Tire Inflation (LT tires)

[uaintmw]

Please share your comments and experiences regarding the tire pressure your running in load range E (10 Ply) tires on the 5gen T4R's

I have LT285/55/20 Nitto Terra Grapplers (max load 3306, max PSI 80). I'm currently running 50 PSI and noticed the little knobbies haven't worn off the middle of the tire after 500 miles.

I found this calculator on the net. This says I should be running 70 PSI. That seems way too high. What are your thought's on this calculator?

A=B*(C/D)^1.25
A= the tire pressure you want to know
B= the maximum tire pressure,which you can find on the tire
C= The actual weight on the tire, the most discussable item.
D= the maximum load for the tire.

My calulation looks like this:

PSI = 80*(1250/3305)^1.25 = 70.9

1250 is roughly the weight on each tire (T4R curb wt + my wt.)/4 wheels))

Anybody use the chalk method on their E tires yet?

 

[snow&surf]

i'm running:

LT295/55/20 Nitto Trail Grapplers
E Load
3415 lbs @ 80psi max

I called Nitto and asked for their recommended tire pressures on-road, hardpack/rocky off-road, and sand and provided them the gross vehicle weight of my truck. This is what they told me:

On-road = 45psi
Hardpack dirt/rocky off-road going 20-30mph max = 20psi
Sand = 15psi

Seems to be right with the on-road pressure as I don't see any of those knobbies on the tread blocks or lugs with ~1000 miles on them. Your pressures should be close, if not exactly the same as we're almost running the same tire and tire size. Give them a call to find out, drive it a while and see how it wears. If that doesn't work i would suggest the chalk test.

 

[JB.]

....should be running 70 PSI. That seems way too high.

The detailed method is to look up the stock tire in a load/inflation table and, using the door sticker tire pressure, compare the stock tire load capacity to the vehicle weight and note how much tire load reserve Toyota designed in. Then look up the new LT tire in the table and pressurize to get the same OE tire load reserve.

The simple way is to just put 10-15 extra psi in same size LTs which pretty much does the same thing. This would apply the same whether load C, D, or E.

 

[snow&surf]

The detailed method is to look up the stock tire in a load/inflation table and, using the door sticker tire pressure, compare the stock tire load capacity to the vehicle weight and note how much tire load reserve Toyota designed in. Then look up the new LT tire in the table and pressurize to get the same OE tire load reserve.

i tried this method but couldn't find a table for the life of me. i think the problem is my original tires were the dinky and rare 245/60/20 that came on the 5th gen limiteds

 

[SeattleMike]

i tried this method but couldn't find a table for the life of me. i think the problem is my original tires were the dinky and rare 245/60/20 that came on the 5th gen limiteds

As I understand it, the tables aren't published because they are under copyright and generate a source of income for the tire standards organizations. I looked for them as well when I got my "e" tires. The tire dealers do have the load tables and they can tell you the proper PSI. Mine is 44psi. I doubt the OP's is 70psi under a normal load.

 

[JB.]

i tried this method but couldn't find a table for the life of me. i think the problem is my original tires were the dinky and rare 245/60/20 that came on the 5th gen limiteds

Yeah, the simple method gets the win for ease and accuracy, but I should have said, "add 10-15lbs to same size LTs (fixed)". Since your tires are bigger it would be less based on the idea of matching OE tire load reserve. But I wouldn't presume to disagree with Nittos recommendation for pressure. On paper it looks to be a touch on the high side but the LE stock tires have less load reserve (I'm guessing compensated for by an H speed rating) than SR5 or TE and that 45psi recommendation is in line with what I'd expect for the change from P265/70/17.

 

[uaintmw]

Thanks for the replies. Yeah, I couldn't find any load charts either.

45 to 50 is what sounded right. I was just concerned to still see the knobbies on the center tread blocks. I put an email in to Nitto yesterday. I'll post their reply when I get it.

 

[JB.]

....after 500 miles....Anybody use the chalk method on their E tires yet?.....I was just concerned to still see the knobbies on the center tread blocks.

Imo, the more a tire is intended for off-road use, the less reliable something like a chalk test is. 500 miles isn't much. See what they look like at 5K. Fronts and rears are going to wear a little differently as far as shoulder and center which is easily taken care of with rotation. The center vs shoulder vs pressure effect is a subtle one. As long as you're in the general vicinity of proper pressure and the vehicle is aligned, you should be able to forget about tread wear patterns and just focus on handling and comfort preference. If you mostly want more tread life, go a little on the high side for pressure. You could conceivably end up with more center wear this way but I'm betting you'd never see it.

 

[jadatis]

I am the introducer of this formula, and its the one the tire-manufacturers use.
But you calculated wrong , I come to 23,72 psi wich is verry low.
But you often see that at cars for terain,they have often oversised tires.
already am working on a better system. If you keep it at 30 psi you have more savety-factor
made several spreadsheets for it but have now a slow conection on vacation.

Greatings from holland

 

[uaintmw]

You're right. I should have raised the power before multiplying by 80. That still gives me a PSI that is way out of whack.

1250 divided by 3305 = .3782
.3782 to the power 1.25 = .2966
.2966 x 80 = 23.72

My door jamb says 32 PSI. Using JB's easy method, I get 42 - 47 PSI, which is right in line with Nitto's recommendation. Thanks JB

 

[CJ3Flyr]

J.B.'s work/input in this thread is an excellent reference IMHO. Happy to hear numbers being thrown around in the 45psi range:bigok:

 

[CJ3Flyr]

Bump/move

 

[Fuzzylogic]

I have the stock Bridgestones on my SR5 4x4. 32 psi feels too soft. I drive a lot of highway miles. Is bumping the pressured up to 36 lbs. A good idea? The max psi is 40.

I'm also going to be looking for a good highway tire with a slightly more aggressive tread. I had Revos on my Titan. They were ok...but didn't last very long. I don't do very much off road...just some light trailing. I need a nice tire with great highway performance balanced with rain and light all terrain use. suggestions, appreciated.

 

[02SE]

I have the stock Bridgestones on my SR5 4x4. 32 psi feels too soft. I drive a lot of highway miles. Is bumping the pressured up to 36 lbs. A good idea? The max psi is 40.

I'm also going to be looking for a good highway tire with a slightly more aggressive tread. I had Revos on my Titan. They were ok...but didn't last very long. I don't do very much off road...just some light trailing. I need a nice tire with great highway performance balanced with rain and light all terrain use. suggestions, appreciated.

I've had this http://www.toyota-4runner.org/performance-zone-tires-wheels-exhaust-superchargers-more/69101-toyo-265-70-17-open-country-h-ts-installed.html all-season tire for a week. I have been very impressed with the ride, how quiet they are, and how well they do in rain.

In that thread member 'bam-bam' commented how well they do in Snow. Since he and I live in the same area, I trust his opinion that they will do fine.

Here's a review: Toyo Open Country H/T Tire Test | Four Wheeler Magazine Article at Automotive.com

Based on your stated use, they might be a good choice.

 

[jadatis]

You're right. I should have raised the power before multiplying by 80. That still gives me a PSI that is way out of whack.

1250 divided by 3305 = .3782
.3782 to the power 1.25 = .2966
.2966 x 80 = 23.72

My door jamb says 32 PSI. Using JB's easy method, I get 42 - 47 PSI, which is right in line with Nitto's recommendation. Thanks JB

What the car manufacturers used before the "Ford-Firestone-afaire", is the gross axle weight ratings of the car ( GAWR) front and behind mostly diferent.
Mostly back higher then front.
In America they used a power for calculating weight for a sertain pressure of 0.5 for standard load tires and for flatter ones 0.65 . this means for calculating pressure for a sertain load 2.0/1.53 ( european 1,25 for pressure for load = 0,8 for load for sertain pressure.
After 2005 the American equation is upgraded to the European one of 0.8, but you will find many old lists with the old powers.

Now I am at home so I can give you the links to Exel sheet for comparing the diferent powers.
calculateload1.xls - Windows Live
And the next is to an article about a new sugestion of calculation and comparison of this to the power Equation.
tirepressureatreducedloads.pdf - Windows Live
This sugestion states that the indentation of the tire sidewall must stay the same , and I concluded out of it , that the tire-construction bares a sertain part of the load ( in the article about between 21 and 2 % of the maximum load, most modern bigger standard-load tires it will be about 5 to 10 %)
But you can navigate from the 2 links over my complete public map of hotmail for more spreadsheets , some in English where the reference power gets highend up for higher speed then 160km/h / 99m/h.
Translated to the indentation system it would mean the tire may be less indentated for higher speed then the reference speed.

Enaugh for now , first work this out.
The advice pressures can also be for normal car tires, and you have D-load range tires, and then it is the new advice of mostly reference pressure of the original tires of 35psi in America an 36 psi in Europe.
In one spreadsheet about recalculating tire pressure for other then original tires, I have a part for calculating back the weights they used for normal use, in wich you dont have to know the original tires. But in America the normal advice has never be given , and in Europe after about 2000 neither.
Before 2000 it was a by the manufacturer dicided weight for 3 persons and a little load. Nowadays normal advice is for 4 persons and load , an to my conclusion the GAWR are used for it.
you can mail me on hotmail with the same user name as here or give me a PM for more information, for instance a copy of the european equation sheet of the ETRTO.

 

[CJ3Flyr]

I have the stock Bridgestones on my SR5 4x4. 32 psi feels too soft. I drive a lot of highway miles. Is bumping the pressured up to 36 lbs. A good idea? I'd say yes. Try it. Don't go below 32 or above the max pressure listed on the sidewall. I'd guess you'll like it in the 35-37 range.The max psi is 40.

I'm also going to be looking for a good highway tire with a slightly more aggressive tread. I had Revos on my Titan. They were ok...but didn't last very long. I don't do very much off road...just some light trailing. I need a nice tire with great highway performance balanced with rain and light all terrain use. suggestions, appreciated.

I've had this http://www.toyota-4runner.org/performance-zone-tires-wheels-exhaust-superchargers-more/69101-toyo-265-70-17-open-country-h-ts-installed.html all-season tire for a week. I have been very impressed with the ride, how quiet they are, and how well they do in rain.

In that thread member 'bam-bam' commented how well they do in Snow. Since he and I live in the same area, I trust his opinion that they will do fine.

Here's a review: Toyo Open Country H/T Tire Test | Four Wheeler Magazine Article at Automotive.com

Based on your stated use, they might be a good choice.

:iagree:


Jadatis, nice post! The .pdf link is great...:cheers:

 

[doramider7]

I am the introducer of this formula, and its the one the tire-manufacturers use.
But you calculated wrong , I come to 23,72 psi wich is verry low.
But you often see that at cars for terain,they have often oversised tires.
already am working on a better system. If you keep it at 30 psi you have more savety-factor
made several spreadsheets for it but have now a slow conection on vacation.

Greatings from holland

You're right. I should have raised the power before multiplying by 80. That still gives me a PSI that is way out of whack.

1250 divided by 3305 = .3782
.3782 to the power 1.25 = .2966
.2966 x 80 = 23.72

My door jamb says 32 PSI. Using JB's easy method, I get 42 - 47 PSI, which is right in line with Nitto's recommendation. Thanks JB