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 > Tire aspect ratio

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blt2ski

Kirkland, Wa

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Posted: 03/24/22 07:10am Link  |  Quote  |  Print  |  Notify Moderator

I had 245-75-16 lr E tires stock on an 88, 96 K3500's. I went to a 265-75-16 LR D. Those handled towing, hauling etc better than the 245's. So a rig with a lower ply rating is not an absolute worst option. The 265's in reality had a whipping 40 lbs less capacity.
Later the D rated tires were discontinued for R rated tires at 3400 per vs 3000. For my use, usually no higher load in RA in the upper 5500-6000 range. No difference between the two.
On my 1500, I only have 35 lbs in the 285-65-18 tires on it. I could only get LR E in this size. I don't use but 1/2 if the tire capacity. In my case aP or XL/LR C rating would work just fine!
No matter the truck size, you need to get the load capacity rating in the tire size you want to run. So like my 3500's going from an E to a D was not an issue.
Also make sure your rims are wide enough if you go to a wider, or higher aspect tire. That also makes a difference in handling.

Marty


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MNRon

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Posted: 03/24/22 07:14am Link  |  Quote  |  Print  |  Notify Moderator

You definitely want LT's. It may be possible to change sizing slightly, google 'tire calculator' and you can understand the difference between sizes and may find a similar size that fits and doesn't change your odometer etc


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Grit dog

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Posted: 03/24/22 07:57am Link  |  Quote  |  Print  |  Notify Moderator

Another train wreck of mis information, over explanation and stories about that “one time I….”
Do you all have ADD???

OP, you found cheap tires that are P rated and 114 load rating. This is obvious by the load rating. There is no further question. You have confused yourself about tires.
Use a tire that is rated properly for the vehicle it is to be installed on. Pick the size pick the brand pick white letters or not, but don’t install anything with less than a 121 load index.


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bob213

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Posted: 03/24/22 11:32am Link  |  Quote  |  Print  |  Notify Moderator

You can change tires as long as they fit and have the capacity that you need. I found that most nationwide tire dealers will not install a tire that is more than one size large than stock. Here's a comparison tool that will show you size difference.
Tire size calculator


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Cummins12V98

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Posted: 03/24/22 03:49pm Link  |  Quote  |  Print  |  Notify Moderator

Grit dog wrote:

Another train wreck of mis information, over explanation and stories about that “one time I….”
Do you all have ADD???

OP, you found cheap tires that are P rated and 114 load rating. This is obvious by the load rating. There is no further question. You have confused yourself about tires.
Use a tire that is rated properly for the vehicle it is to be installed on. Pick the size pick the brand pick white letters or not, but don’t install anything with less than a 121 load index.


Folks that's that!!!


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agesilaus

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Posted: 03/24/22 04:02pm Link  |  Quote  |  Print  |  Notify Moderator

I was somewhat confused but aware that something did not seem to be right. Which is why I asked here in the first place.
However I will disagree about the 'cheap tires', these Michelin's are over $350, the Escapee discount knocks $105 off the price making them look cheaper.
I was hoping for a combination of Michelin road reputation, and occasional off road driving. Especially looking for that extra mpg that Michelin has a reputation for in these parlous times.


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Sport45

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Posted: 03/24/22 08:52pm Link  |  Quote  |  Print  |  Notify Moderator

Michelin is a bit deceptive with the name of this tire. The LT in LTX doesn’t mean anything as “LTX” is just the name of the tire, no different than “Wrangler”, “Discoverer”, or “AT3”. As mentioned above, go by the load index and look for LT preceding the section width on the tire size.


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BenK

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Posted: 03/24/22 09:28pm Link  |  Quote  |  Print  |  Notify Moderator

Maybe folks will accept this link to TireRack’s page on P vs LT class tires and the reference to the RMA recommendation of de-rating P class min 9% when used on pickups & SUVs

LOAD REDUCTION OF EURO- & P-METRIC TIRES ON LIGHT TRUCKS

edit...fixed clicky https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=70

tirerack wrote:

When it comes to selecting replacement tires for a van, pickup truck, crossover and SUV, the most important consideration is to maintain sufficient load carrying capacity.

Three tire-sizing systems are used on the Original Equipment (O.E.) tires fitted to today's light trucks, Euro-metric, P-metric ("passenger" metric) and LT-metric ("light truck" metric). Many 1/4-ton and 1/2-ton vehicles use Euro-metric and P-metric sized tires, while 3/4-ton and 1-ton vehicles use LT-metric sized tires.

Euro-metric and P-metric tire sizes were originally designed for cars and station wagons; however, they have also been used for light truck applications because most vans, pickup trucks, crossovers and SUVs are used to carry passengers, not cargo. Additionally, most of the new light trucks being produced today are equipped with Euro- or P-metric sized tires because they offer lighter weight, lower rolling resistance and less aggressive tread designs (which makes them better riding, more fuel efficient and less noisy) than typical heavy-duty tires.

However, there is an idiosyncrasy governing the use of Euro-metric and P-metric sized tires on vans, pickup trucks, crossovers and SUVs because these vehicles have a higher center of gravity and greater probability of being overloaded than passenger cars. In order to accommodate this, vehicle engineers are required to specify Euro- or P-metric sized tires rated to carry 10% more weight than would be required if they were used on a passenger car. This is the equivalent of taking the tire's load capacity branded on its sidewall and dividing it by 1.1. For example, a Euro- or P-metric tire designated to carry 2,000 pounds on a car is restricted to carrying 1,818 pounds when used on a van, pickup truck, crossover and SUV. This size selection practice provides the vehicle manufacturer with the appropriate tire load capacity.

On the other hand, LT-metric sized tires were specifically developed for use on light trucks and provide the full tire load capacity branded on their sidewall. They are the little brothers of the heavy-duty tires fitted to 18-wheelers and buses, and use the same basic engineering guidelines regarding load capacity. Because of this, LT-metric sized tires are built very strong, and use higher inflation pressures to carry a given load in order to provide the desired safety margin. You really don't want the tires of the 18-wheeler alongside you on the interstate running at the limit of their endurance, do you?

While there isn't a problem determining an appropriate alternate size when replacing Euro- or P-metric tires with other Euro- or P-metric sizes, the differences in load capacity and required inflation pressure prohibits mixing the LT-metric tires with Euro- or P-metric tires, as well as often prevents replacing sets of Euro- or P-metric tires with dimensionally equivalent LT-metric tires, and vice versa.

Selecting the correct tire size will help ensure you have the performance and long term durability you desire.


* This post was edited 03/24/22 10:15pm by BenK *


-Ben Picture of my rig
1996 GMC SLT Suburban 3/4 ton K3500/7.4L/4:1/+150Kmiles orig owner...
1980 Chevy Silverado C10/long bed/"BUILT" 5.7L/3:73/1 ton helper springs/+329Kmiles, bought it from dad...
1998 Mazda B2500 (1/2 ton) pickup, 2nd owner...
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Grit dog

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Posted: 03/25/22 08:03am Link  |  Quote  |  Print  |  Notify Moderator

^Great, but the OP needs LT tires.
PS , I’ve heard the de-rating nonsense on here for years. It’s laughable. Akin to 1800lb payloads in 3/4 ton trucks. Just regulatory nonsense.

MFL

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Posted: 03/25/22 12:06pm Link  |  Quote  |  Print  |  Notify Moderator

Go Grit...right on, even 3/4 example! While de-rating, of wrong tires, can be needed, why bother, just get the proper tires, and done.

Jerry





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