# Recommended vs. Max Tire Pressure



## protege26 (Jul 26, 2006)

Ok. I am confused. I have a 2006 SE 4x4 with the factory BF Goodrich Radial Long Trail T/As on her.

We have had many cold mornings and days here lately so the wonderful Tire Pressure Monitoring System has been lighting up. So that leads me to a few questions. I've searched but to no avail.

The recommended pressure on the door is 35 psi. But that is also the max pressure on the tire itself. I have never heard of a manufacturer having the recommended pressure be the max. That makes me feel a bit uncomfortable driving around with the max (more when the tires are hot) all the time. What are everyone's thoughts on this?

Also, how low do the tires need to get before the TPMS light kicks on? During the summer I had my tires at 34 psi cold and now the light comes on at around 31 as I can figure. Is this about right? 

Just curious.

K.R.


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## Z_Rated (Apr 29, 2006)

When I first got my truck it would go off at around 28psi with average low temps in the 40's (which is low and about normal for my TPMS to activate). Last week up on the Rim around 6500 feet it went off at about 33psi below 32 degrees F (which is close to where I run my pressures normally). I think there are some bugs in the system when in the cold. I say this because of my own experiences and all of the people who have had problems with the TPMS as well. Most of whom I believe experienced it in the cooler/colder months/climates.

I do not have the same tires so I do not know about your max pressures and I believe mine have a higher max. Check your manual and check it against your door sticker (tire size as well) and tire sidewall. Seems odd to me as well to be running at the max. Let us know what you find and I'll double check mine too. Z


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## Z_Rated (Apr 29, 2006)

BFG Long Trails max 44psi, sticker recommends 35psi. TPMS supposed to activate about 28psi around 20mph. When I was on the Rim the TPMS was active below 10mph within 1/16 mile and the temperature was in the high 30's with all tires reading 32psi or more. Definitely not working as defined by the manual, first issue with it since new. No more issues since leaving the high country.

Might consider comparing with a second tire gauge? Digital being ideal. Z


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## protege26 (Jul 26, 2006)

Well, the owners manual doesn't say anything about specific pressure, just to go by what is on the door decal, which is 35 psi. The tire wall says max psi of 35, and those are the specs listed for that size on Tire Rack as well. I have the 265/70 16. For the 17" tires, 44 is the max. Is that what you meant? 

I know I'm not the only one here with a SE with stock BFG tires. Has no one else wondered about this? I'm just nervous riding around with the max pressure all day long. I may have to call BFG and see what they say about it. 

The manual did say that the cold weather would make the TPMS activate the light, which makes sense due to the pressure going down in cold weather. But it didn't say specific when it cuts on. But from my experience, when I had the tires at 34 psi all summer, then the first cold morning and the light kicked on, all the tires were at 31 psi. So I am guessing that at around 3 pounds it kicks on. But if that is the case, it should kick off once the tires get hot, because they easily gain 3 pounds once they get hot. 

Hmmm. I'll have to do some more checking I guess.

Thanks so far!
K.R.


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## Z_Rated (Apr 29, 2006)

If you are at 35psi then you are not at the max so you should be fine. My tires are stock BFGs also, but I have a different model 4x4. Once I got off of the mountain, about 16 miles at 65+mph, stopped to refuel and restarted the truck the light was off. Difference of about 2500 feet and 30 to 40 degrees F. I did not need to air up and haven't since. At last check I'm at 35psi for three tires and one at 34psi. According to my gauges I did not lose any pressure, the TPMS just went off and prematurely to boot. Temps or elevation?

Try to figure out how much you lose overnight and air up the difference (35psi + the difference), then compare that to what BFG tells you would be safe to drive on if you call them. Granted, I'm thinking about 38psi (3psi loss) should be acceptable, but not more 39psi for a 44psi max tire. I'm no expert, just making a suggestion. Good Luck, Z


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## jerryp58 (Jan 6, 2005)

protege26 said:


> Well, the owners manual doesn't say anything about specific pressure, just to go by what is on the door decal, which is 35 psi. The tire wall says max psi of 35, and those are the specs listed for that size on Tire Rack as well.
> 
> Thanks so far!
> K.R.


The MAX load rating will also affect MAX tire pressure; so you can have the same size and model tire, but the MAX pressures could be different. At least that's what I believe I saw when I was shopping for my Kuhmos -- the Road Venture HT came in either SL (standard load rated for MAX 35 PSI) or XL (extra load rated for MAX 44 PSI). Anyway, I'd stick with the side wall spec. It's surprising that the tire placard PSI and the sidewall MAX PSI for stock tires would be the same. I don't like inflating to MAX, but I ran my 44 PSI tires at 40-42 and I run my 35 PSI tires at 32-33 because I'm pretty sure if you run too low a PSI, the tire (and the air in the tire) will heat up because the sidewall is flexing more while the tire turns. If you call BFG, you may want to ask them what kind of PSI increase you can expect as the tire heats up.


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## protege26 (Jul 26, 2006)

jerryp58 said:


> It's surprising that the tire placard PSI and the sidewall MAX PSI for stock tires would be the same. I don't like inflating to MAX, but I ran my 44 PSI tires at 40-42 and I run my 35 PSI tires at 32-33 because I'm pretty sure if you run too low a PSI, the tire (and the air in the tire) will heat up because the sidewall is flexing more while the tire turns. If you call BFG, you may want to ask them what kind of PSI increase you can expect as the tire heats up.


Yeah, that is my thought exactly. BFG's website says the same thing. I have a passenger tire with the max PSI being 35. And like you said, it is weird that the recommended pressure on the door from the manufacturer is that PSI as well. 

I like you, am unsure of inflating to the max on the sidewall of the tire. That is why I kept it at 34 or so. But this makes the TPMS kick on every morning when it is cold. I do think I will do the test at night and then test in the morning to see what the drop in pressure is. However I still will try and give BFG a call tomorrow and see what they say and I will ask how much the pressure increases as the tires heat up. I am sure it goes up at least 3 lbs, and if that is so, I am not happy at all driving down the interstate 75 miles an hour with 3 PSI above the max in my tires. LOL. 

I'll let you all know what I find out tomorrow evening. Anyone else want to chime in? Have at it!!

Thanks!
K.R.


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## jerryp58 (Jan 6, 2005)

protege26 said:


> Yeah, that is my thought exactly. BFG's website says the same thing. I have a passenger tire with the max PSI being 35. And like you said, it is weird that the recommended pressure on the door from the manufacturer is that PSI as well.
> 
> I like you, am unsure of inflating to the max on the sidewall of the tire. That is why I kept it at 34 or so. But this makes the TPMS kick on every morning when it is cold. I do think I will do the test at night and then test in the morning to see what the drop in pressure is. However I still will try and give BFG a call tomorrow and see what they say and I will ask how much the pressure increases as the tires heat up. I am sure it goes up at least 3 lbs, and if that is so, I am not happy at all driving down the interstate 75 miles an hour with 3 PSI above the max in my tires. LOL.
> 
> ...


Has anyone ever asked a dealership if the PSI threshold can be reprogrammed?


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## Z_Rated (Apr 29, 2006)

That's a good question... let me ask L0L


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## Z_Rated (Apr 29, 2006)

Well now, first dealership says 33psi will set it off (with which I disagree for mine) second says below 29psi (which is in line with my manual) AND also 41psi on the high side as well, which I was unaware of. Interesting, something to try out for sheer curiosity. As for Winter both say to run 36psi, Summer being 32psi. Anyways, both say the TPMS can not be reprogrammed. Looking forward to what BFG says, Z


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## protege26 (Jul 26, 2006)

Well, I have come to the conclusion that the people at BFG just don't pay attention. I emailed them and received a response that said go by the placard, and if they are the same size tires as original equipment, use that air pressure. 

Well, that isn't what I asked, but ok. Thanks for telling me what I already knew. So I called them (their phone menus are set up really odd...I fall under the recreational vechicle category..I thought that is what a 4wheeler is?) and I got a hold of a guy that laughed when I asked him almost. Then he realized what I was saying and admitted that it was odd that the placard and the max on the sidewall were the same. So he put me on hold and asked a supervisor, and came back and told me that they build in a few extra pounds of clearance into the tire past the max PSI listed on the sidewall, and that it was perfectly safe to run 35PSI cold in the tires, and that that would give me the maximum treadlife.

So that answers one question. I think we have figured out the other one. My light goes off with roughly 3 PSI difference overnight, however, if I have them filled at 35 cold the night before, the light will not go off the next morning. But if I have them at 34 cold, the light will go off. And this is with all temperatures being within a 5 degree window. So I am guessing that at 31 or so the alarm for the TPMS will go off. Guess I'll just make sure I keep them at 35 and see how it works out during the next rotation.

K.R.


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## Z_Rated (Apr 29, 2006)

Hope it works out for you. When I get a chance I'm going to check out the Long Trails myself. I really find it hard to imagine a set-up like that being intentionally put on any vehicle. If you remember, post back after the rotation. Later, Z


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## NPath (Dec 12, 2004)

I've set my pressure at 33PSI when it was close to freezing. 

Anyways, now that I think of it, why not just get some chalk and run a line across the treads. Do this on a dry day, take it for a short drive and see where the lines fade out. 

If you have a line in the middle of the tread, but none on the out treads, then that means under inflation. 

If you have lines on the outside treads but no line in the middle, over inflation. 

No lines seen at all, correct inflation.


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## Z_Rated (Apr 29, 2006)

FYI
While at the dealer for tailgate warranty parts I checked out some Long Trails...
LE 265-65 44psi max. SE 265-70 35psi max. The two trucks were locked so I didn't check the door sticker. That's just insane, no wonder so many people have issues with their TPMS's


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## BTF/PTM (Oct 19, 2006)

In general having less air pressure in a tire will actually result in less heat. Temperature and pressure are directly related in gases like air. Obviously there's an extreme case if your tires are drastically under inflated and you're running freeway speeds and the sidewalls are bulging way out. Anyway, running 5 or 6 PSI lower than "recommended" will not cause that condition so I don't think the extreme case applies to this discussion.

I like that chalk line idea, that's a great way to find an ideal running condition. There's no one rule to what the best pressure for your tires are. The way you drive, the roads you drive on, weather, blah blah blah, it all plays in. The best way to find that pressure is to test the tires for a few weeks. Pick a pressure, set the tires cold, check them after they're heated to running temperature, and check for tread wear patterns over the course of a few weeks. Also be aware that the best pressure for normal running is not necessarily the best pressure for max road grip or best rain traction. After you have a few weeks of testing and checking in each season, you can set up a pretty accurate inflation chart depending on what month it is.

It sounds like the TPMS is overrated, I think I'll just stick to checking my tires every week like I've always done with my vehicles.


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