LT tires need more air pressure.

[mo_mo]

So, what pressure should I be running LT265/70R17 BFG TA KO2 on stock 2015 SR5P here in San Diego? :help: :biggrin2:

35?

44?

What did the shop set them at?

Since that tire comes in both C and E Ranges with different load indexes, then somewhere between 34.8 and 52.2
***bad math with no idea what I'm doing below***
Using the Toyota axle weight / 2 method:
C Range (Load Index 112) = 34.8
E Range (Load Index 116) = 43.1

Using the Toyota stock P load scaling method:
C range = 42.2
E Range = 52.2

Let us know what you find works best for you.


FYI: I'm getting LT265/70R17 C Range Load Index 112 Duratracs installed and plan on running 42 psi to start. I might drop them down and then crank them back up depending upon how they break-in.

 

[2GOFAST]

thanks for the info

 

[freeflight]

Nice work, tagged

 

[jicko]

So, what pressure should I be running LT265/70R17 BFG TA KO2 on stock 2015 SR5P here in San Diego? :help: :biggrin2:

35?

44?

Discount tires set them at 40psi.

I am currently running 45psi, after starting at 44 (prorated from the pressure of P tires), and going +/-1, +/-2 etc.. testing.... and finding that 45psi runs the best for me.

 

[02SE]

Maybe I missed it while skimming this thread, but I didn't see any mention of the fact that a P-metric rated tire's load carrying capacity, is derated by a factor of 1.10 (approx. 9%) when used in a Van, Pick up, or SUV application. As required by Federal Motor Vehicle Safety Standards.

So when looking at a load inflation table for a P-metric tire, reduce the load carrying capacity of the tire by a factor of 1.10, to arrive at the true load carrying capacity in a Van, Pick up, or SUV application, for a given inflation PSI.

 

[afludgate4r]

get it done

 

[tornado_chase_hike]

This is the most informative discussion I've seen on this topic. I will soon be getting tires for my new 4Runner and now have a much better understanding of the choices. Thanks!

 

[stanleybb50]

Now I'm still very very confused on this topic and keep obsessing about it... When you look at the specs, our OEM tire vs a new C rated Duratrac, the 265-70-17 Duratracs hold more weight at a lower psi... Not sure why I should be running them at 42-47 psi given this information. Seems to me I need to be at a lower psi. Tires don't necessarily carry that amount of plys (ie 6 or 10 for c or e) technically, but more about total weight handling.

I just got these last week and tried 42 and felt like I was allll over the road. Then I tried 38, 35, and now down to 30 and it feels perfect at 30 which also corresponds with the math for Duratracs based on the weight of my 4th Gen.

Trust me I'm not saying I'm right because I'm nobody and frankly ignorant on this stuff. I'm just trying to get the best wear and keep my family safe. And it feels safest at 30 psi, because I felt all over the road at higher pressures. Also felt cold to the touch after a 30 min drive last night - so doesn't seem to be creating excess heat either.

Gonna post a couple screen shots and pics here. One of my alignment (which is arguably out on caster because I have a frozen LCA bolt they couldn't break) and then two of the specs between what I think is the OEM tire vs the Duratracs.

Thanks for any thoughts and/or replies!

*I was driving on Toyo Open Country AT2's in P 265/70/17 with 30 psi for the last 3 years with the old alignment and everything felt great (for the record. So it's likely not the alignment causing the all over the road feeling - especially since it t feels perfect with the Duratracs at 30 psi).

 

[JB.]

Now I'm still very very confused on this topic and keep obsessing about it... When you look at the specs, our OEM tire vs a new C rated Duratrac, the 265-70-17 Duratracs hold more weight at a lower psi...

The basic message of this thread is that an LT tire of the same dimensions and psi as a Standard Load tire, will carry less load (About 15 to 20% less in an SUV application).

That's it.

Afterward, determining "proper" pressure is all about whichever reference point you choose. You can reference the load inflation tables. You can reference the load reserve of the stock tire at door sticker pressure, just to name two.

Your tire stat examples don't work because they reference max pressure which is distorted in the case of the Standard Load tire because the increases in load capacity that come with additional pressure cease at 35psi even if the tire is inflated higher to its maximum (51lbs). Ignoring the size difference, in effect, the pics compare 35psi to 50psi.

At 30psi in your Duratracs, you still have about 13% load reserve at GVW. Hopefully, that makes you more comfortable. On the other hand, the stock tire has 37% GVW load reserve at the recommended 32psi and a survey of various vehicles and their stock tire fitments reveals that seldom does the GVW load reserve go below 20%. You can decide if that means anything. And then there's speed rating.

It's up to you how you weigh the various factors and which reference point(s) you choose.

 

[stanleybb50]

The basic message of this thread is that an LT tire of the same dimensions and psi as a Standard Load tire, will carry less load (About 15 to 20% less in an SUV application).

That's it.

Afterward, determining "proper" pressure is all about whichever reference point you choose. You can reference the load inflation tables. You can reference the load reserve of the stock tire at door sticker pressure, just to name two.

Your tire stat examples don't work because they reference max pressure which is distorted in the case of the Standard Load tire because the increases in load capacity that come with additional pressure cease at 35psi even if the tire is inflated higher to its maximum (51lbs). Ignoring the size difference, in effect, the pics compare 35psi to 50psi.

At 30psi in your Duratracs, you still have about 13% load reserve at GVW. Hopefully, that makes you more comfortable. On the other hand, the stock tire has 37% GVW load reserve at the recommended 32psi and a survey of various vehicles and their stock tire fitments reveals that seldom does the GVW load reserve go below 20%. You can decide if that means anything. And then there's speed rating.

It's up to you how you weigh the various factors and which reference point(s) you choose.

Great post! This helps a lot. Thank you.

Either way I'll definitely try to heed your advice and bump it up for more reserve. Hopefully I can find a happy point where I don't get the wandering on the road.

Thanks again - very helpful.

 

[stanleybb50]

For the record, I settled in around 38 psi for the 265-70-17 Duratracs. I think the initial "squirrely-ness" was likely the mold release or something.

Feels pretty good around 38 psi as a happy medium. At 30 and then like 34, it felt and sounded a bit like the tires were flexing a bit too much around bends.

Thanks again for the advice.

 

[D Farms]

the sweet spot for my 315/75r16 ko2s is about 26 psi for my truck, offroad I like them around 10-12. the reality is that the only advantage of inflating my tires to a higher pressure is higher bead retention. my tires have a max load of something like 3750 at 65 psi. my truck weighs 4500lb.

here is my logic

the 265/70r16 will have a smaller foot print than the 315/75r16 so in order to get the same "tire compression spring rate feel" you lower the pressure. you also have to consider the tire is taller so it will sway more, but if its wider also then it will be more stable, sort of canceling each other out.

one disadvantage of a big tire is more mass, so the unsprung weight increases. so your suspesension cant push the tire around as quickly so the ride is not as good. how do you solve this? lower the pressure and you get this sprung weight effect. if the tire has more give and can compress more the extra weight of the tire and suspension become sprung weight giving you a smoother ride. the give of the tire allows the contact patch to compress and expand just like the suspension. the reality of suspension is that there are multiple levels of sprung weight, the tire tread in contact with the ground is the first level, the spring is the tire pressure, then the next spring is the actual suspension, then the frame which flexes a bit, then the body mounts, then your seat cushion. all of these things affect the ride that you experience. now with all of that being said, the higher the spring rate the more responsive the suspension will be. increase the tire pressure, stiffen the springs and dampers, make it a unibody, sit on the floor of the truck.

logical rant over...

 

[pjbrownva]

So I'm confused...

If I have a choice of the same tire in either P size or LT size.

If I set each tire to their optimum pressure (however we choose to define that term), is the P tire likely to handle better and provide a softer ride than the LT tire?

Or is the answer that their is no difference in ride quality and sound, provided that I inflate the tire to it's proper pressure (which will be higher for an LT rated tire than for a "P" rated tire.

TIA.

-Phil

 

[nomadcat]

emailed Goodyear

My experience is as follows. While I ran LTs on my Wagoneer for years at a higher than sticker PSI, those numbers have been lost to memory.

I bought an 05 Tacoma new and put on Michelin LTX AT2s, E Range version, LTs, but I believe they were 16" wheels. Again, memory fails. I ran them, though at 40 all around. I know that much, and they were fine at 40.

With my 2015 4R Trail, I immediately bought Duratrac LT265 70 17 tires in the E range. I have these exact same tires, size, etc. on my 9000 pound Quadvan and run them at 70, which is perfect.

The tire shop put them at 32 and I didn't notice immediately, but I did notice sloppy cornering and a really soft ride. I then consulted the Internet, where I found all kinds of opinions, knowledge, hearsay, and just plain odd information.

I resolved to bump them up to 40, then quickly put them up to 44. I then emailed Goodyear, who didn't write back immediately, so I called them. I had to explain a few times to the woman the situation - after she initially said "run what's on the sticker." - and she then went and consulted her "tire pressure book" and said to run them "between 55 and 60 PSI." This seems a bit high to me and I have been pondering.

Yesterday, I simultaneously found this thread and got a response to my initial email from Goodyear. Here is what they sent me, which kind of confirms the best consensus that I have seen here:

"Operating air pressure is determined by the vehicle manufacturer. If you're
using the same size tire that came as original equipment on your vehicle,
the proper air pressure is indicated on the door placard or owners manual
of your vehicle.

The air pressure indicated on the sidewall of each tire is the inflation
pressure required to carry the maximum allowable load for that tire.

Vehicle manufacturers have invested considerable time and testing to
establish an air pressure that will provide a smooth comfortable ride in
addition to an even treadwear pattern.

Your OE tires at 32psi carry 2,425lbs per tire. Your LT size tires need to
be set at 50psi to carry 2,470lbs.

Thank you for your inquiry through our web site.

Jennifer - Consumer Relations"


Soooo... based on this, I may bump them up to 50 for a few days and see how that feels. Otherwise, I'm perfectly fine letting them sit at 44.

 

[JB.]

The tire shop put them at 32 and I didn't notice immediately, but I did notice sloppy cornering and a really soft ride..

I then emailed Goodyear, who didn't write back immediately, so I called them. I had to explain a few times to the woman the situation - after she initially said "run what's on the sticker." - and she then went and consulted her "tire pressure book" and said to run them "between 55 and 60 PSI." This seems a bit high to me and I have been pondering.

Your OE tires at 32psi carry 2,425lbs per tire. Your LT size tires need to
be set at 50psi to carry 2,470lbs.

Thank you for your inquiry through our web site.

Jennifer - Consumer Relations"

It's hard to consistently dot all the I's and cross all the T's. She didn't use the de-rated load capacity for the stock tire. Doing so is how the calculation goes from 50psi to 44.

 

[nomadcat]

It's hard to consistently dot all the I's and cross all the T's. She didn't use the de-rated pressure for the stock tire. That's how the calculation goes from 50psi to 44.

Thanks for that. I'm going to leave them at 44, where they seem to feel good, anyway.

 

[JohnTheLuck]

Great thread which tells me I know nothing about tires !!!

I would like to hear about airing down on trails. I read many times some people telling they lower to about 20 pounds on trails, and back to normal when back on roads. For a 5th gen with LT275/70R17E KO2, 20 pounds seems a bit low if normally used at 44.

 

[TrkyMfns]

FWIW, My 265/70/17 C K02's said 40PSI on the Discount Tire paperwork. They seem fine there, but I will try 42 as well. This is on a stock 2011.

 

[MoonStorm]

Now I'm still very very confused on this topic and keep obsessing about it... When you look at the specs, our OEM tire vs a new C rated Duratrac, the 265-70-17 Duratracs hold more weight at a lower psi... Not sure why I should be running them at 42-47 psi given this information. Seems to me I need to be at a lower psi. Tires don't necessarily carry that amount of plys (ie 6 or 10 for c or e) technically, but more about total weight handling.

I just got these last week and tried 42 and felt like I was allll over the road. Then I tried 38, 35, and now down to 30 and it feels perfect at 30 which also corresponds with the math for Duratracs based on the weight of my 4th Gen.

Trust me I'm not saying I'm right because I'm nobody and frankly ignorant on this stuff. I'm just trying to get the best wear and keep my family safe. And it feels safest at 30 psi, because I felt all over the road at higher pressures. Also felt cold to the touch after a 30 min drive last night - so doesn't seem to be creating excess heat either.

THANK YOU for bringing this particular tire up for debate. Will all the respect for JB and the effort he put into the research, this topic still remains a mystery. Here's why.

I too am having a hard time finding the sweet spot for these tires. Started at 38PSI and they felt horrible. Kept going down and I was still not satisfied. The rear was having a party dancing all over the place. The party actually ended with the aftermarket suspension I just installed. However, I still can't explain the following pictures I took after washing the truck and driving for a couple of miles.

32 PSI rear tire
outer view
inner view

You can clearly see that even at stock pressure, the rear tires don't fully make contact with the ground. There's at least half an inch of unused rubber on each side, which hurts traction and stability.

34 PSI front tire
outer view
inner view
inner view

The front tires look better in terms of usage, due to the front weight bias.

 

[MoonStorm]

So no one cares to venture a guess as to why those pics of the rear tires look so bad at stock pressure? We've given up on the topic?