Load Range vs Load Index?

[AK4900PA]

Truck is a '18 Ram 2500 CTD

I currently have 37x12.5r20 that have a F load range with a 128 load index.

Stock tires were 275/70r18 that had a E load range with a 125 load index.

For my next set I'm looking at going up to a 38x13.5r17 with a D load range and 127 load index.

With the load index being higher than stock is the D load range going to be an issue other than possibly less mileage?

The truck has never towed anything heavier than a log splitter (~800lb) and it hauls a yard of top soil for the wife's garden about 10 miles once or twice a year.

 

[KKBB]

If you aren't hauling anything other than what you say, it should be just fine. If you were towing weights that the Cummins is designed to tow, I wouldn't have a D rated tire on there, but then I also wouldn't have 38's on there either...haha. You should be good IMO.

 

[chopperman1]

Biggest thing you'll see is more side to side movement, ie in corners, bumps in the road etc. The D's have softer sidewalls. Next issue is your TPMS. Pressures are much lower in D tires vs E. You can change the settings for the TPMS with AlfaOBD or similar.

 

[62Blazer]

Load index 125 = 3,638 lbs. per tire
Load index 127 = 3,858 lbs. per tire
Load index 128 = 3,968 lbs. per tire
Basically the 127 tire has a higher weight capacity than the factory tires, and only 110 lbs. per tire (440 lbs. total) less than what you have now. Don't really see the problem and the 4 tires combined are rated to carry over 15,000 lbs. of vehicle which is way, way more than what you need.
The "load index" gives an exact weight capacity of the tire regardless of the size.....if a tire has a load index of 125 is can support 3,638 lbs. regardless of the tire size. The "load range" of a tire is also dependent on the tire size.....meaning that a load range E rated tire will have different weight capacities depending on the size. Typically if you take an E rated tire the larger the size the higher the actual weight capacity is.
For example on a Nitto Ridge Grappler
33x12.50R17 E rated = 3,085 lbs.
Go to the next size bigger and the weight capacity goes up
35x12.50R17 E rated = 3,195 lbs.
Now look at a larger size tire that is only D rated
37x12.50R17 D rated = 3,585 lbs.

In general tire manufacturers are starting to go more by load index versus the older C, D, E, etc... load ratings simply because the load ratings can be a little deceiving since the weight capacity varies by size where the load index always gives the same number.

 

[Bike_Pilot]

I think the 127 index tires will be just fine, especially with that your use case. I run 128 index 37s and they worn great for me and your setup won't be much different in think. There is probably more difference from one tire model to another than from 127 to 128 index.

 

[mtofell]

In general, it's incorrect practice to down-rate your tires and some shops won't do it. Of course, it's your truck and you're free to do whatever you like but it is kind of a shame to have a beast of an engine and truck that isn't capable of using it's potential.

 

[62Blazer]

In general, it's incorrect practice to down-rate your tires and some shops won't do it. Of course, it's your truck and you're free to do whatever you like but it is kind of a shame to have a beast of an engine and truck that isn't capable of using it's potential.

They are wanting put on tires that have a higher load index, thus have a higher weight rating, than what the factory tires were? Though I will say if towing and hauling were the main priority they probably wouldn't want 38's....but that doesn't seem to be a concern.

 

[mtofell]

They are wanting put on tires that have a higher load index, thus have a higher weight rating, than what the factory tires were? Though I will say if towing and hauling were the main priority they probably wouldn't want 38's....but that doesn't seem to be a concern.

Guess I should have read your entire previous post

I just saw "D" and assumed it was less weight. I didn't realize that was possible.