E rated tire with max psi of 65?

[BurbMan]

I have Nitto Ridge Grapplers that came on the truck when I bought it used, size LT325/65R18 E 127/124Q.

Every E-rated tire I've ever seen is rated to carry its max load at 80psi, so the first trip out with the camper I didn't even look at the tire, I just aired up to 80. Back home 1000 miles later and I see on the sidewall that the max rating for the tire is 65psi.

Sure enough, the Nitto site says may rating is 3860 lbs@ 65 psi. Anybody ever hear of an E rated tire running at 65 psi max?

These are way oversized for the truck (spec calls for minimum 9" rim width, mine are 8"), but after running them on the highway at 80 psi, then on the beach at 20 psi, and at 55 psi unloaded, the truck handles great and wet weather traction/stopping is at least as good as the Revo 3's I had on the Burb.

I was looking for a reason to get rid of these but haven't found one yet....these are about 50% worn, and next set will be the same maybe a size smaller.

[Grit_dog]

And we’ve all had experiences we learned from.
I learned about the right width rims for tires and right pressure for treadwear at the same time, same truck, 1 set of tires.
Put a nice set of 33-12.50 mudders on some 17x8 rims. Bit narrow but not bad. Then moved to Phoenix and kept them aired up more than needed, for mileage (good roads, smooth), minimize scrub on the super hot pavement etc.
thought they were the worst tires ever. Wore out in maybe 25k miles of kid carrying duties. Just the center of the treads.
Getting new tires, and commented how bad the Mickey Thompson s were and tire guy asked what pressures. I told him and he pointed out the error in my ways.

[Grit_dog]

MFL wrote:
We are all knowledgeable, but does not mean correct every time! If you read Burb's link, it has some good info, concerning his tires, tread, etc. It does show a little more on road capable, than off.

Do you truly know Capri, or just read of his own drum beating? Hope no relationship involved!:) Roger Marble was more knowledgeable, and also had more RV type experience. Too bad, he was banned here!

Grit...just curious...why does it often take a day or more, for your posts to show up? Your post above, did not take that long, but was blank for a while? BTW...you are a knowledgeable gear head, and like me, a person who has over used trucks, and tires, while I don't recommend either.

Jerry

Idk why my posts show up late to the party. Haven’t really noticed. But one above may have been in quarantine by the mod! Lol
I don’t know Capri, but everything he’s posted that I’ve read appears to be truth and in depth knowledge.
But this is the internet. I could be more FOS than the next guy. Opinions are worth exactly what they’re worth. Although I’ve learned a lot from the “right” opinions and a fief amount from the “wrong” ones too!

Cheers MFL! And the rest of ya too...

[KMLsquared]

I have general tires Grabber AT on my truck in a 315/75-16 and they are an "E" rated tire at 65 PSI. I too was concerned but trusted their engineers and they have been fine. IF I still had a truck camper I would not have gotten them but the Fifth-wheel tows fine with them.

[BurbMan]

Well I'm feeling pretty lucky right now...on out 1000 mile road trip to PA in October (maiden voyage with the newly-rebuilt camper), I had the rears aired to 80 and was seeing the TPMS tell me 85/86 going down the road at 70 mph. I'm thankful they didn't blow running that much over max.

The flip side is that I'm sure the extra air helped with stiffness and stability...so maybe they would squirm more aired to only 65?

Here is the specs page from the Nitto site for their Ridge Grappler tires.

I've added some notes:

A- This is the size that Ram puts on the truck as OEM. My truck has 18x8 rims.
B- This is the size that's on the truck now.
C- This seems like a good choice for a replacement when these wear out.



This is what Ridge Grappler looks like:

[MFL]

Good to see where your info comes from. While there are many types of tires, if you would have taken the time to read the link Burb posted, it is a hybrid type (dual purpose) tire, that by design, would work best, considering sidewall and tread at 65 psi. Other tires purpose will vary, and while e-rated, may also be less than 80 psi.

As to reading comprehension...I specifically mentioned your buddy Grit, having an issue with his posts. His post will show in the count, and at what time, but the context, and author may not be there for a day or more. It may be a phone related issue, or that a civil engineer is not a technical engineer.

In any case, whether reading posts, links, or from a book, comprehension is key!

Jerry

[CapriRacer]

There seems to be some question about where I got my information that larger sized E Load Range tires use 65 psi max pressure rather than the usual 80 psi max - and that maybe onroad/offroad has something to do with it.

I have in front of me the 2020 Tire and Rim Association (TRA) Yearbook. TRA is the source standard for the load tables (among other things!) for US based tire manufacturers. In that book are ALL the current load tables for EVERY type of tire (except aircraft - separate book - and anything non-standard)

It shows many E Load Range LT tire sizes as having 65 psi max pressures as well as the ones we normally deal with (including sizes that aren't produced!) The tables do NOT refer to onroad/offroad as one of the parameters in determining the max pressure. However, it does reference changes in load carrying capacity for various speeds. (again, no change in the max pressure!)

And lastly, why do my posts take so long to show up? I normally post in the morning - part of my daily ritual. I only recently updated to a smart phone and haven't yet figured out how to connect it to my email alerts. Plus, does this site give email alerts? More things to learn about! (edit: When I clicked to post the above, I found how to get email alerts! Now to learn how to link the phone to my email so I get alerts!)

[MFL]

We are all knowledgeable, but does not mean correct every time! If you read Burb's link, it has some good info, concerning his tires, tread, etc. It does show a little more on road capable, than off.

Do you truly know Capri, or just read of his own drum beating? Hope no relationship involved!:) Roger Marble was more knowledgeable, and also had more RV type experience. Too bad, he was banned here!

Grit...just curious...why does it often take a day or more, for your posts to show up? Your post above, did not take that long, but was blank for a while? BTW...you are a knowledgeable gear head, and like me, a person who has over used trucks, and tires, while I don't recommend either.

Jerry

[Grit_dog]

MFL wrote:

CapriRacer wrote:

MFL wrote:
Where are all the tire engineers when you need them? My wag is that these tires are designed as onroad/offroad, so even though e-rated, a lesser max pressure is best for the hybrid use, that the tread and sidewalls are designed for.

JMO, but I'd not use a wider tire, than what the rim is designed for.

Jerry

So here I am.

It's a long story why some E Load Range tires have a max pressure of 65 psi, but it deals with the burst pressure - ergo larger sized tires will have the lower pressure. It has nothing to do with onroad/offroad.

This is not unique to E Load range tires.

And just to assure some folks: The burst pressure of a tire is many times the max pressure. Tires do NOT burst based solely on the pressure. They will burst if they hit an object hard enough, regardless of the actual pressure in the tire. They'll also burst if cut deep enough to cut cords!

One of our hundreds of tire engineers showed up! Thanks for chiming in. While you SAY burst pressure the reason, then add that burst is many times the max pressure, it would seem that 80 psi rather than 65 psi, would not cause burst.

I disagree with the off/road design, as provided in OPs link, not being a factor. In my experience with off/road motorcycles and the oem tires, they are designed to use lower pressure.

Not sure if CapriRacer has off/road experience, or schooled knowledge of this particular tire, or just making a wag of his own?

Google, our modern day TE may have best answer, for anyone wanting to search! 😉

Jerry

No, Capri is knowledgeable and correct.
And real world, Burbs tires aired up a bit over max, while not the healthiest for tread wear maybe, likely handled better than at 65psi.
I’m no tire engineer, just a dumb gear head civil engineer who has been thrashing light duty trucks for a lot of years in construction. And as part of that, when I have a new 1/2 ton with piddly P or XL tires and am hauling heavy trailers, I’ll air up the 44 or 50 psi rear tires about 10 psi or so over max and enjoy the better handling aspects of a stiffer tire with the load.

That said, I do understand buddy pressure anecdotally and realize that there’s an increased chance of a blowout from a road hazard.

[Grit_dog]

^Agree, from a functional standpoint.

However the real lesson in this thread is all the nay sayers that bemoan those “hooligans” with their big loud ill proportioned tires and how they “must” be horrible for doing truck stuff like towing and hauling big loads and are a danger to themselves and society....... can now pipe down.

We now have a real world review from a real person hauling a real camper who isn’t beating his chest about how cool his brodozer is, but rather now realizes that big tires aren’t the horrific doom n gloom that is generally portrayed here!
(And to top it off, they’re on too narrow of rims, and still do just fine!)

These are things that some of us already know and others refuse to believe.

[garyp4951]

The Nitto 295/70/18 rated 4080# would seem to be a better choice for a truck camper, and would fit your wheels.

[MFL]

CapriRacer wrote:

MFL wrote:
Where are all the tire engineers when you need them? My wag is that these tires are designed as onroad/offroad, so even though e-rated, a lesser max pressure is best for the hybrid use, that the tread and sidewalls are designed for.

JMO, but I'd not use a wider tire, than what the rim is designed for.

Jerry

So here I am.

It's a long story why some E Load Range tires have a max pressure of 65 psi, but it deals with the burst pressure - ergo larger sized tires will have the lower pressure. It has nothing to do with onroad/offroad.

This is not unique to E Load range tires.

And just to assure some folks: The burst pressure of a tire is many times the max pressure. Tires do NOT burst based solely on the pressure. They will burst if they hit an object hard enough, regardless of the actual pressure in the tire. They'll also burst if cut deep enough to cut cords!

One of our hundreds of tire engineers showed up! Thanks for chiming in. While you SAY burst pressure the reason, then add that burst is many times the max pressure, it would seem that 80 psi rather than 65 psi, would not cause burst.

I disagree with the off/road design, as provided in OPs link, not being a factor. In my experience with off/road motorcycles and the oem tires, they are designed to use lower pressure.

Not sure if CapriRacer has off/road experience, or schooled knowledge of this particular tire, or just making a wag of his own?

Google, our modern day TE may have best answer, for anyone wanting to search! 😉

Jerry

[BurbMan]

I thought there was some kind of standard that said D rated aired to 65 and E rated aired to 80, just because I've never seen any deviations from that, but it just goes to show that you don't know what you don't know....I'm always learning new stuff here on the forum and I appreciate the comments and expert opinions.

Buying a used truck is always a compromise...I was willing to accept the 1.5" coil spring spacers ("leveling kit") and oversized tires to get a truck with no rust, documented dealer service over 5 years from a single owner, no accidents, no evidence of aftermarket tuning, and overall really clean.

I was expecting to be hugely disappointed with these tires in terms of traction (contact patch too large), noise, vibration, and squirm under load. To my surprise the truck is quiet and smooth as glass at 70 mph, very stable with 3100 lbs of camper in the bed, and very sure-footed on wet roads. Snow performance is TBD...

There is evidence of rubbing on the front trailing arms at max steering angle (full lock) but no wear or damage to the inside sidewalls.

The rims are OEM and in great shape, no scratches or pitting at all. I haven't decided whether to get wider rims or narrower tires, but I probably have another year to figure it out.

The leveling kit makes the truck look badazz when empty, but it sags a little in the rear when loaded with the camper. I can't lose the leveling kit without first going to smaller tires, and my alternative is adding air bags in the rear if I stay with this size and go with bigger rims with the proper offset to avoid rubbing.

My main concern was running fully loaded at only 65psi, but sounds like I'll be OK for now.

[CapriRacer]

MFL wrote:
Where are all the tire engineers when you need them? My wag is that these tires are designed as onroad/offroad, so even though e-rated, a lesser max pressure is best for the hybrid use, that the tread and sidewalls are designed for.

JMO, but I'd not use a wider tire, than what the rim is designed for.

Jerry

So here I am.

It's a long story why some E Load Range tires have a max pressure of 65 psi, but it deals with the burst pressure - ergo larger sized tires will have the lower pressure. It has nothing to do with onroad/offroad.

This is not unique to E Load range tires.

And just to assure some folks: The burst pressure of a tire is many times the max pressure. Tires do NOT burst based solely on the pressure. They will burst if they hit an object hard enough, regardless of the actual pressure in the tire. They'll also burst if cut deep enough to cut cords!

[Grit_dog]

Well Burb, you’ve seemed to defy the “logic” of the rvnet patriarchs, lol!
Yes the big tires are generally max rated at 65psi. Not to worry. More air volume and particularly more width, holds more weight at the same pressure as a smaller tire.

To maximize tire life though, especially with the narrow rims ballooning the tread a bit, make sure you’re running the lowest safe pressure that you can stand handling wise, when empty.
The Ram we just got sits on 37s and the (very expensive) tires don’t have many miles on them, but the PO ran the pressure too high for the load. He was running 65F/60R And even though the tires are on 12” wide rims and should run as flat as they possibly can, the centers of the treads were wore down 3 to 4 32nds rear and 2/32 front while the edges of the tread is still virtually new.
I’ve got them aired down to a little under 50F and 35R to even out the treadwear.
Tired a bit lower but it drove a bit mushy.

[edbehnke]

yes, E rated tires do have different psi ratings.