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  1. #1

    Default tires 285/70/17 vs 2265/70/17

    I have a 2004 tahoe z 71 with stock 265/70/17 tires.i m thinkin of going with 285/70/17 tires.Will the MPG worsen? Will it it miss up the computor?im new to the forum.Thanks for the help.

  2. #2

    Default

    That change makes the overall diameter 3.3% smaller than stock. 32.7" down to 31.6" That will make the seedometer read too fast by 3.49% that means that at 60mph the speedo will read 62mph. The info I see says a change of over 3% should get the cpu reprogrammed, that isnt a very big deal but should probably be done by the dealer. Someone else on here may have more info but the numbers I quoted you are correct but I do not know DEFINITELY how much it will effect the cpu. Hope this helps, Good Luck
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  3. #3
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    Default

    Quote Originally Posted by bob13 View Post
    That change makes the overall diameter 3.3% smaller than stock. 32.7" down to 31.6" That will make the seedometer read too fast by 3.49% that means that at 60mph the speedo will read 62mph. The info I see says a change of over 3% should get the cpu reprogrammed, that isnt a very big deal but should probably be done by the dealer. Someone else on here may have more info but the numbers I quoted you are correct but I do not know DEFINITELY how much it will effect the cpu. Hope this helps, Good Luck
    I think you have it the wrong way 285/70/17 is a larger then diameter tire then stock.
    http://www.therangerstation.com/tech...nch_Tires.html

    Your speedo will read faster then what you are going by going up in size
    99 K1500 Suburban LT "THE BEAST"
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    285/75/16
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  4. #4

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    The 285 will not fit the stock wheel properly. Its too wide but it is done all the time. The wear problems that you will see is similar to over-inflation wear(worn more in the center). It will throw your speedo off by 2-3 miles at 65-70Mph. The faster you go the more it affects it faster and the slower you go the less it actually changes. We do it all the time and have not had any problems with the CPU, but a programmer will let you change the size in the CPU and is a cheap way to do it. As for the gas mileage you will probably see a little loss. Not much.
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  5. #5

    Default

    Sorry about that, in the title he had a different size than what he wrote about.

  6. #6

    Default

    It will be the same just in reverse. It is still over the 3% that is "usually" the benchmark for recalibrating. So basically at 62 mph the speedo will read 60mph. I had 285/75/16 on my 03 silverado that replaced the stock 265/75/16s, and I gotta say I did not have any wear issues. Just saying........

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