Looking into tires again and I am noticing a trend to move away from Load Range and into Load Index.

Load Rating --- Based on ply rating alone

E = 10 ply tire
D = 8 ply tire
C = 6 ply tire

Load Index --- Is not contingent on ply rating alone. The rating is for the load capacity of the tire at it's maximum pressure.

Let's take BFG A/T for an example in two sizes that are popular for our trucks.

LT285/70R17 - load range E -10 plies - Load Index 121 = 3197 lbs @80psi (which BFG rounded to 3195)

LT315/70R17 - load range D - 8 plies - Load Index 121 = 3197 lbs @50psi

Notice the Load Index is the same for both tires and both are capable tires on our trucks for a loaded max weight of 9591lbs.

Let's look at the Nitto Trail Grappler for the next example.

LT285/70R17 - load range E - Load index 121

LT315/70R17 - load range D - Load index 121

35x12.5R17 - load range E - Load index 121

As you can see the 35 and the 315 have the same capacity for the same relative size tire in two different load ranges. My point is this, I would advise when tire shopping to pay more attention to the Load Index then Load Range.

Dynapro MT

LT285/70R17 index 121
LT315/70R17 index 121
35x12.5R17 index 124 <- Best I've seen in a 35 or 315

The index Rating will give you a better representation of what the tire can actually carry then by just going by load range alone. One common argument I hear is that an E rated tire is a must for towing. I'm on the fence about this one. I can believe that 10 plies would give the tire a stiffer sidewall but then we have to take in consideration that not all plies are created equal. What if the 10 plies are substantially weaker then the 8 ply tire next to it? Think of ST trailer tires, I have seen 6 ply tires that make any of these 10 ply tire's sidewalls look like tissue. /rant I'm "tired", going to bed....




100 to 150
Load
Index (lbs)
100 1764
101 1819
102 1874
103 1929
104 1984
105 2039
106 2094
107 2149
108 2205
109 2271
110 2337
111 2403
112 2469
113 2535
114 2601
115 2679
116 2756
117 2833
118 2910
119 2998
120 3086
121 3197
122 3307
123 3417
124 3527
125 3638
126 3748
127 3858
128 3968
129 4079
130 4189
131 4289
132 4409
133 4541
134 4674
135 4806
136 4938
137 5071
138 5203
139 5357
140 5512
141 5677
142 5842
143 6008
144 6173
145 6393
146 6614
147 6779
148 6844
149 7165
150 7385

 

A tire that can only handle 50 psi doesn't say much about sidewall integrity to me,no matter what the load index. I used them once got too many flats and then a near catastrophic blowout.
E's since with stellar results.
I guess I'm old school.
Firestone/Bridgestone is the only E-rated 315-70-17 I'm aware of.

 

Plys aren't created equal, that's why it's called a "ply rating". The actual number of plies isn't counted, it's the relative strength of the plies together which are then indexed, giving you the "ply rating".

If you count the actual number of plies, you'll find that it's significantly fewer than what the "rating" implies.

The ply rating is loosely related to load index (actual weight capacity). It's really a measure of relative sidewall stiffness, which is why tires are labeled with both the load index and ply rating...one or the other doesn't tell us what we need to know about the tire.

 

Awesome for pointing that out. The Load Rating, I think, was developed as a way to compare the new radial tire against the standard bias ply tire back in the day. So a E rated tire had the same general load capacity of a 10 ply bias tire.


The actual ply construction should be marked on the sidewall of the tire.

 

Sure thing,but I'm still not comfortable with a 50 psi tire. I've got a friend who scores 315 BFG's cheap. His truck weighs 10,500# with utility bed and Callen camper. Riding behind him,his sidewalls are way too buldged out. In Baja he's experienced sidewall failure aired down,in contrast to my other friend with a similar setup. Friend #2 runs E-rated Toyos and has not had issue one.
Unladen trucks I don't think would be an issue.
A guy yesterday at a shop I use had some 37-13.50 18 Toyo MT's mounted. They've got a whopping 3550# D-rating.
A 37-13.50-17 has an E-rating. It has the next notch up weight capacity.

 

eight ply tires to ten ply tires is a night and day difference..

theres a reason why these trucks come with 10 plies from the factory, tread ply IMHO is of little concern.. its the sidewalls that id worry about... the more sidewall plies, the better the tire...

ive ran both, eight and ten ply tires on my trucks, and I don't like the marshmallow ride that the 8 plies provide, and several flats later.. nope.. back to ten plies I went... and so far.. trouble free.....

 

I towed my 23-foot (10k lb) toy hauler on D-rated Yokos, 315/70-17. It's a 50 psi tire.

They did ok, but wouldn't want to go any heavier on them.

So when I got my current fiver, a 42-footer, 17k lbs, I stepped up to an E-rated Toyo MT, 35x12.5x17.

I do a lot of off-roading, and D-rated tires are great in sand because they bulge-out when aired down. I can let all of the air out of my E-rated Toyos and I don't think they'd bulge at all LOL

 

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I agree with TxDiesel007! There is a big difference between an 8ply and 10ply tire for our trucks!

I also am VERY particular about the brand name now since so many tires are being in China. Personally, I have only run either "BF Goodrich" or "Michelin"
or "General" on my Dodge CTD Pickups since 1991 with excellent service and
reliability.

 

It's worth mentioning that stiffer sidewalls not only mean more strength and resistant to flats, they generally have better MPG (lower rolling resistance) and worse ride quality.

I'm running the 315 Duratracs, which are E rated in 315/75/16

 

I guess I'm old school as well.... I can't see a "D" rated tire handling the same as an "E" rated tire when running at or close to max GAWR on a 3/4 or one ton single rear wheel truck.

If your never loaded, "D" tires may make sense. When your loaded (in my case over the GAWR with the camper on) it isn't worth the gamble going with "D" tires...

 

8 ply tires don't last around here even empty. Boss' 02 had 315's, D-rated, when he got it, after a couple months use I had to use it to feed some bales one day, and ended up having to change a tire because I couldn't plug it fast enough to stop the leaks. Thing was perforated.

 

I know one thing, if I ever go back to a 1/2 ton it will be wearing E rated tires! Not for the weight rating but it's a tougher tire than can handle a lot of abuse.

 

I've had good luck with my D rated Deans as far as mileage goes, but for towing they aren't handling as well as my retired E rated one's.

I'll replace with E's next time....

 

Going to get some 275/70/R18 Nitto Terra Grapplers Load Range E on Sunday.
Birthday present from my awesome wife. The M/T MTZ still have some life left but wont stay balanced. Put about 55,000+ on them anyway.

 

Just an update, Night and Day difference over the MTZ tires, man I love these Nitto's.