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P Tires and MPG

Discussion in '80-Series Tech' started by landtoy80, Mar 10, 2004.

  1. landtoy80

    landtoy80

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    The wife is going put some miles on the 80 this year. At 12 mpg and $2.00+ gas, I need better MPG's.
    If I go with P rated tires and light weight 265/80/16 or 275/70/16 (stock size, right?) should I get the 16 mpg range I had before the heavy LT285/80/16 lug tires?
    Does the 265/80 have the same diameter as the 275/70?
     
  2. floatinghat

    floatinghat

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    I check every tank, resently I up'd the pressure from 28psi to 45psi in my 265/75/16 BFG at's mpg went from 13.25 to 15.53 ish (only two tanks) same general routes. I won't say it handles like she' s on rails, but the handling has also improved. I think the 235/80 is about the same rolling diameter and the 275/70/16 so might help.

    andre
     
  3. cruiserdan

    cruiserdan SupportingVendor Emeritus Moderator

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    265 x .8 = 212 x 2 = 424 / 25.4 = 16.69 + 16 = 32.69 inches

    275 x .7 = 192.5 x2 = 385 / 25.4 = 15.15 + 16 = 31.15 inches

    For optimum road comfort and MPG potential you would be well served by the OEM Michelin LTX's in 275/70/16
     
  4. landtoy80

    landtoy80

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    Are they P or LT rated?
     
  5. landtoy80

    landtoy80

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    OOPPPS I ment 265/75/16 not 265/80
     
  6. Junk

    Junk

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    [quote author=cruiserdan link=board=2;threadid=12909;start=msg118919#msg118919 date=1078966311]
    265 x .8 = 212 x 2 = 424 / 25.4 = 16.69 + 16 = 32.69 inches

    275 x .7 = 192.5 x2 = 385 / 25.4 = 15.15 + 16 = 31.15 inches

    For optimum road comfort and MPG potential you would be well served by the OEM Michelin LTX's in 275/70/16
    [/quote]

    Cdan, no offense dude (wow, did I just type that? :slap:), but you know you can't go by the mfg provided measurements. Every company lies through their teeth about the measurements.
     
  7. Darwood

    Darwood

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    If you can go by the posted real measurements that many companies provide it's intersting to note that the metric sized tires are closer to their calculated size than the standard sized tires are.

    For example this PDF: BFG MT Specs
     
  8. landtoy80

    landtoy80

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    I was thinking about the 265/75/16 as there is more selection and cheaper tires don't come in 275/70/16.
     
  9. landtoy80

    landtoy80

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    The 270/70 diameter is 31.3
    264/75 31.8

    Cooper Discovery S/T 265/75 is 31.5
     
  10. SteveLCetc

    SteveLCetc

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    I'd second the motion for the MIchelin LTX A/T's like Dan said. I actually got over a hundred thousand miles on a set on my 1985 4runner. They're really pretty good off-road and snow tires to boot.
     
  11. landtoy80

    landtoy80

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    The LTX are a bit to $$$
    I just need a cheap set for a bout a year till I can get the wife a vehicle. Then the wimmpy tires go in the trash.

    I hope if I spend the $$$ on new smalle P tires I will gain some MPG.
     
  12. hpantier

    hpantier

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    Maybe post int the wanted section for a set...there has to be someone who wants to go to larger tires that would happily unload their stock ones on you. Maybe pretty cheap...Just a thought.
     
  13. landtoy80

    landtoy80

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    The only problem with used tires is if they are not worn even on all four it is hard on the VC.
    The last owner of my 80 was into used tires. I had to replace the t-cace when I got it. I am done with used tires on 80's. Take-off would be OK but I don't see many new 2004 FZJ80's on the road in this part of the world.
     
  14. hpantier

    hpantier

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    well you're up on me, i don't see ANY 2004 FZJ80's out here... :)

    i understand about the used tires...it was just a suggestion.
     
  15. Gauge

    Gauge

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    Wait a minute....I'm surprised that no one is jumping all over Floating Hat's post. You mean to tell me that increasing tire pressure from 28 to 45psi gains you a 17% increase in fuel economy?!?

    I have never heard of anything remotely like this for any car or truck. When I think of all the money I wasted on split fire plugs, oil additives and the like to gain a 3 or 4 percent increase. What a waste! Now you tell me all I had to do was put more air in my tires? WTF ???

    Has anyone else tried this with similar results?
     
  16. mtycruiser

    mtycruiser

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    Here goes my 2 cents:
    Bigger diameter: more rolling resistance
    wider tire : more rolling resistance
    bigger diameter : more distance for every tire revolution = better MPG = less acceleration
    I just change tires from P275/70/16 Michelin Cross Terrain ( 32.1 diam ) to BFG AT KO's LT285/75/16 ( 32.9 diam ) I use 32 psi cold on both tires.
    After two tanks, my MPG is still the same after adjusting for Difference in diameter ( new tires 5.4% bigger diam.) I'm getting 14-14.2 MPG in city driving, still need to play with more tire pressure to see if I can squeeze some more MPG without sacrificing too much on ride comfort.
    SB
     
  17. landtoy80

    landtoy80

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    Well with mtycruser's results, going down won't help.
    I just aired up to 58 lbs from 43 lbs.
    The wife just took the 80 out of town, I execpt a phone call any time now saying the ride is too hard :-[

    When I got the LT285, the LT285 weighed about the same as the P270 and rim together.
    The LT is a 8ply and the P is a 4ly.

    My next step for better MPG's will be to try synthetic air.
    THe only problem is I don't have the new synthetic compressor from Sears yet.
    The stuff is to $$$ at parts store.

    Maybe I will try Helium ;)
     
  18. mtycruiser

    mtycruiser

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    One of the best tools to improve on MPG is a "light foot" while acelerating and "reasonable" speed on the highway. There's a lot of diffrence in consumption between 65mph and 75 mph.
    In my opinion pressure in the 40's and over is waaaaay too high and should only be used when very heavily loaded.
     
  19. landtoy80

    landtoy80

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    <In my opinion pressure in the 40's and over is waaaaay too high and should only be used when very heavily loaded.>
    Does it mater what the max pressure is? If max is 35 then it is too high but what about 85psi max?
     
  20. landtank

    landtank SILVER Star

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    I've always guaged tire pressure by how the vehicle handles and tire wear. I run 45lbs in both my BFG ATs and ProComp X-Terrains. No issues in tha last 90k.
     
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