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Tire Pressure??

cutehumorcutehumor Member Posts: 137
Does anyone know the right tire pressure for
P175 70R 13 tires? I got new tires the other day. I used my tire gauge two of them were 38 psi, the other two around 36psi. Since their not all equal, I was wondering if anyone knows what is the right pressure for this particular tire size. thanks.


  • armtdmarmtdm Member Posts: 2,057
    That will tell you the maximaum cold pressure that can be used. The front door lable will give the manufacturer's recommended pressure which is primarily for comfort. Over 30 years of driving I find that by inflating tires to about 3-4 lbs less then the max at cold will give extended tire life, no outside edge wear and better handling. The price is a slighlty harder ride. So for a 35 psi max I use 32 and for a 44 PSI Max I use about 41-42.
  • adc100adc100 Member Posts: 1,521
    I now have my daughter's car. All the tires have slight "dimples" on the side walls. They are approx 1 to 2 inches in diameter. Some of the tires have two or three. I don't believe they were there from new. I'm going to the tire place I do business with to check them out. The brand is -get ready- "Premium Radial". Oh boy!! Can't go back to origional dealer as this was in Mississippi- I live in Pa.

  • t56gen3t56gen3 Member Posts: 6
    I have seen several different tires do this. They bulge out on the sidewall--it sort of looks like a blister. It's usually from hitting curbs while driving or parking. I can't blame it all on just "inexpensive" tires, as I have seen it on Michelins too. You will have to replace them. They just don't have very strong sidewalls. Just FYI.
  • adc100adc100 Member Posts: 1,521
    they are sucked in. I don't think it is from damage. I believe they came through that way!!!
  • fish8fish8 Member Posts: 2,282
    A tires pressure should be based on the manufactures recommendation and not what is stated on the side of the tire. The pressure on the side is the MAX the tire can handle. Using the rule "inflating tires to about 3-4 lbs less then the max" is not a good rule. Tires are designed to run at a certain pressure depending on the car and truck. Manufactures recommend the proper tire pressure based on the design of the vehicle. That is why the lable located on you door jam (or somewhere else in your car) specifies a exact pressure to use, no "3-4 lbs less than max". If your tires are not original Equip, the tire manufactures website will specify the correct pressure.
  • swschradswschrad Member Posts: 2,171
    some tire pros I trust say this is due to the manufacturing techniques now in use... basically the belts overlap slightly that make up the tire casing, and so do the rubber sections, and not necessarily all of them at the same place, since that leads to a big imbalance. the result is when all the sidewalls and bump edges etc. are molded on, just about all tires have a visual irregularity on the sidewalls. these are not supposed to affect the integrity of the tire, they just look funny if you shine up the tires.

    now, if it looks like you have a little volcano of rubber coming up on the side, or a big watery-looking blister that shimmies as you run your finger across it, you DO have a big problem possibly happening... a delamination of the casing. any tire tech who can tell flat from inflated should be able to tell at a glance and a finger-poke if you have an issue ready to be adjusted onto a new tire under warranty.
  • armtdmarmtdm Member Posts: 2,057
    Sorry, manufacturers recommendations are based upon providing the best possible ride, not necessarily the best mileage or performance. Thus a tire rated at 35 PSI max when cold the manufacturer usually will say 28 PSI wheas if you run the tires at 32 PSI you will get much better mileage out of the tire and it will not wear on the outside edges but the ride will be slightly stiffer. And, you are not exceeding the tire max if you are at 32 PSI cold.
  • q45manq45man Member Posts: 416
    Say the tire has a max load of 1521 pounds at 44 psi [a 95 rated 225/60/15] equals 34.57 pounds of support per psi. The correct pressure would be the static [sitting still loaded] weight on the tire say 1100 pounds divided by 34.57 or 31.8 psi.
    It is prudent to add some pressure to protect the tire when you turn as up to 400 pounds of additional weight could be placed on the tire during the turn. 3-4 psi is enough [unless you're turning all the time. Generally the front tires have the highest load so they are the critical ones except when car and trunk is loaded down to max then the loads may be equal so best policy is to have equal pressure front and rear. Certain rear drive loaded [1000 extra pounds] luxosports may need higher rear pressures under certain conditions.
  • daltam4evrdaltam4evr Member Posts: 1
    I just bought a '95 4Runner and it has the big 31.5" 15R tires. I'm being told by the seller that HE was told to keep them at only 24psi, but he said he runs them at 28. Is 24psi about right due to the fact that they're larger tires? Any help appreciated.
  • carnut30carnut30 Member Posts: 51
    Some mfgrs. such as Subaru and Mazda recommend reasonable tire pressures. For models with 59-62% weight on the front, pressures of 33 psig front and 27 psig rear are a good compromise. SAAB was crazy with the 9000 in calling for 27 front, 30 rear. Tires should have pressures proportional to the weight on them, as in one of the posts above. Equal pressures on any car with a big % weight at one end are an example of dumbness left over from the days of rwd cars which were nearly 50:50% under load.
  • ryanbabryanbab Member Posts: 7,240
    check the tire and look at the max rating

    24psi for a truck tire is kinda low. I am running LT285/75/R16 BFG's on my truck at 52PSI max is 65psi
  • marcbmarcb Member Posts: 152
    ..remarks seem to explain my experience with my Mazda MPV.

    When I got my van last summer, Mazda originally had the tire pressure at 32lbs. Winter, they made a tire pressure "recall" and reset that to 35lbs, and sent us a door sticker. I liked the slight improvement it made on handling.

    So Spring, I set it to 40lbs. Immediately the van felt a lot more substantial, more stable, leaned less on turns, and improved mileage.

    I had been planning to slowly reduce tire pressure to compromise handling and ride. If g45man is right, 38 or 39lbs should be within 3 to 4 lbs the recommended pressure.

    But since I love to take turns fast (more than one person has commented on this), I may keep 40lbs yet.

    Can some tire experts share their insight on how safe(or unsafe) this is?
  • carnut30carnut30 Member Posts: 51
    ...have the answer. Do not exceed the max pressure printed on the tire. This is when the tire is cold. The only other penalty is that the middle of the tire tread will wear out before the outside parts. Since the tire as a whole will last longer at higher pressures, even this should not be a big problem.
  • marcbmarcb Member Posts: 152
    thnx carnut. guess i got confused with the tire max and the car manufacturers recommended max.

    so im ok at 40lbs then - now i'm happy.

    ...hmmm :-O maybe i should try bumping that up and see what happens.
  • dpwestlakedpwestlake Member Posts: 207
    My 95 Saab 900SE 5-door has 3 recommended pressures depending on load and max speed.

    The minimum is 28 PSI the maximum is 38 psi. same pressure front and rear. I use 36 psi at all 4 corners.
  • carnut30carnut30 Member Posts: 51
    ...the boink!, boink, boink! from the rear over every bump, and the oversteer on hard bumpy turns as the overinflated rears jump from crest to crest. And a good thing your car has ABS. If you like the feel of 36 psi at the front, 28-30 psi at the rear would make sense. Believe me, you are not the only one. An old friend in a brand new Honda Accord was jumping around with 40 psi in all 4. This is just the dumbness of the dealership in not changing the shipping pressure!! My latest used 1995 SVX was delivered with its new Yokohama AVS dB tires sort of randomly inflated to 37-40 psi.
  • barnonebarnone Member Posts: 118
    yah, my honda dealer insisted on 35psi where the door sticker says 26psi

    i wonder why...
  • blackgtpblackgtp Member Posts: 19
    For most people, the proper tire pressure is exactly what the manufacturer states. Most people do not know enough to be changing things on their cars. For the rest who know enough, I need not say another word.
  • nanny17nanny17 Member Posts: 2
    Hi, I have a 00 Grand Prix and I was wondering if 30psi is to low? Also how often should you rotate the tires? Thanks and enjoy your weekend, Nanny.
  • q45manq45man Member Posts: 416
    on the tire max pressure and the weight on the tire...some manufacturers are more conservative than others [safety factor] vs the need to make the car ride softly.
    29 psi is only 66% of max safe COLD pressure for most tires [44 psi] something like 35 psi COLD is 80%.....generally a 3 psi increase [over tire placard] will result in slighty improved tire life and mpg!
    If you are concerned with best handling in curves you must get more envolved at calculate the correct pressure.
  • Mr_ShiftrightMr_Shiftright Member Posts: 64,481
    And buy a GOOD gauge and keep it in the glovebox. Gas station gauges are notoriously inaccurate, as are the cheapo "pen type" gauges you buy for $3.

    I think on a FWD car tire rotation (front to back, not criss-cross) is a good idea. I'm not sure about the mileage, but if you're a hard driver with a FWD car with some HP, every 5,000 wouldn't be too soon IMO.
  • windowphobe6windowphobe6 Member Posts: 765
    I am distressed to report that when the dealership rotated the tires on my 626 this summer (at the 7800-mile mark), they did not adjust the pressures to either the Mazda recommendation (32 front, 26 rear) or my usual practice (34 front, 30 rear); the car came back to me with the newly-emplaced front tires 4 psi lower than the rear, which suggests that they didn't look at the pressures at all.
  • yooper53yooper53 Member Posts: 286
    No big surprise there. About a year and a half ago I took mine to the Ford dealer for tire rotation. Anyway I check t.p. twice a week so I KNOW what they're at. Front, 31 psi, rear 34 psi. Anyway I checked them and found them at front, 34 psi, rear, 31 psi. I was p-o'd and went to the service manager who informed me that they always put 35 psi all around to which I replied , "Fine, then my fronts are 4# low and the backs are 1# low. My point? They didn't even put a pressure gauge to the tires. So I'm supposed to trust them with things critical?
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