Dumb tire pressure question.

[Greatscott]

The recommended tire pressure on the door panel says 39, the tire says 50 (factory tires). Never seen such a miss match between the two. Do you split the difference?


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[hpiguy]

I'd bet the 50psi on the sidewall is likely the max pressure if you look closely.

https://www.safercar.gov/Vehicle+Sho...ire%20sidewall.

[dugans]

I concur- tires typically state the max pressure.
The door label states the manufacturer recommended pressure- which is a good starting point but NOT always what you want.


I typically run 3 or 4 psi over OEM in front and OEM or 1 or 2 more psi in the rear, but again it depends on vehicle, driving conditions and driving style.


Also this is different in extreme conditions, like loose sand or, dare I say it - rock crawling.


Final note- try to set the pressure when the tire is "cold" - not after driving far. Just driving a couple of miles can heat the tires up enough for pressure to go up a few psi.

[BJoe]

Yup, concur on the 50psi being Max for the tires while 39psi being what’s recommended for the vehicle.

[Panther6834]

ALWAYS go by what the vehicle manufacturer states.

It doesn't matter what the tire manufacturer states...tires can be placed on any vehicle, but the tire manufacturer knows NOTHING about the vehicle's weight, is weight balance...the pressure listed on the type of the tire's max, which will be higher than almost any vehicle's max.


~ More peace, love, and kindness would make the world a much better place

[OnTheTrail]

Always go by the door jam spec plate.

[BJoe]

I usually aim for 32psi or higher, but everything I’ve owned has been sub-4000lbs too, I would be careful of some manufacturer specs since Ford had been recommending 28psi on the Explorers even though it was below what Firestone’s recommended minimum was.

[indybama]

We always run 35psi in cars n light duty trucks (f150 for ex). In the heavy duty (f250 f350) we run closer to 45-50psi

[Phildirt]

Yep 35 cold in every tire I’ve ever owned and that is a lot of tires lol. The only time I’ve ever run a specific pressure or even thought about it is on a commercial vehicle.

[ScaleLifeNewbie]

I would do what the vehicle says.

We run 50-55 psi in our F150, but it has heavy duty 8 ply tires and i imagine your not towing 10k+ pounds lmao.


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[Phildirt]

Originally Posted by ScaleLifeNewbie

I would do what the vehicle says.

We run 50-55 psi in our F150, but it has heavy duty 8 ply tires and i imagine your not towing 10k+ pounds lmao.


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So you contradict yourself there. The door sticker on an F150 says 35psi, not 55psi. So you’re not doing what the vehicle says, you’re doing what the tire says (maybe, still sounds high, I’ve run up to 12 ply and never seen one with 55 recommended cold on a light truck)

[meatmonkey]

Tire sidewall is max pressure for max load. Doorjamb pressure is manufacturers recommended tire pressure.

[ScaleLifeNewbie]

Originally Posted by Phildirt

So you contradict yourself there. The door sticker on an F150 says 35psi, not 55psi. So you’re not doing what the vehicle says, you’re doing what the tire says (maybe, still sounds high, I’ve run up to 12 ply and never seen one with 55 recommended cold on a light truck)

You are right, I did. But, when I said what the door sticker says I’m talking about with factory tires like in Scotts case and not pulling a lot of weight all day everyday.

We have never ran anything under 50 psi on any of our trucks, no matter if it was a 1 ton, 3/4 ton or a 1/2 ton.

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[Mike Flea]

Originally Posted by OnTheTrail

Always go by the door jam spec plate.

I respectfully disagree.


My RAM 1500 originally came with 17's, hence the jamb tag states 35psi for the 17's. Previous owner changed to 20's, and the correct pressure per CDJ, is 40psi, so unless you do a little research per the manufacturer, you may be running your tires at the wrong pressure.

[ScaleLifeNewbie]

Originally Posted by Mike Flea

I respectfully disagree.


My RAM 1500 originally came with 17's, hence the jamb tag states 35psi for the 17's. Previous owner changed to 20's, and the correct pressure per CDJ, is 40psi, so unless you do a little research per the manufacturer, you may be running your tires at the wrong pressure.

Yep, go by the door jamb with factory tires, but go with the tire manufacturer when you get new tires


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[OnTheTrail]

Originally Posted by Mike Flea

I respectfully disagree.


My RAM 1500 originally came with 17's, hence the jamb tag states 35psi for the 17's. Previous owner changed to 20's, and the correct pressure per CDJ, is 40psi, so unless you do a little research per the manufacturer, you may be running your tires at the wrong pressure.

I stand corrected. I was referring to stock wheels/stock tire size. Anything outside of stock, then no, door jam may not be the answer.

[TIREBUSTER]

My opinion, ignore the door jamb unless it's a passenger vehicle then yes follow the door jamb but go 2 pounds over the recommended pressure so you have a little more leeway when they cool down after driving so its not so close to triggering the TPMS light. There's more to the 2 pounds over as well but I'm not gonna go that far into it. As for LT vehicles and some suvs, if youre running stock 4 ply tires from the factory on a 1/2 ton then minimum of 40 in the front and if not towing then 35 in the rear is fine. We see rounded shoulders alot when we run the recommended 35 in the front of customers vehicles and the rear has less weight than the front which means you don't need as much as to handle the load. As far as all these 3/4 and 1 tons, if youre not towing, the recommended 65-80 depending on the vehicle is wayyyy more than needed in the rear and will alot of times cause ride disturbances in the seat and/or wear in the center of the tire from being overinflated. 50-60 psi is plenty in the front if not towing. On any vehicle, if you do tow or even if you dont, if you really want to narrow it down, go find a scale and get each axle weight then do the math to find the correct air pressure to hold that load. And as someone stated in another post, you can check them while they're warm, but try not to adjust your tires until they are cold which I believe is recommended 2-3 hours after driving. And if you want or need to run lower air than what the TPMS is set for then find a shop with a decent TPMS tool that has an obdII with it and they can go in and change the setting to match the air pressure you want/need to run. And if you want to keep it simple and not get it down to the T, then just run 35 in most passenger cars, 40-45 in 1/2 tons and 50-55 in 3/4 to 1 tons and adjust for towing if necessary. Holy shit, sorry for such a long post. And sorry if it doesn't make sense in some parts. Its harder for me to type it than if I was able to someone in person. If you want to get real specific you can but otherwise you can jusg follow the basic guidelines or whatever you want to call it like some of the people on this post have already talked about. Any questions just ask. We can get much more technical haha

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[Alexander_0_1]

^^^

This eased my mind.

I have 2 old Fords a 2001 f150 supercrew with 18x9"s, and E rated Duratracs, and a 2003 F150 on 20x12"s with 35" F rated gladiator X comp MTs. I have 40-42psi in both trucks.

Yes! Both trucks feel noticeably rougher than when they had factories on.

[ferp420]

Every tire is different for every rig the numbers on the door are just for stock wheels and tires if your new tires are bigger than stock run lower air pressure if there smaller than stock run higher pressure personally on my daily driver I run around 22psi cause the tires are a lot bigger than the car was designed to run and that's were everything is happy also there all terrain truck tires and most of my driving is on dirt roads so my needs aren't the same as the average driver my truck runs 50psi but it doesn't start with out a load on it there is no one right tire pressure there's even differences between brands one brand might hold up the vehicle on 30psi another brand tire might want 35psi for the same size tire for the same vehicle It just depends on how the tire is made I had a set of tires that were so stiff they didn't need air at all even with the truck loaded and still wore out the center of the tire

I use 3 observations to set my tire pressure i look at the sidewall of the tire if it looks right then I drive the rig
If the rig drives like a boat I know I have too little tire pressure and if the rig feels bouncy I know I have too much and if you really want to get in to it you can do a tire print test to see if your tread is hitting the ground evenly since I don't have a glass observation station that's the best I can do
You know you have it right when your tires ware evenly

[hpiguy]

^^Yep, used a spray bottle and a dry parking lot back in the day to get my pressures right for a 33x12.50 on a 15x10 rim.