When/how/why max tire pressures raised from 35 PSI to 44 PSI?

Tires and Wheels (Mopar Hubcaps Too)

  1. dibbons

    dibbons Well-Known Member

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    It used to be maximum recommended passenger tire pressures were 35 PSI, now I understand they have jumped quite a bit to 44 PSI. What has changed in tire technology to justify the higher pressures? I still run my tires at 35 PSI , seems like 40 PSI or 44 PSI would be a pretty stiff ride.
     
  2. TrailBeast

    TrailBeast AKA Mopars4us on Youtube

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    That's what I thought when I got new tires for my Nissan truck (car tires) and they told me they were 60lb recommended.
    I asked the same question about the ride and they told me the rubber used was softer.
    They must have been right, because I couldn't tell any difference in the new ones with 60 over the old ones as far as ride stiffness.
     
  3. clifftt

    clifftt Well-Known Member

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    Most of the time, the vehicle manufacturere puts a tire pressure label on the driver's door jamb with their recommended pressure settings. The side of the tire shows "maximum rating", but vehicle weights vary. Use the recommendation by the vehicle manufacturer. The highest I've ever seen on a passenger car or truck is 40.
     
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    • RustyRatRod

      RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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      P metric sizes are "usually" a max of 35. Pressure varies with what load range the tire is. I have load range E on my truck. Their maximum pressure is 80 PSI. I run them at 60, because 80 would beat me to death in that old truck. That said, I have done both long term. Used the vehicle recommendations and used the max tire pressure for the given weight rating. I have found that the max pressure gives the most tread life. I will gladly give up a little ride quality for a tire that lasts longer.
       
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      • toolmanmike

        toolmanmike Moderator Staff Member FABO Gold Member

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        EPA and fuel mileage.
         
        Last edited: Nov 4, 2017
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        • TrailBeast

          TrailBeast AKA Mopars4us on Youtube

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          It was normal for a high load range tire to have a higher pressure, but I was surprised to see 60 recommended for a 215/70/15 car or light truck tire.
          Since my Nissan 720 pickup was a small truck I thought it was going to knock fillings in my teeth loose (especially on these streets)
          I always bitch about the streets here, but I don't think I ever gave a comparison as to just how bad they suck.
          I have PST 1.03 T bars and 215/60/15 tires up front with the bars cranked up 2 inches over stock height and have hit my K on the pavement multiple times.
          There is a right sweeping turn in the main street (4 lane) and a manhole cover in the left side of the right lane that is so inset into the street it slams the left suspension against the stop if you hit it during the corner.

          THEN they have the balls to try and use 80k of the streets fund for another bronze statue at the civic center of a cop with his hand on a kids head.
          Sometimes I feel like going down there and slapping some of those A holes on the counsel.
           
          Last edited: Nov 4, 2017
        • Mopar-Man

          Mopar-Man Big Block Better Burnout

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          Pretty sure all new vehicles are required to have tire pressure sensors now. With that being said, losing 5psi from 60-55 is a lot less variance than 35-30 in how the tire will perform. Also, but running much higher pressures you can run a thinner sidewall and save weight while decreasing rotational weight.
           
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          • bbrroowwnn

            bbrroowwnn never re member

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            I agree Rusty....I have E load rating on my truck also which are 10 ply and call for a max of 80 lbs....I have them on my truck because I haul 6 ton of coal every year for myself....not all in one trip of course......but I have had 2800 lbs. on already in my ram 1500 and those tire sidewalls barely squat.....Although the leaf springs were bottomed out......hahahah.....only going about 3 miles from the coal breaker though so no harm......great living in coal country when you burn coal
             
          • 4spdragtop

            4spdragtop CONGRATS NORTH AMERICA!

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            Funny Lori n I argue about how much psi to put in her tires. I say go with rating on tire. Lori says go with rating on door jamb sticker.She went and had new Toyos put on for winter so we revisited this "discussion". She asked at ths tire shop...he said to go with door jamb sticker psi!?!?!?
            How in the hell does the car know what tires its wearing? Lol
             
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            • odcics2

              odcics2 Well-Known Member

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              Your vehicle was engineered with the tire PSI in mind. Go with the door sticker, not the tire "max rating", if you want all your suspension parts to last! Ever price out a new steering rack? :mad:
               
            • brian6pac

              brian6pac Legandary Member Legendary Member

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              If you read the tire a load range E will say 3520 LBS @ 80 PSI, This doesn't mean 80 PSI if you have 1500 LBS on the tire. My old M/T say 20 PSI MAX at 1430 PSI. If I ran 20 PSI all the time the tires wear out in the middle because there is too much air pressure. The street rod weighed 2200 lbs total, that would be about 900 lbs on the rear total. You need to go by the tire wear and the weight not by what MAX is on the tire.
               
            • brian6pac

              brian6pac Legandary Member Legendary Member

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              Also if you run your car hard, like autocross you need to set your pressure per the tire tread temp across the tire, if the middle is hotter you need to lower the pressure, if the out sides are hotter you need to increase the pressure, if the outside is hotter you need to decrease camber and so on.
               
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              • Dfr360cuda

                Dfr360cuda Diagnosis... Plum Crazy.

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                image.png
                Trump = Miners best friend
                 
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                • Unconventional

                  Unconventional Well-Known Member

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                  Alright! Conveyors, crushers, screens, I can dig it! :thumbsup:
                   
                • Killer6

                  Killer6 Well-Known Member

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                  Not. Over half of the tires I mount every day, (whether I want to or not), have max pressures of 41,44,&50 PSI. That has absolutely nothing to do with the manufacturer's
                  recommended pressures, which are usually on the drivers door jamb, but some Krautwagons & others have them inside the fuel doors or the other doors etc. Superior
                  materials allow for more cold pressures which can allow the tires more flexibilty to accommodate applications. The load rating is the load rating, some tires are load rated
                  the same whether they have 35 or 44 PSI in them, even though the air is what is supporting the load,...the mfr will not over-rate the casing . This allows You to balance
                  the handling of the car by varying pressures, maintaining safe loading for a given tire size.
                  When it comes to LT tires, yes E load tires are rated for a max of 80 PSI, but because of the construction it will carry LESS load than a D load tire at the same pressures
                  that a D will hold. In other words, a D will carry more @55PSI than an E will carry @55PSI, just a little something to know.
                  And this time of year, I over-inflate all the cars I'm servicing a few pounds because eminent temp drops are always anticipated, figure 1PSI for every 10degF drop.
                  Drive safely this winter............................
                   
                • BigBlockMopar

                  BigBlockMopar BigBlockMember

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                  The cheap(er) passenger tires (Cooper / General / BFGoodrich) which are all to popular on older cars are limited by design to have much higher operating pressures then 35 psi.
                  Better tires can usually be filled with higher pressure.


                  You don't by any chance think wheel alignments are still to be done by the manual per factory recommendations?
                  No one drives around with bias-ply tires on their old cars anymore, except for a few resto-folks perhaps.
                  It's nice an old car still has its 40+ year old doorsticker, but it's long outdated because tire-technology has moved on. Radial tires simply need a different adjustment to operate at their designed best. Just like newer, better tires are designed to be run on higher pressures. Mainly to reduce rolling resistance and economical reasons.
                  Steering parts could perhaps live longer when using more pressure in the tires as it takes less force to push a wheel in a different direction, especially at low speeds.
                   
                • odcics2

                  odcics2 Well-Known Member

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                  Yeah, call me a dumb ass since I only spent 37 years in Chrysler Engineering, mostly in Chassis...
                   
                • dibbons

                  dibbons Well-Known Member

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                  I wonder if the performance difference in tire pressures diminish as pressure rises? i know its a big difference seeing 5 PSI compared to 10 PSI, but the performance of a tire probably does not change that much when we are comparing 30 PSI to 40 PSI. Once the tire gets more or less "filled" it won't expand that much more with more pressure (or get much stiffer), I don't think anyway.
                   
                • Tooljunkie

                  Tooljunkie King of cobble/master of the broken bolt FABO Gold Member

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                  This is another discussion we can find on many forums. If you did the math on sidewalls and knew the weight of your vehicle,a little math and you would have the pressure the tires could carry the car.
                  Door jamb for factory rated tires.
                  Deviate from factory size is a matter of preference. So is tire psi.
                  My power wagon runs 17 in the back and 22 in the front with a plow. 35x12.50-15 tires. Any more than that and tire print is the 2 center treads touching the road. At 45 psi this rig wont move on slick roads, as there isnt much of a contact pattern.

                  My wife’s pt cruiser, you cant tell any difference between 20 psi and 40 by looking at them. To me they always look flat.
                   
                • sireland67

                  sireland67 FABO Gold Member FABO Gold Member

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                  I am pretty sure my Ram 3500 the door sticker says 80 psi.
                  It did not take me long to lower the pressure down, it was UN-bearable to ride in empty.
                   
                • Bodyperson

                  Bodyperson Pedal to the metal FABO Gold Member

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                  I always run the max of what the tire says on passenger cars. Trucks, well you just gotta use your head. I adjust for loads. I run less in the rear than on the front with empty loads. I remember when it was 32# forever and then jumped to 35. You just gotta keep an eye on wear and adjust accordingly. Most tires suffer from under inflation wear from lack of maintenance.

                  A few years back my Dad was going on a trip across some desert areas. He asked me if he should get new tires first. He had some shoulder wear from under inflation. 35# on the side of the tire. We run em up to 40# and i told him to check em when it was really hot and don't let em go over 45#. He never adjusted them. He got over 30 miles to the gallon in a 302 fuel injected 1981 Lincoln Town Car. They must have been like bicycle tires out across that desert.

                  I'll have to agree with the EPA comment.
                   
                  Last edited: Nov 18, 2017
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