Load Range C vs E
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Joined: Nov 2015
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From: Ontario - GTA
In my experience, the load range does indeed make a difference on ride quality, but it is far from the only factor to consider in regards to tires.
Even in the same load range, there is a lot of variability between brands. A Goodyear Duratrac or MT/R tire is generally significantly more flexible than your average street tire in the same load range.
Air pressure also has a major impact on ride quality. If you run pressures significantly higher than recommended, for the vehicle, the ride will be extra harsh, though you may also lower rolling resistance and tire wear to a degree.
As you go larger on tires you can actually decrease tire pressure to a degree, depending upon the load rating of the tire. As a general rule of thumb, you can interpolate the tire's maximum load capacity as being proportional to maximum tire PSI. So for example, a tire rated for 5000 lbs at 50 psi should be able to support around 2500 lbs at 25 psi. This is only a general rule, and it will vary slightly tire to tire. Tire manufacturers used to publish charts for their tires; only a few still do publicly for liability reasons.
On my TJ I run 315/75R16 Duractrac tires (equivalent to 35x12.5R16), which are E-rated. As long as I keep the tire pressure reasonable, say 26 psi, the ride quality is still decent. In certain off-road scenarios, it's typical for Jeep owners to run 8 psi without beadlocks or 4 psi with beadlocks. (I probably wouldn't also dare to go below 12 psi on a F150 without beadlocks though.) You would not want to run those low pressures at any real speed though. The lower the tire pressure, the higher the risk of blowout.
The sidewall height is also another factor in tire compliance. If you're running massive 22" rims, you have significantly less room for the tire to compress than someone running 15" rims. (That's why most TJ owners stick with 15" rims with 35s.) I'm not quite sure, but I suspect the smallest rim you can run on an F150 is 17".
Even in the same load range, there is a lot of variability between brands. A Goodyear Duratrac or MT/R tire is generally significantly more flexible than your average street tire in the same load range.
Air pressure also has a major impact on ride quality. If you run pressures significantly higher than recommended, for the vehicle, the ride will be extra harsh, though you may also lower rolling resistance and tire wear to a degree.
As you go larger on tires you can actually decrease tire pressure to a degree, depending upon the load rating of the tire. As a general rule of thumb, you can interpolate the tire's maximum load capacity as being proportional to maximum tire PSI. So for example, a tire rated for 5000 lbs at 50 psi should be able to support around 2500 lbs at 25 psi. This is only a general rule, and it will vary slightly tire to tire. Tire manufacturers used to publish charts for their tires; only a few still do publicly for liability reasons.
On my TJ I run 315/75R16 Duractrac tires (equivalent to 35x12.5R16), which are E-rated. As long as I keep the tire pressure reasonable, say 26 psi, the ride quality is still decent. In certain off-road scenarios, it's typical for Jeep owners to run 8 psi without beadlocks or 4 psi with beadlocks. (I probably wouldn't also dare to go below 12 psi on a F150 without beadlocks though.) You would not want to run those low pressures at any real speed though. The lower the tire pressure, the higher the risk of blowout.
The sidewall height is also another factor in tire compliance. If you're running massive 22" rims, you have significantly less room for the tire to compress than someone running 15" rims. (That's why most TJ owners stick with 15" rims with 35s.) I'm not quite sure, but I suspect the smallest rim you can run on an F150 is 17".
You also bring up a good point about wheel size. Agreed, that would probably make more of a difference. I had been planning on 17's, however due to recently hearing that a Gen 2 17" raptor wheel does not fit a 2021 in that it rubs the caliper on the rear, it has me contemplating 18's instead. I've seen 17's on a 2021 before so obviously some wheels do work, but no way to know if the specific wheel I have in mind will work or not without trying first, which could be an expensive experiment!
17's on a 2021 here, similar to what I had originally planned.
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From: Ontario - GTA
You need to look at the sidewall load rating.
EG
BFG KO2 315/70r17 C Rated: 63 lbs has a load rating of 2,535lbs
BFG KO2 315/70r17 E Rated: 62.4 lbs has a load rating of 3,195lbs
Its very important that the load rating exceeds (ok meets or exceeds) the GVWR of the truck and of each axle. Which I don't think will be a problem on the F150 even with "just" a C rated tire. Do your own homework based on your truck to determine the right load rated tire
EG
BFG KO2 315/70r17 C Rated: 63 lbs has a load rating of 2,535lbs
BFG KO2 315/70r17 E Rated: 62.4 lbs has a load rating of 3,195lbs
Its very important that the load rating exceeds (ok meets or exceeds) the GVWR of the truck and of each axle. Which I don't think will be a problem on the F150 even with "just" a C rated tire. Do your own homework based on your truck to determine the right load rated tire
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From: Boston, Ma
The load rating on either would be more than enough for my needs. If the C tire offers a noticeably better ride unloaded, or at least not heavily loaded, then I'd concentrate my search around those. If it really doesn't make much of a difference then it won't be a factor.
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From: Ontario - GTA
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Thread Starter
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Joined: Nov 2015
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From: Ontario - GTA
I don't have a max tow truck, so no issue there. The wheel I am considering is a 17x9 +25. The manufacturer said it will fit, but I don't think they've tried it on a '21 to confirm.
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From: Minneapolis, MN
It's been my experience that higher load range tires, E in this case, last longer.
I am currently at about 70k miles on a set of Load Range E Cooper Discoverer STT tires, for example. Getting close to replacing them in a year or two.
As far as the ride difference, it is noticeable, but it also doesn't bother me.
I am currently at about 70k miles on a set of Load Range E Cooper Discoverer STT tires, for example. Getting close to replacing them in a year or two.
As far as the ride difference, it is noticeable, but it also doesn't bother me.