing that required them to de-rate 'P' class
tires for trucks?


Posted By: beemerphile1 on 05/17/10 11:01am

BenK wrote:


..From an engineering or automotive enthusiast point...wonder what they
found during their testing that required them to de-rate 'P' class
tires for trucks?


Only a guess but since trucks generally sit higher than a car there will be more roll stress on the tire. Think of all the problems with the Ford Explorer a few years ago.

OP, the P tires will do fine as long as you enjoy the feel of riding on marshmallows. I would also suggest that you weigh your 5er. Manufacturers dry weights are notoriously understated. You very well could exceed your ratings particularly the pin weight on the rear axle. Never, ever trust the manufacturers numbers.


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Posted By: JIMNLIN on 05/16/10 07:04pm

This gets posted all the time especially in the trailering forums.
DOT regs;

S4.2.2.2 When passenger car tires are
installed on an MPV, truck, bus, or
trailer, each tire’s load rating is reduced
by dividing it by 1.10 before determining,
under S4.2.2.1, the sum of
the maximum load ratings of the tires
fitted to an axle.

More input from the Tire Rack web ;
tire rack

Part of Tire rack info ;
.......(snip) "a Euro- or P-metric tire designated to carry 2,000 pounds on a car is restricted to carrying 1,820 pounds when used on a van, pickup truck or SUV."


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