Swapping Tires: Load Range E to C

Serbonze

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Six years ago I bought my TJ and told the local tire shop that I wanted 33s. They went ahead and put them on and I ended up with Cooper Discoverer STTs on 16” wheels. Because of the size, they happened to be load range E.

From years of Jeep forum participation I became aware that individually, the Bilstein 5100 shocks that I had or the load range E tires were not the best choice for a TJ. In fact, I have been personally questioned, and have seen others questioned, about their choice of using a load range E tire.

A few months ago I swapped out my shocks from Bilstein 5100s to Rocksports. That switch was immediately noticeable and took away much of the small event harshness from everyday driving.

I then decided that maybe it was time to make a tire switch. I had been really hesitant because I knew it was going to be expensive since I would need to buy new tires AND wheels. Last week I pulled the trigger.

I think I may have a unique scenario though, which is why I’m writing this post. I have not been able to find anyone else that swapped the same size, brand, and model of tire from E to C with no other changes to the Jeep.

So the result?

I finished swapping them and my wife and I hopped in and drove around the block. I’ll be honest, it wasn’t the “Holy Shit” come to Jesus moment that I was expecting. The ride difference was very subtle, and we both came up with the same description as it being “smoother”.

I went out today and drove a twenty mile round trip route that I take several times a week and that I know very well. I know certain rough patches of the road that are coming up and how the Jeep reacts to them. After that ride today, I stick with the initial thought of everything being smoother, and still not the “Holy Shit what have I been missing” reaction that I was anticipating.

In summary, the load range C tires are nice. The ride IS better. If I was buying tires for the first time I would suggest buying them. However, if you already have a set of perfectly good load range E tires I don’t think you need to spend the money to swap them until you need new tires, and even then only if you want to try them.

*My opinion, for my Jeep*, is that the shocks made a greater difference in the quality of the ride. However, I reserve the right to amend that opinion as I get more time with these tires. ;)

Because someone will ask, the load range E tires were at 23psi and the Cs are at 26psi.
 
This is my experience as well. Unfortunately with my 35s, they are D range instead of C. But, I was coming from E range, so it actually made a very noticeable difference. If I ever need new tires, the only ones I've found with a load range C in a 35X12.50XR17 size, are the Goodyear Wrangler MT/R Kevlars.

For whatever reason or another, there are hardly any tires in load range C for 16" or 17" wheels.

So, when the time comes, I'll put those on, but for now, my BFG KM2s are load range D, and even that was a very noticeable improvement over the load range E on my former Duratracs.

I was running both at 26 psi, which seems to be the sweet spot for me.
 
. . . I finished swapping [Cooper Discoverer STT load range E to Cooper Discoverer STT load range C] and my wife and I hopped in and drove around the block. I’ll be honest, it wasn’t the “Holy Shit” come to Jesus moment that I was expecting. The ride difference was very subtle, and we both came up with the same description as it being “smoother”.

. . . In summary, the load range C tires are nice. The ride IS better. If I was buying tires for the first time I would suggest buying them. However, if you already have a set of perfectly good load range E tires I don’t think you need to spend the money to swap them until you need new tires, and even then only if you want to try them. . . . My opinion, for my jeep, is that the shocks made a greater difference in the quality of the ride. . . .

I appreciate your observations, which are consistent with my own.

Load range E tires are often vilified in online forums as being unreasonably stiff with a harsh ride, but in reality they are not as bad as characterized at typical street pressures of 26 psi and below. Is the load rating of a "C" tire better matched to the weight of a jeep? Absolutely. Is that any reason to get rid of a perfectly good set of E rated tires? I think not. To the contrary, in some applications the thicker sidewalls of E load rated tires can be an advantage, e.g. areas with sharp volcanic rock and debris from active logging operations.
Everyone's needs are different.
 
@Serbonze, thats for the writeup. What would be cool to see is the difference in the sidewall of the E vs C aired down. This is where the C rated tire will shine off-road vs the E-Rated tires.

I'm on Duratrac E's now, and they ride better than the D Rated Maxxis tires. IF I ever decide to change tire size I'd probably look at C rated 35s, just to be able to try the difference myself.
 
@Serbonze, thats for the writeup. What would be cool to see is the difference in the sidewall of the E vs C aired down. This is where the C rated tire will shine off-road vs the E-Rated tires.

I'm on Duratrac E's now, and they ride better than the D Rated Maxxis tires. IF I ever decide to change tire size I'd probably look at C rated 35s, just to be able to try the difference myself.

I still have the Es in my garage, but honestly have no desire to swap one on the Jeep just to air it down to take a picture. :)
I can tell you that I aired them down to around 14psi before the sidewall showed signs of collapsing.
 
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Bear in mind that the increase in tread footprint when airing down a radial tire will be in the length more so than the width. The difference in sidewall bulge between E load rated and C load rated tires suggesting that the C load rated tire has a more compliant tire carcass is just part of the equation. Also, not all E load rated sidewalls are the same, nor are all C load rated sidewalls. Some have two plies, some have three. The denier of the thread and the material used in those plies will be different as well.

All of this makes it difficult if not impossible to draw rational conclusions as to highway ride comfort and offroad ability from a load rating alone.

What I find most useful are head to head comparisons such as comparing C and E versions of the same tire or "I used X tire for several years on the trails in my area and observed ABC, then switched to Y tire for the the same trails and observed XYZ, and based on my observations ___ tires work better for what I do with my jeep where I do it." Blanket statements such as "C load rated tires are 'better' than E load rated tires in our TJ's" are not particularly useful.
 
Good write up @Serbonze . Like to read different opinions about a tire subject that seem to be bias to one letter. You also point the part that many people not seem to understand abut Jeep ride quality, the Shocks!

I can't spoke about tire quality or construction, Work Confidentiality...

The Load range C tire is the more common recommend for out TJ models due the Load Rating on a single unit. Our Jeeps will rarely carry a big load for extended times so no require bigger Load Rating at the 26 psi we run them.

Are this make it better tire for the TJ's?

Yes and No, all depends the manufacturer. That is why certain load range are not on certain tire size on certain manufacturers.

I do move from 33's Load range C to 35's load range E, difference noted almost none. Just the expected offroad advantage and the tire size.

Really like to discuss at large but I can't, still need a Job that sustain my Jeep addiction.
 
One thing I forgot to include in my original post. There was only a two pound difference between the two tires, with the load range E weighing more.
 
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Thanks for the update. I believe my experience is roughly the same, although I went to a different size and model generation when I bumped UP from C to D. I'm running Bilstein shocks for now. I was running some 32 x 10 BFG Mudterrains KMs. They were stock JK Rubicon takeoffs and are load range C. I didn't care for the look they gave me, so I found some 33 x 12 BFG MudTerrains KM2s in Load Range D. I was running the KM's at 30 PSI and the KM2's at 26.

I noticed an immediate uptick in small event harshness. Large impacts are still about the same, but I swear I can feel tar snakes roll under the tires now. Its crazy.
 
. . . I believe my experience is roughly the same, although I went to a different size and model generation when I bumped UP from C to D. I'm running Bilstein shocks for now . . . .

I noticed an immediate uptick in small event harshness. Large impacts are still about the same, but I swear I can feel tar snakes roll under the tires now. Its crazy.

Look to your Bilstein shocks, not so much the tires. I would be willing to wager that if you used a different shock with your current load range D tires that the "tar snakes" would no longer bother you.