Does airing down an E-rated tire lead to abnormal wear patterns?

[bedhed]

Help me understand this.

As you all are aware, running the recommended 45+ psi in a E rated tire makes for a bone-jarring ride. I've been running MTs for several years now and keeping them at 25psi, but I'm ready to change over to ATs. My question is, when we run an E-rated tire on our Jeeps, does airing down like this lead to abnormal wear patterns? Strictly speaking of highway driving.

I can understand how keeping a tire deflated like this would cause problems when the tire is installed on a larger vehicle, because it's heavier. But, I can't wrap my brain around this being a problem when they are used on a lighter vehicle.

My brain has me seeing it this way:
Lighter vehicle = less sidewall compression.

Less air pressure = mimicked sidewall compression. More of what it would experience with a heavier vehicle.

Thus, deflating to 25-30psi wouldn't have much of an affect on wear patterns.

It's been explained to me, and said to be wrong thinking, but I'm still not grasping it. I keep resorting to the thinking that I just mentioned.

 

[Jerry Bransford]

Exactly where did you hear that 45 psi is recommended? 45 psi is way too high for any tire we'd ever mount onto a Jeep. Also, a Load Range E is way too stiff for our Wrangler TJs anyway, a Load Range C is what's appropriate.

What size tires are you running?

And if you got that 45 psi indication from the tire's sidewall, that only indicates the maximum safe air pressure for the tire. That in no way indicates what pressure the tire should actually be run at. The correct tire pressure varies by the vehicle weight.

 

[Mr. Bills]

Rather than rely upon a knee jerk reaction that "45 lbs is way too high" or "Load Range E is way too stiff," one way to determine the "correct" air pressure for a specific tire size and load rating on a particular vehicle is to weigh your jeep fully loaded and then look up your tire size and load rating on the Rim and Tire Association Load Inflation Table, reprinted here by Toyo Tire:

https://www.toyotires.com/tires-101/tire-load-and-inflation-tables
https://www.toyotires.com/media/2125/application_of_load_inflation_tables_20170203.pdf
It will be relatively easy to extrapolate the tire pressure necessary to support the weight of your jeep. In the case of a 315/75R16-E tire ("metric 35"), at 65 psi it will support its full E load rating of 3860#, at 50 psi it will support 3195# (D), and at 35 psi it will support 2535# (C). [See page 22 of the chart.]

Depending upon the actual weight of your jeep you may find that 24-26 psi is the extrapolated pressure most appropriate for a "metric 35" E load rated tire on your jeep, which not coincidentally is the common wisdom for street pressure for that size tire on a TJ/LJ.

 

[Cornbread]

For what it's worth I have been running my "load range E" coopers for 10k miles at 24psi and they are wearing perfectly.

 

[06lj]

I was running E rated 285/75r16 Duratrac's before downsizing to C rated 265/75r16 Duratrac's. I ran the 285's at 28psi with normal wear. They were as smooth riding as the C rated 265's are now.

 

[bedhed]

Rather than rely upon a knee jerk reaction that "45 lbs is way too high" or "Load Range E is way too stiff," one way to determine the "correct" air pressure for a specific tire size and load rating on a particular vehicle is to weigh your jeep fully loaded and then look up your tire size and load rating on the Rim and Tire Association Load Inflation Table, reprinted here by Toyo Tire:

https://www.toyotires.com/tires-101/tire-load-and-inflation-tables
https://www.toyotires.com/media/2125/application_of_load_inflation_tables_20170203.pdf
It will be relatively easy to extrapolate the tire pressure necessary to support the weight of your jeep. In the case of a 315/75R16-E tire ("metric 35"), at 65 psi it will support its full E load rating of 3860#, at 50 psi it will support 3195# (D), and at 35 psi it will support 2535# (C). [See page 22 of the chart.]

Depending upon the actual weight of your jeep you may find that 24-26 psi is the extrapolated pressure most appropriate for a "metric 35" E load rated tire on your jeep, which not coincidentally is the common wisdom for street pressure for that size tire on a TJ/LJ.

Thanks for the link. I described my thought process, but saying "weight dependant" describes it far better. Being dependant on the specific vehicle is just what I was meaning. I'll jump on they're site and check out the info. It sounds like that will help a lot.

 

[bedhed]

For what it's worth I have been running my "load range E" coopers for 10k miles at 24psi and they are wearing perfectly.

That is helpful. Thanks. I've kept my MTs at 25psi, but I feel like it's hard to know the answer to my question when using MTs to make a determination.

I was running E rated 285/75r16 Duratrac's before downsizing to C rated 265/75r16 Duratrac's. I ran the 285's at 28psi with normal wear. They were as smooth riding as the C rated 265's are now.

Good to know. Thanks!

 

[psrivats]

Rather than rely upon a knee jerk reaction that "45 lbs is way too high" or "Load Range E is way too stiff," one way to determine the "correct" air pressure for a specific tire size and load rating on a particular vehicle is to weigh your jeep fully loaded and then look up your tire size and load rating on the Rim and Tire Association Load Inflation Table, reprinted here by Toyo Tire:

https://www.toyotires.com/tires-101/tire-load-and-inflation-tables
https://www.toyotires.com/media/2125/application_of_load_inflation_tables_20170203.pdf
It will be relatively easy to extrapolate the tire pressure necessary to support the weight of your jeep. In the case of a 315/75R16-E tire ("metric 35"), at 65 psi it will support its full E load rating of 3860#, at 50 psi it will support 3195# (D), and at 35 psi it will support 2535# (C). [See page 22 of the chart.]

Depending upon the actual weight of your jeep you may find that 24-26 psi is the extrapolated pressure most appropriate for a "metric 35" E load rated tire on your jeep, which not coincidentally is the common wisdom for street pressure for that size tire on a TJ/LJ.

Excellent data in that pdf. Thanks for sharing that link.

@Chris you might want to permanently add this on the forum resources section.

 

[JMT]

No, the wear will be fine, but get C rated tires

 

[bedhed]

Excellent data in that pdf. Thanks for sharing that link.

@Chris you might want to permanently add this on the forum resources section.

I agree. Hell, I'm still not finished cyphering through it all. I'm holding up on buying tires until I do fully understand it though. Maybe I've just been an ignorant ass about this for so long, but I had to look up more details about the load index after reading through that info.

I feel like there's some simple math that I wasn't seeing, but can someone explain the reduction ratio part that they mentioned? And wouldn't this apply to our Jeeps, just as it did with the Explorer in their example?