LT Tire Pressure
- Thread starter Muddy Duck
- Start date
Misterquad
New member
Actually, this whole topic became a game of telephone.
jrandom
New member
Ahem, duh all this is moot... the answer is "42"
https://www.youtube.com/watch?v=aboZctrHfK8
:moony:
https://www.youtube.com/watch?v=aboZctrHfK8
:moony:
Misterquad
New member
Hey Greg look, we agreed on liking the same thing. Well, that is a start.
JB.
New member
"Extending the line for LT down past where it ends (because load tables stop there) in this chart might seem to imply that making a pressure adjustment when switching to LT isn't important since it appears there would still be load reserve at 32psi even if no additional pressure was added, but that doesn't mean there's no benefit to adding more pressure (leaving it at 32 would be the equivalent of around 20psi in the stock tire). For one thing, the curve bends more as it goes down the chart towards zero psi, so calculating it as a straight line overestimates load capacity. Secondly, having plenty of load reserve is desirable since tires change over time -- and they don't get stronger.Lower pressures result in more heat which speeds the process. The cumulative effects of dynamic loading, speed, heat, age, hard use -- not to mention the inevitably lower speed rating in an LT -- are all good reasons the load reserve established by the factory tire at recommended pressure should be given due consideration. If nothing else, the level where the tpms triggers should be a good clue to that. Most of this is covered in the doc already linked. There is also the option to Ask a tire engineer. The horizontal lines on the P-metric tires represent the ability to add pressure for special conditions (like high speed) but the extra psi assigns no additional load capacity. The language in load tables indicates that extra pressure for LTs at high speed is recommended, as well, and at lower speed thresholds than P-metric. The capability of a tire in both load and speed necessarily overlap each other." 
Quoted from:
http://www.toyota-4runner.org/engin...s/110299-lt-tires-need-more-air-pressure.html [MENTION=2798]JB.[/MENTION]
I'm not trying to pick on you or anything, but rather point out with the highlighted areas where your logic is somewhat flawed. While many LT tires have very stiff sidewalls, that does not mean that sidewall flex/bulging is an indication of proper loading.
[MENTION=66389]BlackWorksInc[/MENTION]. Came across this again when trying to figure out what had changed with the @/mention function. Not sure why I never responded. Probably for the same reason I'm having a hard time now. I don't get where the disagreement is but believe me, I'm perfectly happy leaving it that way. Figure it's just a language thing.
In any event, per your suspicion below, you might like to take a look at this if you haven't already.
BlackWorksInc
New member
marshal
New member
I'm having a hard time mathing today. My e rated grabbers are max load capable of 3195lbs at 65psi. I've been running 40psi with good luck lately, but it's a total shot in the dark.
I don't know if this math is right or even applicable.
So 3195 max at 65lbs.
Assume each tire carries a max of 1750lbs at any given time, 3195/1750 = .5477. 65x.5477 = 35.6PSI
So I should be running 35.5psi thereabouts?
I don't know if this math is right or even applicable.
So 3195 max at 65lbs.
Assume each tire carries a max of 1750lbs at any given time, 3195/1750 = .5477. 65x.5477 = 35.6PSI
So I should be running 35.5psi thereabouts?
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Ol'Baditude
New member
40psi seems to be the sweetspot with my E rated cooper STT's. Excellent ride and handling when loaded and gives a good pattern with a chalk test. Been up to 44psi, but doesn't seem to make a noticeable difference in any one category so I keep things at ~40.
In regards to some other comments in this thread, 50-65psi on a 4Runner is just ridiculous.
Bevo
New member
Maybe the math works, but that seems awfully low for an E-rated tire.
Jetboy
New member
I don't think air pressure to weight is a linear relationship. The goal of the pressure for me is to serve two functions for normal driving - support the tire profile such that it does not experience excessive sidewall flex during rolling so the sidewalls don't overheat and vehicle handling is good, and to distribute the load as evenly as possible across the tread area.
So there's other variables that affect this like wheel width or tire size. A larger tire generally can be run at lower pressure. I think it will require a little bit of guess work.
I would probably run somewhere between 35 and 40psi unless I see uneven wear in the middle and then I'd lower the pressure.
JB.
New member
I think that quoted text was in response to another member's counterpoint. I was just quoting you and giving you a mention because you originally posted it and I wanted to give you credit.
Ha, ok I get it.
Even with your 4runner expertise, I don't think you could help with my dim bulb problem because the bulb in question aint in my truck.
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carlomagne
New member
Just clicked on this thread for the first time. I'm on 30 psi on my nitto trail grapplers. Time to click on page 1 and see how far off I am from where I should be.
No idea how you guys run E rated LT's at 45-50 PSI. You must be driving around with about 2 inches of tread width making not making contact with the asphalt, and it must feel like your riding on rocks. I run my C rated BFG2's (stock size) at 35 PSI and that seems about perfect in terms of ride quality and even tread wear. If I run up to 40 PSI+ I start to notice that the edge of the tread shows no contact with the asphalt. I don't care what equations your using that tell you to ride with 46 PSI....if you have the outer 1 inch of tread on either side of the tire not making contact with the asphalt, something is wrong and your equation is definitely not accounting for something. I've had my share of C,D,E tires on Jeeps etc....I've never run any of them near the PSI's mentioned. No issues, and they last the advertised 40-60k depending on the brand.
I'm convinced that 80% of the people here with LT's are running with over inflated tires thinking they have a 2500 pickup. Absolutely no way you guys running at 46PSI are getting full tread contact and your rigs have to be squirly as hell.
I'm convinced that 80% of the people here with LT's are running with over inflated tires thinking they have a 2500 pickup. Absolutely no way you guys running at 46PSI are getting full tread contact and your rigs have to be squirly as hell.
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Ol'Baditude
New member
Hehe... Nice.
scanny
Senior Member
I agree, noticed the same thing. Now, having my C load Duratrac on 35-37 psi for 55,000 miles without any issues, I can say for sure that it's correct pressure for C load on 4Runners.
Jhalko
New member
Are you serious? I'll take their actual math versus all the exaggerated math stats you just made up.
Jeremy556
New member
He is running 35s. Tires with larger diameter and more interior volume take less PSI to carry the same load.
Some examples:
265/70/17: 44psi
285/70/17: 38psi
305/70/17: 33psi
Jeremy556
New member
Search google for "LT Load Inflation Table" you'll come up with the tire industry load/inflation table which will list the PSI required to carry a certain load by tire size.
If you want to support 1750lbs, with 35x12.5/17s, you would need 25psi.
IIRC, the stock 4runner recommended PSI is based on a load of somewhere around 2400 lbs (lots of safety margin), so to match stock load carrying, you would be around 35
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FrontRange4Runner
New member
I have been running 40 psi on my stock size cooper ATP's for nearly 50k. Slightly less harsh then 44, no drop in mpg, and the vehicle handles well. 50+ psi is insane, unless the Runner is loaded wayyy beyond what the stock suspension is rated to handle. With no weight, it would simply be a contest between you and the Runner, to see who rattles apart first.
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