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Tire air pressure question?

Discussion in 'Truck & Equipment Repair' started by NYH1, Jan 11, 2014.

  1. NYH1

    NYH1 Senior Member
    Messages: 129

    Not really a repair question...

    My truck in my sig below, has Goodyear Wrangler DuraTrac tires, size 285/70-17. They're load range D (3200 lbs.), 65 psi max. The tread was 18/32" deep when they were new about a year ago. They have a little over 7000 miles on them now and they've worn down nice and evenly to about 16/32". That was with Dodge's factory recommended 36 psi air pressure.

    Now that I have my Fisher SD 7.5' plow, probably close to 550 lbs. (plow & mount) and 480 lbs. ballast weight against the tail gate. What should I run my tire pressure at with the plow on and ballast weight in the back?

    Thanks, NYH1.
     
  2. SnoFarmer

    SnoFarmer PlowSite Fanatic
    from N,E. MN
    Messages: 8,550

    "They're load range D (3200 lbs.), 65 psi max."

    Your going to want to run them at the max psi that is stated on the sidewall.
     
    Last edited: Jan 12, 2014
  3. Whiffyspark

    Whiffyspark 2000 Club Member
    from SOMD
    Messages: 2,402

    Is this a 1500?
     
  4. SnoFarmer

    SnoFarmer PlowSite Fanatic
    from N,E. MN
    Messages: 8,550

    That's what he said.
    and his sig states
    "
    2007 Dodge Ram 1500 Quad Cab SLT 4x4, Hemi, auto tranny, 3:92 LSD, 285/70-17 Goodyear Wrangler DuraTrac w/Fisher SD 7.5 ft. Plow"

     
  5. NYH1

    NYH1 Senior Member
    Messages: 129

    Yes, my truck is a 1500 (1/2 ton). The door sticker says to inflate my tires to 36 psi. when cold. Running them at 36/38 psi. has given me a nice even wear pattern across the tire, down to 16/32" from the original 18/32" tread depth in the first 7000 plus miles I've put on them in the year I've had them.

    I kind of figured that since I'm putting a little over 1000 lbs. of weight in and on my truck I might be better off increasing the air pressure in the tires. Is there any way to tell what I should raise my tire pressure to when I have my plow on and the ballast weight in?

    Thanks, NYH1.
     
  6. johnhenry1933

    johnhenry1933 Senior Member
    Messages: 256

    Rather than going by the door info, I would go by the tire info (tires could have been swapped/upgraded).

    With that much weight on a little 1/2 ton, and working on top of it, I would max out...at 65 psi.

    Off topic, if you had a heavier truck, even just a 3/4 ton, you may have more latitude (my light truck ties hold 80 psi).
     
  7. Whiffyspark

    Whiffyspark 2000 Club Member
    from SOMD
    Messages: 2,402

    I'd put 50 in them. No reason to max them out. It'll do nothing but ride like sh t

    Your door sticker says 36 because you're supposed to have prated tires on it. D's are lt tires.
     
  8. johnhenry1933

    johnhenry1933 Senior Member
    Messages: 256

    I'd be less concerned about "ride" than a blowout and traction. This a work truck, not a pleasure cruise.

    And BTW, the 930 lbs. estimated (550 + 480) does not account for passenger(s), fuel, tools, salt, etc., which could quickly add another 500+.

    You may not need to max out, but I think you need to be close to it.
     
  9. Whiffyspark

    Whiffyspark 2000 Club Member
    from SOMD
    Messages: 2,402

    It's a half ton truck its not going to matter. He doesnt have nearly enough weight for it to matter

    He puts max psi in them there's not enough weight on that truck to give him any traction. I Dont even run max psi in my 3/4 with a plow, d range tires.

    Most half tons come with p rated tires hence the 36psi in door. D range is generally for 3/4 tons or 1 tons that Dont tow
     
  10. SnoFarmer

    SnoFarmer PlowSite Fanatic
    from N,E. MN
    Messages: 8,550

    You could always weight your front then your rear axles when loaded to see how heavy you are.

    With load range "D" tires they have a softer sidewall than "e". You want to have a hard enough tire so when you hit or go over curbs, hit pot holes etc etc it does not damage the tire or rim when plowing.
    We run a set of "d" tires on one 3/4 ton plow rig. they have like a 3300lb(guesstamant) load capacity we run them at max psi, we have been for 4years and the tires are doing great.

    Experience says to run them at max psi.
    as the mfg doesn't know what size tire your running or what load your carrying, front or rear.
     
    Last edited: Jan 13, 2014
  11. stone74

    stone74 Member
    Messages: 52

     
  12. 32vld

    32vld Senior Member
    from LI, NY
    Messages: 620

    I bring some age to this question of how much PSI.

    Back in the 60's and 70's a lot of people that can not think for themselves would put in the PSI that was on the door jamb sticker about 26-28 lbs or the maximum PSI that was on the tire sidewalls 32 lbs.

    As radials were used more and more in the mid 1970's and 1980's along with looking to get better tire tread life wear and gas mileage people were ignoring the door jamb sticker and going with the 35 lb on the side wall.

    From the 1990's on car and light trucks had maximum side wall PSI of 44 lbs for many tires. Though door jamb PSI had not changed much through the years.

    What I have found today is the door jamb info will still give the lowest MPG and tread life. Though where in the past running a tire at the maximum PSI rating on the sidewall had no adverse impact is no longer so today Running at today's higher side wall PSI can adversely effect the tire tread wear.

    I have seen this on autos and light trucks. My Suburban/1500 has tires that have a maximum PSI rating of 44 PSI.

    My Suburban rides empty most of the time. When I tired running the tires at 44 lbs the tires were wearing out in the center of the tread faster then on the ends of the thread. Running the tires at the factories recommended psi caused the opposite uneven wear of the thread.

    Being you have added a lot of weight I would split the difference between the 36 and the 65 and try 50 lbs. Treadwear is a good indication of good tire pressure.


    I figured that if you payload is 2,000 lbs and you are carrying half of your maximum payload makes sense to increase your PSI half way between where you are at 36 lb and the maximum of 65. Difference is 29 lb. Half of the diff is 14.5 lb. 36 + 14 = 50 lb.

     
    Last edited: Jan 13, 2014
  13. SnoFarmer

    SnoFarmer PlowSite Fanatic
    from N,E. MN
    Messages: 8,550

    lol,
    How young do you think we are?
    I'm in my 50's.




    Even today with stock tires and using tires recommended by the MFG it's best to fallow the recommendations on the sticker in the door jam.
    Really? Even if 65-70psi was recommended for carrying a load on a 3/4 or 1ton?
    I'm not buying it...
    Some over inflated their tires in a vain attempt to get better millage during the oil embargo.


    Even when they used load range "e" tires?
    Because a tire isn't going to carry a heavy load for very long at that low psi with out heating up and failing.

    cars and trucks, 1/2 to 1 tones all had different psi recommendation even way, way back in the stone age.
    Some had "p" "D" or "e" even back then.


    He needs to mach his load to the psi that will allow the tire to perform with the weight he is carrying.

    On the tire it has the max load in pounds at a stated psi.

    If it's not the stock tire, size wise or weight ratting. the sticker goes out the window.
    I'm sure your "P" rated tires do have such a low weight ratting and psi requirements.
    Sounds right.
    my "d" rated tires are wearing very uniformly and they offer great traction at the max psi.
    Plow trucks are sometimes much heaver than we think they are. Snow, ice ,our gear, salt, sand, plows all add up quickly.

    In this case under inflation will wear then out quickly and it could subject the tire and wheel to damage.

    I wouldn't be worried about over inflation then loaded up to go plowing.
    This is age and experience talking...;)
     
  14. jasonv

    jasonv PlowSite.com Addict
    from kannada
    Messages: 1,114

    Hey SnoFarmer;

    From the op "They're load range D (3200 lbs.), 65 psi max."
    That's 3200 pounds PER TIRE. So putting those tires to 65 PSI would match up to a total front end weight of 6400 pounds, which is more than the weight of his ENTIRE TRUCK, including the plow, driver, fuel, and whatever crap he has in the back.

    There are charts indicating what the proper inflation pressure is, based on the tire size and the load.

    http://cache.toyotires.com/sites/default/files/imce/LoadInflation_Table_P-LT_102913.pdf

    His tires are 285/70R17, so page 22 (A12) near the bottom, if his front end WITH THE PLOW, weighs less than 4210 pounds, he can stick to the door pressure (36 psi).

    Also note that the bigger tires (285 vs a more normal 245 width) will support more weight at the same pressure. So though his 285's can take 2105 pounds each at 35 psi, a 245 might only take 1500 pounds at the same pressure -- the difference is over 500 pounds per tire, or enough to support the weight of a rather HEAVY plow, so because of just the tires by themselves, he may not need to go above the door sticker. Note though, that I don't know what his factory tire size actually is, so he will have to look up the loads in the charts himself, or better yet, weigh it, in fact weight the two axles individually.
     
    Last edited: Jan 13, 2014
  15. johnhenry1933

    johnhenry1933 Senior Member
    Messages: 256

    Not to continue this discussion ad nauseum:

    He has already stated the door sticker (Dodge) recommends 36 psi. With that load at that low a psi I would think he bursts his sidewalls in no time.

    Real world physics dictate the fuller (within range) the better. And as SnoFarmer stated, what about potholes and curbs with that minimally inflated tire?

    I guess at the end of the day the op should start at 60...or at 40, and try driving and plowing incrementally until he finds his happy medium (proper inflation given the load and traction).

    But I've never worn out the sidewall, or bent a rim with a tire inflated to 80, 90 or 95% of max psi.
     
  16. jasonv

    jasonv PlowSite.com Addict
    from kannada
    Messages: 1,114

    Reading helps, I suggest you actually try it rather than picking apart a small portion of a statement while ignoring all of the very very necessary CONTEXT.
     
  17. Whiffyspark

    Whiffyspark 2000 Club Member
    from SOMD
    Messages: 2,402

    No he won't lol.

    1000 lbs is nothing. Thats probably not even over payload.

    36 is for P rated tires. His tires are not OEM. D tires are 8 ply
     
  18. Whiffyspark

    Whiffyspark 2000 Club Member
    from SOMD
    Messages: 2,402

    Double post
     
  19. NYH1

    NYH1 Senior Member
    Messages: 129

    My truck came with 275/60-20 wheels and tires. The first thing I did was buy a set of factory 17" wheels (actually have two pairs now) and tires. I changed then as soon as I could. The 20" tires sucked.

    I ran 40 psi. in my current tires for a few weeks last fall and really liked the way it handled over 36 psi. in them. When I was having my tires rotated (free rotation) I asked the guy about running them at 40 psi. instead of 36 psi. He said if I ran more pressure in them then I needed I could wear out the center of the tire faster then the outside edges, as mentioned. He said to put more air pressure in them when I had a load in the truck or when towing.

    So now I'm trying to figure out how much air pressure to put in them when I have my plow and ballast weight without putting to much in. Safety and the truck functioning properly is my main concern. Not worried about ride. Maybe I'll try 50 psi. I just wish there was a way to tell if it was correct or not.

    Thanks, NYH1.
     
  20. jasonv

    jasonv PlowSite.com Addict
    from kannada
    Messages: 1,114

    There *IS*. But it depends on knowing the weights on the axles. Then you just look it up in the charts I linked to in post #14 of this thread.