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Thread: tire pressure conspiracy

  1. #1
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    Default tire pressure conspiracy

    I bought a new truck this year. Drove like a waterbed. I checked the tire pressures; 36 psi. I looked at the sidewalls of the tires; "max inflation pressure - 51 psi". I immediately proceeded to inflate the tires to the tire manufacturer's recommended pressure. Everything improved. Everything. I went to the dealer to express my displeasure and shock at sending a new unit down the road with such grossly underinflated tires. Hadn't they learned anything? Don't they know that improperly inflated tires wear faster? run hotter? degrade mileage? I was told by the Ford factory technician that 36 psi was the factory recommended pressure for my vehicle. "Look at the sticker in your door jamb," he says, and he was right, there's a sticker right there stating that 36 psi is where they should be. What? My wife comes home yesterday saying her 2014 Corolla's dash light was advising of an underinflated tire. I check the pressure. 31 psi. I look at the sidewall; 51 psi. What the hell's going on here?? I look in the door jamb... there's a sticker saying "35 psi". My son has a new set of tires put on his car from Discount Tire (a local chain). Same thing; wildly underinflated relative to the stated max pressure on the tire's sidewalls. Since when have third parties decided they know better than the folks who engineer, test, and manufacture the tires? I spent many years selling tire related products and we were annually visited by representatives from tire makers; Firestone, Goodyear, Carlisle, etc. Every one of them would admonish stridently that it was of the utmost importance to maintain tires at their stated max inflation pressures for all of the reasons I mentioned above and more. What's going on???
    Chuck Hancock

  2. #2
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    Default Re: tire pressure conspiracy

    At what pressure does your TPS system go off at. Thank Ford and Firestone.
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  3. #3
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    Default Re: tire pressure conspiracy

    What kinda truck? High tire pressures are often stipulated for 3/4 ton and one ton trucks. But the ride is brutal when the truck’s bed is empty.
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    Default Re: tire pressure conspiracy

    The recommended pressure would be 36psi cold. Once on the road, the tires will warm up and the air inside start to expand. How much, I have no idea, but the manufacturer is probably covering their butts by making sure your heated tires don't blow out.
    Inflating to 51psi cold and then running the car hot could result in blowouts.
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  5. #5
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    Default Re: tire pressure conspiracy

    It's not that complicated. "max inflation pressure - 51 psi" is not the same thing as "recommended inflation pressure" or "optimum inflation pressure". Just because the tires will take up to 51 psi doesn't mean you should inflate them to that pressure.
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  6. #6
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    Default Re: tire pressure conspiracy

    Use a columnar gauge, not a digital,
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  7. #7
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    Default Re: tire pressure conspiracy

    Chuck, a tire is inflated to match the load not some percentage of tire failure pressure. So if a tire can carry 2500 lbs at 50psi MAX pressure it doesnt need 50 psi at 1000lbs load. Do you have passenger or truck tires?

  8. #8
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    Default Re: tire pressure conspiracy

    That maximum tire pressure rating is also for maximum load. Look at the load rating for your tires. I suspect the maximum load for the four tires is MUCH more than the weight of your truck. Running the tires at their maximum rated pressure is going to cause excessive crown wear unless your truck is very heavily loaded. It will also give you less rubber on the road which will decrease traction, wet road steering and increase stopping distance.

  9. #9
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    Default Re: tire pressure conspiracy

    DON'T EVER INFLATE TIRES TO MAXIMUM PRESSURE


    By Tom and Ray Magliozzi
    Published: January 26, 1996


    Question - I was recently told by my local tire store manager, while fixing a leaky valve stem, that I should be inflating my tires to the pressure listed on the tire, not the pressure listed on the door or owner's manual. In the case of my Taurus, he inflated them to 41 psi. This seems excessive. What is the answer - the pressure on the tire or the pressure recommended by the manufacturer? - Jon
    RAY: The tire store manager told you that? The manager? Holy crowbar! There's a guy with his headlight firmly implanted in his taillight socket!
    TOM: The pressure printed on the sidewall of the tire is the maximum tire pressure. It's printed there as a warning, meaning "if you put more than this amount of air in this tire, it could blow up." It doesn't mean you're supposed to put that much air in there. What a knucklehead!
    RAY: It's like the maximum speed of your car. Your owner's manual may tell you that your car has an absolute top speed of 120 mph. That doesn't mean the manufacturer is recommending that you actually drive it 120 mph.
    TOM: The pressure printed in the owner's manual, on the driver's door pillar, or the glove box door is the recommended tire pressure. That's the pressure at which the car handles, rides, steers and brakes best. And unless you've changed tire sizes, that's the pressure you should always use. And for most cars, that pressure is between 28 and 35 psi.
    RAY: Under no circumstances should you inflate your tires to maximum pressure. Not only will you risk a blowout, but you'll diminish your ability to control the car because your handling and braking will be much, much worse.
    TOM: Not to mention the ride! How many scabs do you have on your head from bouncing up and hitting the ceiling since this guy overfilled your tires, Jon?
    Have a Holly Jolly Christmas🎅

  10. #10
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    Default Re: tire pressure conspiracy

    You could always be like Hunter S Thompson. He inflated his rental Cadillac’s tires to 90 or a 100 psi in “Fear and Loathing in Las Vegas”, if I remember correctly.

  11. #11
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    Default Re: tire pressure conspiracy

    as a corollary, if the recommended pressures are too soft and mushy for you, I could suggest raising them slightly until the truck feels the way you like. Those tyres can handle more pressure than they were originally inflated to, so you have headroom until it gets dangerous.
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  12. #12
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    Default Re: tire pressure conspiracy

    I remember seeing a picture in our local tyre dealer of marks showing the outline of a human body on the underside of a concrete roof.
    Some tyre fitter forgot about the tyre he was inflating, and was leaning over to remove the air line when it blew. RIP.
    150 lbs/sq.in can do a lot of damage.
    Chap in the local haulage yard was killed just walking past one of the lorries when a defective tyre blew- that one was at its recommended pressure.
    Another case was a woman driving past a burning lorry on the M1, who was killed when a tyre blew.
    Beware!
    Last edited by birlinn; 12-06-2018 at 05:22 AM.

  13. #13
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    Default Re: tire pressure conspiracy

    As has been said, the max pressure on the tire is just that - the max that the tire mfr believes is safe.

    What the car/truck mfr puts on the door jamb is an average - hard enough to handle loads, soft enough to not have people hate the ride.

    Thing is, required pressures will vary with the tire. A Nokian or other aggressive snow tire will need higher pressures than say a Pirelli summer tire (unless it's a high performance tire). TP monitors are with us because people are too lazy and/or clueless to check tire pressures - pay attention to the pressure!
    "If it ain't broke, you're not trying." - Red Green

  14. #14

    Default Re: tire pressure conspiracy

    You could also bend over, put the air chuck where the sun doesn't shine, inflate and wait to see what maximum pressure is, or was, but the ride will be bumpier. Conspiracy must be POTUS TRUMP'S fault.

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    Default Re: tire pressure conspiracy

    Did I miss the memo wherein the BROTM declared december to be Dumbass Automotive Threads Month?

    Next up: defrosting windshields with kettles of boiling water
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  16. #16
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    Default Re: tire pressure conspiracy

    Quote Originally Posted by Figment View Post
    Did I miss the memo wherein the BROTM declared december to be Dumbass Automotive Threads Month?

    Next up: defrosting windshields with kettles of boiling water
    That only works when the temp is below zero F & even better after you've used a steel snow shovel to scrape the windshield off.
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  17. #17
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    Default Re: tire pressure conspiracy

    My daughter got some new truck tires for her 2001 Toyota pickup. The tires are a bit oversized and I was wondering why it hopped around so much on the road. Max pressure on the tire was somewhere around 60 psi and they were inflated to 65 psi, the tire installer did this. Door jam pressure for those tires was 28-32. You could have put these tires on a F350 they would have been perfect. Brought the psi down to recommended pressure and it was much better.

    I’ve come across this misconception with people who pump their mtn bike tires up to 50psi when 35 is plenty For Their Weight.

  18. #18
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    Default Re: tire pressure conspiracy

    Some of the confusion may be due to the recommendations from some sites to keep trailer tires at max psi. Although I'm not sure I agree with that recommendation. Seems better to weigh each load and inflate per manufacturer rec.

    E.g. West Marine:

    Maintain pressure at the maximum PSI recommended on the tire’s sidewall for cool running, load-carrying ability and lowest rolling resistance.

    Discount Tire:

    A trailer tire should be inflated to the maximum inflation designated on the sidewall of the tire to provide the full load carrying capacity.
    Last edited by bluedog225; 12-06-2018 at 11:59 AM.

  19. #19
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    Default Re: tire pressure conspiracy

    Always go with the vehicle manufacturers spec. It's there for a reason.
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  20. #20
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    Default Re: tire pressure conspiracy

    Quote Originally Posted by LeeG View Post
    My daughter got some new truck tires for her 2001 Toyota pickup. The tires are a bit oversized and I was wondering why it hopped around so much on the road. Max pressure on the tire was somewhere around 60 psi and they were inflated to 65 psi, the tire installer did this. Door jam pressure for those tires was 28-32. You could have put these tires on a F350 they would have been perfect. Brought the psi down to recommended pressure and it was much better.

    I’ve come across this misconception with people who pump their mtn bike tires up to 50psi when 35 is plenty For Their Weight.
    I always run 50-60 psi in my MTB tires for two reasons:

    1) I like a rounded carcass with firm shoulders, and I want it to stay the EXACT shape I want. As close as possible, anyway. It helps tremendously with contact patch feel at speed, say above 20mph.

    2) I do NOT want to blow a tire landing from a jump, and under inflated tires bend rims, pop beads, and/or explode. My buddies were just telling me about a new jump they built. It’s about 30 feet from lip to lip.
    No, I haven’t been thinking of going there. I’ve already been. It’s glorious. No, I haven’t thought about jumping it.

    Peace,
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    P.S. I only run 90 in my road tires. I ran 120-150 on the track.

  21. #21
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    Default Re: tire pressure conspiracy

    Has everyone forgotten the Ford Explorer tire debacle already?
    "The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails."
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  22. #22
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    Default Re: tire pressure conspiracy

    Quote Originally Posted by Canoez View Post
    Has everyone forgotten the Ford Explorer tire debacle already?
    I thought that would be the end of Firestone but they're still kickin'.
    -----------------

    And now for the inevitable drift...

    Nitrogen? For auto tires? Who thought that scam up?
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  23. #23
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    Default Re: tire pressure conspiracy

    Quote Originally Posted by John of Phoenix View Post
    I thought that would be the end of Firestone but they're still kickin'.
    -----------------

    And now for the inevitable drift...

    Nitrogen? For auto tires? Who thought that scam up?
    Well, I use ~78% Nitrogen virtually all of the time...
    "The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails."
    -William A. Ward



  24. #24
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    Default Re: tire pressure conspiracy

    Tire pressure for best grip and performance are different than pressures required for maximum fuel efficiency and will also differ according to tread compound and construction or intended use (snow vs high performance summer tires), load and weather conditions and tradeoffs between best wear characteristics, ride comfort, best fuel mileage or best wet or dry weather performance.

    There is no one "best" tire pressure as all are compromises depending on the desired end result. Certain pressures will yield better (or less) grip but less (or better) fuel economy, tread life or poorer wear patterns, etc. Pressure selected for extreme high performance use (as when tracking) are frequently actually best when lower than those required for normal street use but may result in higher wear, poorer fuel economy, different ride characteristics etc. And so it goes.
    Last edited by Lew Barrett; 12-06-2018 at 11:30 AM.
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  25. #25
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    Default Re: tire pressure conspiracy

    Heard of insurance claims assessors checking tyre pressures after a shunt. Any excuse to duck out!
    Go by the book.

  26. #26
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    Default Re: tire pressure conspiracy

    Well there's a lot of advise and opinion here. Lots good, some,...well,..fun. Amongst the long list of vehicles I've owned over the last 42 years, I've maintained max tire inflation pressures on all of them and have achieved, by any measure, great performance. I agree there's mixed opinion on the subject from varied parties. I guess I'm just surprised that I've logged over half a million miles on so many different tires and different vehicles and only now am become aware of this schism. I must be getting old. Thanks for all the input everyone.
    Chuck Hancock

  27. #27
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    Default Re: tire pressure conspiracy

    Thank you, Canoez. I couldn't remember the model of Fords. The cars rode rough so Ford specified softly inflated tires. Said tire pressures contributed to rollovers. IIRC, the whole mess was exacerbated by labor strife at the tire mfr, but I could be wrong about the last part.
    Seems like I see a lot more people inflating their tires since the sensors in the wheels became available. Is this a case of detecting a long ignored problem, or of false positives creating an imaginary problem?

  28. #28
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    Default Re: tire pressure conspiracy

    Quote Originally Posted by David W Pratt View Post
    Seems like I see a lot more people inflating their tires since the sensors in the wheels became available. Is this a case of detecting a long ignored problem, or of false positives creating an imaginary problem?
    Probably a little of both. I know that my wife's CRV has a TPMS system that's very sensitive and temperature change often causes it to trigger. My Civic has a different system that doesn't monitor the pressure, exactly, but needs to be reset when tires are rotated or you inflate the tires. It reacts unusually sometimes, but works well.

    For those that think "max" is a good pressure, I think you'll find that the vehicle manufacturers have a different take. Posts #9, 13 and 19 sum things up nicely.
    "The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails."
    -William A. Ward



  29. #29
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    Default Re: tire pressure conspiracy

    In my experience it's a largely imaginary problem.

    After thanksgiving dinner, the boy reports that his check-engine light has been on for a couple of days, so maybe he should take grandpa's BMW for his black friday shopping adventure.
    Well, no, maybe you should take your car in to get checked out in the morning, dumbass.
    Of course it was the tire pressure sensors not the check-engine light. The cold weather dropped the pressure juuust below the threshold of the sensor. Fussy PITA.
    No adversary is worse than bad advice.

  30. #30
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    Default Re: tire pressure conspiracy

    If you had the tyres at 'max recommended pressure' in the old rear-engined Hillman Imp, you would soon be off the road and into the scenery.
    The manufacturer's recommendations of 15 lbs front, 30 lbs rear were there for VERY good reasons.

    ETA: Chevy Corvair was similar- 15 front, 28 rear. For similar reasons.
    Last edited by birlinn; 12-06-2018 at 01:11 PM.

  31. #31
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    Default Re: tire pressure conspiracy

    Tire pressure also affects tread wear -- an over-inflated tire will wear faster at the center of the treat than it will at the edges, and vice versa with under-inflation. Proper inflation will give you longer even tread wear.

    Temperature also matters. I recently drove from NYC when temperatures were around 50°F -- a few days later in central Maine, when the temperature was 3°F, my tires were down 10 pounds of pressure.

  32. #32
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    Default Re: tire pressure conspiracy

    It is my understanding that a tire's maximum rated load is achieved at 36 PSI for modern tires. The maximum inflation pressure is often much higher ( 41, 50 psi, etc.),doesn't add to its rated load carrying ability, but it is safe to run them there. You may get better handling, or lower rolling resistance, etc., but no guarantee.

    I hope Katherine will chime in and tell me if I am wrong.

    I went through the exercise of re-engineering the tires on my old beater Subaru Loyale. The stock tires are no longer made: 165SR-13 with maximum rated load at 32 PSI. They were replaced by 165/80 R13, with a maximum load at 36 PSI. Recommended tire pressures were 28 PSI around town, and 32 PSI at high speeds or under heavy loads. So that means that the "new" tires should be run at 36 psi, to achieve maximum load rating.

    Now, decades later, 165/80-R13's are no longer available. The choice is 175/70-R13, which doesn't have quite the same capacity, but is close, so should be run at 36 PSI. In snow tires, even this size is hard to find. 155/80-R13 is more available. but has a much lower maximum load rating. So, what to do? I run the small tires, at maximum pressure (36 psi +), only in winter, and not at high speeds or heavy loads. So far, it is working for me.

  33. #33
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    Default Re: tire pressure conspiracy

    When I ran a Lotus Europa, 2 lbs up or down on the recommended rear tyre pressures made a perceptible change to the handling.
    Go by the book!

  34. #34
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    Default Re: tire pressure conspiracy

    The old rule of thumb when changing to a different sized tire was:
    1) Inflate to the recommended pressure from the door jamb when tires are cold
    2) Take the car out and drive it hard for about 20 minutes.
    3) Jump out and immediately check the hot tire pressures.

    If the hot pressure is exactly 10% higher than the cold pressure, then you're OK. If it's more than 10% then the cold pressure was too low. If less than 10%, then it was too high. Retest as necessary.
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  35. #35
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    Default Re: tire pressure conspiracy

    Lew nailed it.

    The vehicle manufacture has no idea what kind of tires are on the vehicle after it leaves the showroom, and tire manufacturers have no clue what vehicle their tires may be installed on.

    So darn it, people will have to make informed decisions and not depend on a label in a door jamb.
    "Simple minds discuss people, Average minds discuss things, and Great minds discuss ideas".

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