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  1. #1

    Default What size rims get better MPG? 18's or 20's? With Nitto TG's.

    Hey guys,

    I plan to upgrade my wheels and tires to somethign a little more beefy. I drive a ton and don't want to drain my current MPG to bad. What would get better MPG going with 18's or 20's on a 32" tire?

  2. #2
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    If you're definitely going with 32" tires no matter which wheels you choose,, then it would depend on what weighs more, the larger wheels or the amount of rubber they account for (replace) in the tire. Larger diameter wheels displace more rubber, but steel is generally heavier than rubber depending on sidewall thickness, so the tires on the 18"s should be lighter overall . If your tires happen to be "E" rated, then they might be close.
    Suffice to say you want the lightest combination you can get for better mpg.
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  3. #3

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    Awesome thanks man! I will have to do the homework to see what weighs more between the tires for the 18's or 20's. I will be going with an E rated tire I believe but not 100% sure. Can I get away with less of a rating than E? I am not even sure if Nitto TG's only come in E for that size. I'll have to definitely do my homework.

  4. #4
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    I have no idea what truck you have or the gvwr on it, or what weights you might haul in it.. I have a C-3500 1 ton 2wd & I'm puting D rated BFGs on it. I think I could have even gotten by with C rated since C is about 2800lb per tire which totals 11,200 (truck & load) but they might be marginal when I carry loads of rock. I have accidently carried 2 loads that were right around 5,000 lbs each, & if I'd had Cs on it they might not have made it lol

    ** If you can, just weigh one of each tire & each wheel &
    go with the lightest combination.
    Last edited by stephan; 12-20-2010 at 02:03 AM.

  5. #5

    Default

    Im no expert but I dont think there would be too much difference if the overall tire diameter is the same, in your case 32s. However tire width makes a difference as well as tread pattern. Obviously AT tires are going to rob more power. Also I read on another forum where those tires wont last long on a heavier truck so you have to get the proper rated tire!

  6. #6

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    First off, I will say I'm no expert either. I can't comment on 18" wheels and tires but I just replaced 275-55-20 summer/touring tires on my '07 Silverado and this is what I found. Factory tires were Goodyear Eagle LS-2.(summer/touring) I replaced them with Cooper Zeon LTZ's. Now the Cooper's are definitely a more aggressive tread design. My gas mileage dropped about 4 mpg on a recent highway trip. The Goodyear's have a 655 revs per mile and the Cooper's have a 652 revs per mile. The Cooper's also weigh 12 lbs. more per tire. I am attributing the lower gas mileage to the extra weight and tread design. You may also want to look at my situation as comparing apples to orange since the tread designs are so different but I hope this helps some.

  7. #7

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    I would agree really depends on weight and rotations.

  8. #8

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    I'm not sure if you have bought your Xmas gift yet, but here is what I have found that Nitto offers.
    *275/55/R20 117S 13/32 tread depth 2833lbs@50psi and 653 revs
    *285/60/R18 120S 13.6/32 tread depth 3086lbs@50psi and 664 revs
    LT285/60/R18E 123S 15.6/32 tread depth 3415lbs@80psi and 660revs

    With the little bit of experience that I have working in a tire shop, the 18's are going to last you longer, especially the 10ply (E), but takes more revs giving you worse gas mileage. Going with the 20's will probably give you a better ride since nitto offers it with a lower weight rating. If you have an HD, you can go with passenger rated tires (4ply, C), but as stated before you can have problems as well as the tires not lasting like they should. Another thing to look at is the cost of the tires. 18's have an odd reputation for costing more than 20's.

  9. #9

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    i was just looking at a set of the trial grapplers. in the 325/65/18. $350 a tire just little expensive for me. lol
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  10. #10
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    Hey,

    I would consider also thinking about the moment of inertia of each individual wheel. The lower the moment the less the amount of nonconservative forces there are. Much like a figure skater pulling her arms in that creates a faster spin the lower the moment of inertia is the easier it is to spin your wheel from a rest. At highway speeds this probably changes to a different calculation since I'm looking at moments from a static point of view.

    Good Luck!
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