Tire PSI question

[Couver]

Just had some new tires installed on my truck. Goodyear says go with what the manufacture says. In my case the door says 32 psi.
Installer put them to 38 saying that’s what they do on their personal truck. Is a higher PSI they use due to more of a load? I haul very little other than four passengers and that is rare. I don’t want weird wear or traction.

I think I know the answer does anyone see what I may be missing?

Goodyear Workhorse Ht

 

[thewoodlands]

Just had some new tires installed on my truck. Goodyear says go with what the manufacture says. In my case the door says 32 psi.
Installer put them to 38 saying that’s what they do on their personal truck. Is a higher PSI they use due to more of a load? I haul very little other than four passengers and that is rare. I don’t want weird wear or traction.

I think I know the answer does anyone see what I may be missing?

Goodyear Workhorse Ht

I'm not sure if this is correct but I go with the info from the door.

 

[thewoodlands]

Tire PSI or Vehicle Manufacturer PSI: What’s the Difference? | Emergency Response

maclintruckandtrailer.com

 

[ABMax24]

Generally go with the door sticker. Pickups can vary though, as inflation pressures are often based on the vehicle hauling the maximum load. It also varies if your tires are not the stock size. For instance my door sticker says 65psi front 80psi rear, but my current tires are rated for 65 psi max, and wear the best with the fronts at 60 psi and the rears at 45psi when empty, and I bump the rears to 55psi for towing.

You can also watch the tread for wear, more wear in the center indicates over inflation, wear on the shoulders indicates under inflation.

 

[Ashful]

ABMax24 nailed it. Always go with the door sticker, with the following exceptions:

1. If door sticker spec is higher than max inflation rating of tire, you can only go to max inflation rating. Of course, then your tires are probably also under-spec for your GVWR, as the two are related.

2. If running a tire with a higher ply rating than that originally spec'd for your vehicle, you may find you need to bump PSI slightly higher (eg. your installer's recommendation to go 38 PSI instead of 32 PSI... assuming the guy actually knows what he's doing, and assuming your new tires are indeed higher ply rating than OEM).

3. If you know you're not going to be hauling anywhere near GVWR on a heavy truck, running slightly lower can give better tire wear and ride when unloaded... as long as you actually set them back to door sticker rating before loading up. This is a dangerous game, not usually recommended for casual operators. It also doesn't usually apply to passenger vehicles and lighter trucks, where curb weight + fuel and passengers is the larger fraction of GVWR.

 

[mellow]

Put chalk on the tires to figure out your best PSI.

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[Couver]

Thank you all for the replies! With it being so warm here I took the tires down to 34. It feels like there is a bit more grip. Weird how a few PSI can make a difference. I use another place to change my oil (they do tires too) I am curious to see what they do.

 

[ABMax24]

1. If door sticker spec is higher than max inflation rating of tire, you can only go to max inflation rating. Of course, then your tires are probably also under-spec for your GVWR, as the two are related.

I guess something I should have clarified is my tires in my example are not stock sized. The factory 275/70R18 Load Range E tires are rated for 3,580lbs at 80 psi inflation pressure. My current Toyo RT's in 37x12.5R18 are rated for 3,970lbs at 65psi.

 

[RockyMtnGriz]

The technically correct answer is that you should refer to the load and inflation tables to determine the correct pressure. Note that the tables give what I consider to be the minimum inflation pressure for a given load. Pressures can be increased from that value for various reasons (sustained high speeds, handling, etc.). This looks like a good reference, and it has load and inflation tables at the end:

https://www.toyotires.com/media/2125/application_of_load_inflation_tables_20170203.pdf

Common sense needs to come into play as well, especially where pickups are concerned. If there's only one value given on the door sticker, it'll be good for the FULL rated load. An empty pickup with the tires inflated to the door sticker value of possibly 80 psi will be an absolute terror to drive in the snow for example. A sedan fully loaded to the approved capacity will safely carry the load with the tires at the door sticker value but will be better in every way with a higher pressure if the tires will allow it. Best is to come up with the values for empty and full, and work between those as needed, particularly with trucks. Older standard cab pickups were often much heavier in the front when empty and would be best with a higher pressure in the front (when empty). Current luxo six pack trucks, not as much.

My FWD sedan for example, empty in the snow, 26 or so works pretty well in the rear. I usually leave the front at 30 since that's where the weight is and the tires hold up better that way on winding roads. The door sticker of 30 plus 5 pounds seems to work best for running with a lot of twisty roads most of the time. Full load or autocross day, 50 seems to be the ticket - just gotta make damn sure I let them down before I hit snow or ice without a heavy load!

Lastly, use a good tire gauge or your efforts may be in vain!

 

[Ashful]

Lastly, use a good tire gauge or your efforts may be in vain!

This has been a huge PITA for me. Maybe 20 years ago, I noticed that no two of my tire gauges were giving me the same reading, and since that time I've invested in and cursed many gauges. It's really surprising how bad some can be, and most come with no specification on their accuracy, let alone a calibration cert.

If using analog gauges, be damn sure you're using them inside their 25% to 75% zone, if not even 33% - 66%. I have 2" dial gauges in full scales of 15, 30, 60, 100 and 160 PSI for this reason, most with both straight and angle heads, so I can always grab the one who's 50% reading is closest to my target pressure. Even then, many are horribly inaccurate. The worst are the cheap pistol-grip jobs with the 160 PSI gauge mounted atop, I find they're often off by a good 5 - 10 PSI (up to 30%!) at typical tire pressures.

 

[weee123]

Heavier ply tires require more psi in them. When I use to run E-rated tires on a lighter truck I would run 40 psi in them compared to the stock 35.

If running similar tires to stock just run whats on the door jam. If your tires aren’t even rated to the spec on the door jam I’m assuming you just cheaped out on your tires.

I have 1 tire pressure gauge stick that I trust. I’ve been using it for 10 years and have done my own tests on it by comparing it to various vehicles tpms readings and it always checks out.

 

[Wooden Head]

After years of using all kinds and forms of PSI gauges and having the vary as much as 15 PSI, I bought a JACO Elite Pro digital pressure gauge. It has been flawless in function. It was $30 but no more guessing what the real pressure is.

 

[Woodcutter Tom]

I just purchased a JACO Elite Pro. Might even get it in the mail today. I got tired of cheap gauges that gave unreliable readings. How can a guy put the proper air pressure in a tire if he can't rely on his gauge??

 

[Poindexter]

@ABMax24 and @Ashful are killing it in this thread. The only tire pressure gauges I trust are dial type that hold a reading and have a release valve. I want the midpoint reading on the gauge to be 30-35 psi, so range on the dial 0-75 or 80 psi.

The free tire pressure gauge from your bank or barber shop with the sliding white plastic rod is worse than useless. Don't accept it as even a free gift. If you must, smile, say thank you and drop it in the nearest trash receptacle after you leave the establishment.

In general, all other things being equal, a higher pressure will give your tire better side bite, while a slightly lower pressure will give the same tire better front bite. If you are competing with a front engine rear while drive vehicle on dry pavement, this is easy. If you have a pick up truck in 4WD on snow you need all the bites all the time.

You can't go very far down this rabbit hole without needing a pyrometer to measure the temperature of the tread blocks, inner, middle and outer on all four tires very rapidly when you pit and the tires are still hot.

For the OP, I would go with 32psi on all four corners for now since the truck is rarely used at capacity. Next, take pictures of the treads with your phone every 1k miles or so. Just back up (zoom out) far enough that you have enough vehicle in the picture to know which corner you are looking at, but put the focus point on the center tread block. Most likely, on a lightly loaded truck, you will first see wear on the inner tread bands of the front tires. In general truck manufacturers put a lot of camber on the fronts, they tip the tops of the front tires in towards the engine a few degrees, so the fool thing with no load in the bed can turn a corner without a lot of drama. It makes the truck easy to drive, but it is very hard on the inner tread blocks of the front tires. You get to 5k miles, rotate front to rear on both sides, get on with your life.

When you get to 10k miles and it is time to rotate again, it might be time to see how much it will cost to rotate left-> right instead of front -> rear. If you have asymmetric (directional) treads, you will have to dismount and remount all four tires to rotate L->R, but that will very likely put very good tread blocks in the high wear position at (usual suspect) front/inner, and be less expensive than replacing all four tires.

The chalk method advocated by @mellow is extremely effective, but you can sometimes see results in 10-15 feet and then have no usable data if you roll the vehicle 50 feet. I didn't watch the video, BTDT got the T shirt. I'll go start the video. Mellow, well done. With a different vehicle that dude could be competitive at Sonoma. I personally would chalk up about 75% of the tread blocks. No big braking, no burnouts, good advice. But I would also only roll about ten feet and be looking for chalk to already be missing from the front inners - long before the chalk was gone from the front outers.

In general if the OP leaves his tires at 38 psi (s)he is probably going to have perfectly adequate side bite and likely less wear on the front inner tread blocks compared to running at 32 psi x 4 corners. Gas mileage should be pretty good. Front bite on the rear axle in 2WD on dry pavement is going to be abysmal. Performance (all parameters) on snow and ice (@38psi) will invoke the poorer tasting anatomy of an angry donkey.

One compromise would be to run 38psi summer and 32psi winter.

Good luck and best wishes.

 

[Poindexter]

An alternative to the chalk method is liquid white shoe polish, as shown below on the rear corners. With significant time and effort I was able to place 275mm tread width tires under all 4 corners of my 2004 GTO (VY Monaro), compared to the factory 245mm tread width. The one thing I learned at my one day at Sonoma is I didn't (and still don't) make enough money to be competitive at Sonoma. I was, as a bachelor, able to keep the car clean.