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Changing tire size

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by t75atc, May 16, 2010.

  1. t75atc

    t75atc New Member

    I have factory 17" polished aluminum wheel on my 2010 Sierra Crew Cab. Might have run across a deal on factory 20" chrome wheels and tires. What would I need to do to make the speedometer/odometer correct with the new size wheels and tires? Change a speed sensor at/in the transmission? Reprogram computer?
    Thanks!
    Brian
  2. chucknorris

    chucknorris Rockstar 100 Posts

    um no, i dont think so, as long as the tire size (265 or something) stays the same im pretty sure ur speedo will to.
    off note, i have the 20' chrome wheels, but im not a fan of the chrome, id rather have the 18' off the z71 package. looks like it was meant for off roading more.
  3. Ohu812

    Ohu812 New Member

  4. pvcableguy

    pvcableguy New Member

    if you go from a stock 17" tire p245/70r/17...to p275/55r 20"....the width of the tire doesnt matter...its the height..so going from 17's to 20's....your speedometer with be ruffly 5 mph faster than what it shows....until you reprogram it for the 20"s
  5. silveradotrailblazer

    silveradotrailblazer Epic Member 5+ Years ROTM Winner 5000 Posts

    As long as the tire outside diameter stays about the same you shouldnt have to do anything. My wifes Trailblazer came with 16" wheels ( I forget what the factory tire size was) and we installed 20" wheels with 275/45-20 tires which were about the same outside diameter as the factory tires and we didnt have to do anything to the truck.
  6. 2COR517

    2COR517 Epic Member 5+ Years 1000 Posts

    Wow. Another bunch of guys that don't understand tire sizes.

    Don't worry about correcting for different size tires until you get them and know what the new size is.

    If you get tires with an outside diameter within 5% of the stock tires, I wouldn't worry about it all.
  7. cain73

    cain73 Rockstar


    This is correct information. As long as the tires are the same circumference it will be the same travel and you won't need to adjust for tire size. If however you go from a circumference of say 28" to one of 33", you will need to reprogram for that change. I have a Cortex programmer for the Chevy and it allows me to adjust tune as well as for tire size changes. There are many out there that will compensate if you need it.
  8. adampaul1964

    adampaul1964 Epic Member 5+ Years ROTM Winner 1000 Posts


    33" circumference wil give you a tire that's about 10" tall!! Surely you mean DIAMETER

    Stock 17" tires are usually 265/70/17 which are 31.5" tall. Stock 20" tires are usually 275/55/20 which are 31.8" tall. So you can interchange them without affecting the speedometer.
  9. cain73

    cain73 Rockstar


    LOL exactly, diameter. I always get screwed up when pie or pi is involved lol

    but yeah you can go .3" without a problem. When you go from 31-35 you better adjust for it. radar guns will win over your incorrect speedo every time.
  10. adampaul1964

    adampaul1964 Epic Member 5+ Years ROTM Winner 1000 Posts


    Hmmm...I love pie!:lol:

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