Load range C vs D - help me understand why D is suggested?

[driventoadventure]

Now that I have my lift, I am trying to figure out my tires, and debating between 35 and 37 mostly as a function of cost (not excited to have to buy new wheels right now). I found Discount Tire has some Load Range C 37" KO2 KO3 (Whoops, typo) for about $125 less than the load range D or the rest of the 37" tires. My thought is that I should prefer load range C because they'll be more flexible, and therefore better for traction and the ability to flex around rocks etc will outweigh the two fewer plies of rubber. I do about 60/20/20 percentages highway/city/off-road rock crawling (about 1/3 of that highway or 20% of total driving includes towing a trailer).

Is my thinking that dramatically wrong? Am I missing something? If I am trying to just moderate my cost, am I better off just getting 35s on the factory wheels for now and then upgrading to 37s and new wheels when the 35s wear out?

I still have a enough of mileage left on my factory 33s to last the summer, so this is more about capability upgrade right now, but I suspect that I will want to get new tires before the snow of this coming winter.

(e) fixed a typo, the LR-C are KO2.

Sponsored

 

[Themistocles]

I had exactly that same dilemma that I just came to conclusion on and went with the D range.

My reasoning.

First...most important reason for me. Death Wobble. I have heard nobody talk about sidewall stiffness and death wobble on the Jeep forums. However, it was a substantial topic of conversation regarding my other vehicle....a 2500 Ram CTD....and my previous vehicle a 2500 Ram 8.0L. In my 8.0L Ram, since I used it mostly for lightly loaded driving or cruising back roads in Montana and Wyoming, I figured...WTH go with C Range...less cost, more comfortable ride. A few thousand miles later experienced my first DW event. Chased it with parts for a while...didnt fix it. Finaly took it in to a very experienced diesel mechanic with experience on a couple Baja and Best in the Desert teams. He took one look at it and, as if speaking to a 5 year old, explained my problem was the flexy sidewalls. I listened and switched to load range E tires ... never had DW in that truck again. Was that Ram significantly heavier than my Jeep, yes. But a JLURD is not exactly a featherweight. I have already cured DW once in this Jeep. I figured why take the risk.

Second...the C range tires you are referring to have a decent amount less tread depth than the D range. Probably not that big a deal, but tread depth impacts both traction and tire life.

Third...the thinner tire of the C range, especially the sidewalls, is just not as durable. It may realistically mean very little, but as I am listening to the sidewall of my tire grab a big rock as I try to squeeze through some place, or use my sidewall grip to climb a notch, I am more comfortable with a little more heft.

Downside...high load range, more weight...more weight equals more rotational force means more wear on parts.

 

[4xFUN]

Know nothing about the new KO3's...
But I can offer my two cents on the KO2 37x12.50R17 'C' vs 'D' as I have had both. I started out with going from 315's (35) to the new at the time KO2 37' C but within days had Discount Tire switch the C's out to D's and could not be happier. What I did not like about the 37 C's was the fact that the tread was narrower than both the 315's and the 37 D's, a good 5/8" to 3/4" difference! Also I didn't like the way they handled-a little too 'squishy' in the corners and my JLR just did not seem as 'planted' as it did on the 315's. Installed the 37 D's and was much happier with both the looks (tread wider and flatter) and the way my JLR handled.

37" 'C':

37" 'D': Between 5/8" and 3/4" wider tread...

 

[azwjowner]

Most people overlook that for tires wider than 11.5", the load range max PSIs are different and lower. C becomes 35 instead of 50, D becomes 50 instead of 65, and E becomes 65 instead of 80.

So your wide D load tire doesn't really have stiffer sidewalls than a normal C tire.

 

[driventoadventure]

Know nothing about the new KO3's...
But I can offer my two cents on the KO2 37x12.50R17 'C' vs 'D' as I have had both. I started out with going from 315's (35) to the new at the time KO2 37' C but within days had Discount Tire switch the C's out to D's and could not be happier. What I did not like about the 37 C's was the fact that the tread was narrower than both the 315's and the 37 D's, a good 5/8" to 3/4" difference! Also I didn't like the way they handled-a little too 'squishy' in the corners and my JLR just did not seem as 'planted' as it did on the 315's. Installed the 37 D's and was much happier with both the looks (tread wider and flatter) and the way my JLR handled.

37" 'C':

37" 'D': Between 5/8" and 3/4" wider tread...

Now THAT is very interesting that the tread was wider based on load range.

 

[RicRecon]

I drive a 21 JKUR Diesel and went with D size Toyo RT Trails in 315 size primarily due to the weight of this Jeep and that I regularly tow a small off-road trailer (approx 2k lbs) and I wanted that additional assurance. I can say that regardless of whether I’m towing, off road or on, or not towing, off road or on, my Jeep rides much better on these tires than the stock KO2s

I do find the above post about D size 37 KO2s being wider than the C size very interesting and I’ll keep that in mind in the future.

 

[azwjowner]

Now THAT is very interesting that the tread was wider based on load range.

I am not in the camp of BFGs run small in general, but whenever you have a size created specifically for an OEM (like the 315/70/17 load C and the 37x12.5 load C were, for Jeep and Ford), it seems they always make them as small as possible to maximize fuel economy.

 

[4xFUN]

I am not in the camp of BFGs run small in general, but whenever you have a size created specifically for an OEM (like the 315/70/17 load C and the 37x12.5 load C were, for Jeep and Ford), it seems they always make them as small as possible to maximize fuel economy.

When it comes to the 37" C, you are right-Ford mandated a maximum weight while maintaining the height and overall section width of the 37" D...One way to help achieve this was to take a bit from tread width.

The 315/70R17 KO2 C are wider than the the 37" C and I think an ideal all-round tire, especially for a JLR...

 

[Old Jeeper]

Now that I have my lift, I am trying to figure out my tires, and debating between 35 and 37 mostly as a function of cost (not excited to have to buy new wheels right now). I found Discount Tire has some Load Range C 37" KO2 KO3 (Whoops, typo) for about $125 less than the load range D or the rest of the 37" tires. My thought is that I should prefer load range C because they'll be more flexible, and therefore better for traction and the ability to flex around rocks etc will outweigh the two fewer plies of rubber. I do about 60/20/20 percentages highway/city/off-road rock crawling (about 1/3 of that highway or 20% of total driving includes towing a trailer).

Is my thinking that dramatically wrong? Am I missing something? If I am trying to just moderate my cost, am I better off just getting 35s on the factory wheels for now and then upgrading to 37s and new wheels when the 35s wear out?

I still have a enough of mileage left on my factory 33s to last the summer, so this is more about capability upgrade right now, but I suspect that I will want to get new tires before the snow of this coming winter.

(e) fixed a typo, the LR-C are KO2.

THe real question is: Are you are rock crawler or not? If not go with the "C", if you are a Moab rock guy, go with "D" and you will be glad you did...

 

[driventoadventure]

THe real question is: Are you are rock crawler or not? If not go with the "C", if you are a Moab rock guy, go with "D" and you will be glad you did...

Thanks, basically all of the 4-wheeling I do is rock crawling. I do not much enjoy snow bashing or mud flinging...

It's all moot anyway, because another member has a set of wheels/tires that I am going to pick up when driving through their area for my upcoming trip.

 

[Plan d]

D's have a higher capacity and generally a tougher sidewall.

Sponsored