Tires - Need some help understanding load, etc..

[Nado]

Hello all. I recently upgraded from my 4th gen 1500 or a 5th 2500 Laramie CC. I am looking at tossing the twentys that came on the truck, and order up a set of 17x9.5 with 35x12.5 rubber.

But, I understand the HD trucks carry a different load rating with their tires. I am looking to run a good A/T tire like Mickey Baja or Wildpeaks. My question is....do I need to get a F load rated tire, or E? 8 ply vs 10 ply?

If I ran an E rated tire, will the dash be constantly telling me my pressure is low? I do have Alpha OBD, so I could probably find a setting for that.

Any education on this is appreciated!

Thanks,
Nathan

 

[OC455]

The 20inch tires that are on your truck are E rated (125 load index). If you are going to a 17 inch tire and run 35x12.5's, it will still be an E rated tire but most of those tires have a lower load index 121. Only 2 tires in that size are 125 load index which are a Toyo MT and the Nitto Mud Grappler.

You shouldn't have an issue with TPMS if the sensors are set right.

 

[lpennock]

If you haven't ordered tires and rims yet, go with 35x12.50-18 instead. 17s are limited to 3195lb (121) except some grandfathered designs. 18s can go as high as 4030lb. You can get tires that won't reduce your load rating like 17s do.

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[14hemiexpress]

Second What’s already been said check the load index rating. 125 is oem. I don’t remember at what pressure the tpms will go off at but I run 65-70 in my fronts and it hasn’t tripped on me yet.

 

[loveracing1988]

Second What’s already been said check the load index rating. 125 is oem. I don’t remember at what pressure the tpms will go off at but I run 65-70 in my fronts and it hasn’t tripped on me yet.

The light will kick on at 80%, so 64 rear and 52 front.

 

[oe542bob]

I see you are in Tennessee so maybe this won’t affect you. On my 2500, I wanted to go to 305/50/20s. Right load rating, but when I was told at the dealership that they wouldn’t be passable for inspection here in PA. I said they are the correct load rating and I was told that the outside diameter was a little smaller and that’s why it’s not passable. It was only like a 1/4” different. I would be allowed to go a little bigger, but not smaller.
Ended up going to a 295/60/20 Nitto G2. This information may not apply to your state, but maybe it does, so check it out.
Plus, make sure 17’ rims will fit over your brake calipers. 18” should work as the 2500 did come with that size rim.
Good Luck.

 

[Nado]

If you haven't ordered tires and rims yet, go with 35x12.50-18 instead. 17s are limited to 3195lb (121) except some grandfathered designs. 18s can go as high as 4030lb. You can get tires that won't reduce your load rating like 17s do.

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Can you elaborate on the load rating a bit? Is it as simple as it reads? Aka, the 121 rating means the truck can only handle 3195lb in total payload?

 

[Nado]

Second What’s already been said check the load index rating. 125 is oem. I don’t remember at what pressure the tpms will go off at but I run 65-70 in my fronts and it hasn’t tripped on me yet.

So most e rated tired have a max fill psi of 55-65psi. How are you running 70psi? I presume you have larger diameter wheels that 17?

 

[WoodGuy]

I'm no tire expert, but have had 3/4-1 tons all my adult life (Contractor) , all have had E rated tires and most called for 80 psi from the manufacturer

 

[Nado]

I'm no tire expert, but have had 3/4-1 tons all my adult life (Contractor) , all have had E rated tires and most called for 80 psi from the manufacturer

This is why I was questioning pressure. I have always seen this lineup on tire manufacturers sites....

 

[14hemiexpress]

So most e rated tired have a max fill psi of 55-65psi. How are you running 70psi? I presume you have larger diameter wheels that 17?

it depends on where you look. You gotta go by the manufactures ratings. I have seen F rated tires that max 80 I have seen E max 65. I even had a set of D rated Ko2s that were rated to 65. The E rated tires that have the lower 65psi rating are the lower load index ones. When buying a tire look for the load index then look at the psi rating. Just because it’s class E or F doesn’t just automatically right or wrong it just determines the ply.



edit: after quick research I couldn’t find a single 17in that had higher load rating than 121. If you stepped up to a 18 and ran a 325 65r18 you would get about 34.6x13 you could also drop to a 295 70r18 and get 34.3x11.75 both sized tires gets you high enough load rating for your truck.

 

[Nado]

it depends on where you look. You gotta go by the manufactures ratings. I have seen F rated tires that max 80 I have seen E max 65. I even had a set of D rated Ko2s that were rated to 65. The E rated tires that have the lower 65psi rating are the lower load index ones. When buying a tire look for the load index then look at the psi rating. Just because it’s class E or F doesn’t just automatically right or wrong it just determines the ply.

View attachment 245135

edit: after quick research I couldn’t find a single 17in that had higher load rating than 121. If you stepped up to a 18 and ran a 325 65r18 you would get about 34.6x13 you could also drop to a 295 70r18 and get 34.3x11.75 both sized tires gets you high enough load rating for your truck.

Thank you. Learning rather quickly about load rating, etc... This helps dramatically. While I like the look of 17s, I might have to have 18s, because I dont really want to give up payload just in case. Looking at my current 20' Toyo Open Country A/T wheels they an E rating with an 80psi max pressure and higher loan index. It seems that 17s wont support near that level. So, I may have to go 18s.

Again, this really helped. Appreciate it everyone.

 

[OC455]

Can you elaborate on the load rating a bit? Is it as simple as it reads? Aka, the 121 rating means the truck can only handle 3195lb in total payload?

The load index rates the tire and how much weight it can carry per tire. So a load index of 121 means each tire can carry 3195lbs per tire. So two tires would be able to carry 6290lbs.

With my dually the front tires at 80psi are rated for 120 load index on the front. So that's 3086lbs per tire. 6172lbs. for the two tires on the front. At 65psi for the four tires on the back, the load index rating is 117, which is 2892lbs of load carrying per tire, x4 is 11,568lbs for the back of the truck. So in total, my tires can carry 17,740lbs. IT doesn't mean that the truck can...so before a certain individual comes here and makes a post saying a higher load index tire that doesn't exist will give you the ability to carry & tow more, IT DOES NOT.

Same tires, two different load index ratings 120/117 for the same tires at different tire pressures that they are rated for. Other tires depending on size do not have a dual load index rating.

On my 1500 I went with a XL rated tire that had a load index of 116. The OEM tires were the Goodyear SR-A's that had a load index of 114. Did it mean I could carry more, no, the higher load index tire and the XL rating just made the truck handle better when towing and carrying any cargo. Most guys do this to get better handling or stability from their truck..

 

[lpennock]

Tires with 2 ratings like 120/117 has nothing to do with pressure, it is single vs dual fitment. In a dually usage the tires have a 10% derating. This derating is because it is impossible to have exact same load all the time on each tire. So if you are buying the tire for a front on single rear application you use the larger number and for duals you use the smaller number.

Tire letter load ranges to maximum pressure depends on.the type of tire. That is normal vs flotation sizes not AT vs MT. Metric LT below 305 are normal and 305 and bigger plus height x width tire are flotation. Flotation tires run at a lower pressure for the same letter size. Here is pressures for the D an E ratings.
E 65 vs 80
D 50 vs 65

A E121 is rated for 3195 at 80 psi for a normal size and at 65psi for a flotation size. People think the 80 psi tire has less sway but load carry ratings is exactly the same. General rule of thumb is a flotation size will give a smoother ride while the normal non-flotation size will have less sway at the same overall height. A 121 rating carries the same 3195 regardless of it being an E or D, 17 o 18 or 20.

Going back to the comment about 17s being limited to 3195lb. TRA will not approve any new 17" tire designs rated above 3195lb. There are existing tires that are grandfathered and rated higher. If the get a redesign the will be limited to 3195. Check Toyo AT vs AT2 and later and you will see thisl



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[Nado]

The load index rates the tire and how much weight it can carry per tire. So a load index of 121 means each tire can carry 3195lbs per tire. So two tires would be able to carry 6290lbs.

With my dually the front tires at 80psi are rated for 120 load index on the front. So that's 3086lbs per tire. 6172lbs. for the two tires on the front. At 65psi for the four tires on the back, the load index rating is 117, which is 2892lbs of load carrying per tire, x4 is 11,568lbs for the back of the truck. So in total, my tires can carry 17,740lbs. IT doesn't mean that the truck can...so before a certain individual comes here and makes a post saying a higher load index tire that doesn't exist will give you the ability to carry & tow more, IT DOES NOT.

Same tires, two different load index ratings 120/117 for the same tires at different tire pressures that they are rated for. Other tires depending on size do not have a dual load index rating.

On my 1500 I went with a XL rated tire that had a load index of 116. The OEM tires were the Goodyear SR-A's that had a load index of 114. Did it mean I could carry more, no, the higher load index tire and the XL rating just made the truck handle better when towing and carrying any cargo. Most guys do this to get better handling or stability from their truck..

So going with a 121 loan rating may not decrease my Payload capacity, necessarily?

 

[lpennock]

What does your door tag say for GAWR Rear? Take that number, divide by 2. If result is greater than 3195 a 121 will reduce your your payload. If it is less than 3195 a 121 will not reduce your payload.

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[OC455]

So going with a 121 loan rating may not decrease my Payload capacity, necessarily?

Load Range / Ply Rating Identification | Tire Rack :

In all cases, when changing tire sizes or converting from one type of size to another, it is important to confirm that the Load Index in the tire's service description of the new tire is equal to or greater than the Load Index of the original tire and/or that the new tire's rated load capacity is sufficient to carry the vehicle's gross axle weight ratings.

"The load range/ply rating branded on a tire's sidewall identifies how much load the tire is designed to carry at its industry specified pressure."

 

[Nado]

Load Range / Ply Rating Identification | Tire Rack :

In all cases, when changing tire sizes or converting from one type of size to another, it is important to confirm that the Load Index in the tire's service description of the new tire is equal to or greater than the Load Index of the original tire and/or that the new tire's rated load capacity is sufficient to carry the vehicle's gross axle weight ratings.

"The load range/ply rating branded on a tire's sidewall identifies how much load the tire is designed to carry at its industry specified pressure."

Only problem I have is this vehicle came with fuel 20s and aftermarket tires...not factory tires. So I'm not sure of what the initial design was. So I have to just go off of what is on my truck now.

 

[14hemiexpress]

Only problem I have is this vehicle came with fuel 20s and aftermarket tires...not factory tires. So I'm not sure of what the initial design was. So I have to just go off of what is on my truck now.

your door sticker should have your oem size. You can put that into discount tire, tire rack etc and it usually will pop up a OEM tire. On the newer rams they are Firestone tires, and on the 20s it will be a 285 60r20 with a load index of 125.

 

[Nado]

What does your door tag say for GAWR Rear? Take that number, divide by 2. If result is greater than 3195 a 121 will reduce your your payload. If it is less than 3195 a 121 will not reduce your payload.

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Awesome. Thank you. Looks like I'm gonna not lose any.