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? on tire load ratings

Discussion in '40- & 55-Series Tech' started by lovetoski, Aug 28, 2003.

  1. lovetoski

    lovetoski SILVER Star

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    OK, I guess all of you might be tired of tire questions, but I've searched every BB I can find, including mfgr websites, and haven't yet found an answer to my question - which is simply, what difference does the load rating make on a tire?

    For example a typical 33X10.50 R15 has a load range C, and a rating of ~2300 pounds. While a 255X85R16 is usually a load range D, with a rating of ~3000lbs. Some of the 285/75R16's have a rating of ~3500 lbs or more. All of these are "similar" in terms of diameter and width.

    My fj60 fully loaded might get close to the load rating for a 33X10.50/15, but not the other two options. Keeping price out of the equation, assuming that the same tire was available in all three sizes, would the load rating be a reason to choose one size over the other?

    Thanks for the help!

    Doug Graham
    1987 fj60, 265,000
     
  2. Degnol

    Degnol

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    The only thing I can tell you is the higher the load rating the rougher the tire rides. I had a 1/2 ton 'Burb and put load range D tires to replace the C range and it felt like they were full of concrete. The higher the load range the thicker and or more numerous the belts are.
    IMO I do everything I can to soften the ride in my '40.
    HTH
    Ed Long
     
  3. dinkleberry

    dinkleberry

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    I think it has to do with sidewall strength. The D loads are always at 55-85 lbs psi, while the C-range are under 45lbs.

    The D's are on the larger trucks (f-450, duelies...)

    And they do ride and balance even worse that muds.
     
  4. Rice

    Rice SILVER Star

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    Ditto. You likely wouldn't want to run load rated (D) tires unless you had concerns about a tire being cut. I ran them on my 2500 suburban but only because of heavy towing loads. They do include more plys which means heavier and harder to balance.
     
  5. 78 One owner

    78 One owner

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    It's a boxers or briefs thing. On the road they're heavier, stiffer, and harder to balance, granted. On the flip side, offroad: they have stonger sidewalls and more plies for protection against rocks, handle lowered air pressures with less damage, are harder to dismount or break bead. And the obvious greater load carrying capacity.
     
  6. lovetoski

    lovetoski SILVER Star

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    Actually, I was hoping that a higher load rating meant a tougher sidewall - as that's where my tires have typically failed when out having fun...since it's a 60, and is "plush" compared to a 40, I don't mind a harsher ride on weekdays to gain some ruggedness off-road.

    How much of the harsher ride is due to the higher pressure, versus more durable tire construction?

    Thanks guys for the quick response!

    Doug Graham
     
  7. 78 One owner

    78 One owner

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    As with any tire the ride is adjustable with air pressure. If you play your PSI up and down to find the sweet spot you'll not even know they're Ds. When airing down for off road you'll have less "squish" or bulge at the PSI you've used in a C. Drop a little more to find the "sweet spot".
     
  8. dinkleberry

    dinkleberry

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    The harsher ride can be from the high pressure, but the extra plys makes the tire more out of balance.

    On the plus side, I think that some brands you can actually drive while flat for miles without major sidewall damage. Especially driving a "lightweight" FJ as opposed to a 15000 GVW full size PU.
     
  9. s79bj40

    s79bj40

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    dads been running cooper disco S/Ts on his 100 and b4 on his 105 which are D rated. He loves them and says that on the road the extra sidewall stiffness actually helps the handling and cornering. That and he hasn't had a sidewall puncture with them yet. (although hes only driven 60000k on them)

    Sam