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Upsized tires on 17 in rims

Discussion in '2002 - 2005 Ford Thunderbird' started by DL1834, Jan 7, 2019.

  1. Does anyone have experience with using larger tires? I have search prior threads with no luck for a solid answer. I want to put white walls on the 17 inch rims without putting out massive amount of money for them. I found 225-60-R17
    The diameter of the tire changes from the stock 26.3 to 27.6 with sidewall changing to 4.6 to 5.3. I don't seem to see anything out there that shows the limitations of the 02-05 wheel allowances.
    Skizix Savage and Tee for 2 like this.
  2. Johnvins

    Johnvins Well-Known Member Lifetime Donor

    When I was a teenager, I would go to the garage and get old tires and have them mounted. I wanted to see what the clearance was, even drive around to see it it scraped the inner wheel well. I would push it to the limit going up to the biggest tires that fix comfortable, on my '70 Cuda, before I actually made a purchase.
    Skizix Savage likes this.
  3. LOL and if I was a teenager again I'd do that!
    Skizix Savage and Elaineinwa like this.
  4. vinnie

    vinnie Aways Learning Lifetime Donor

    I dont see how the diameter increases as stock width is 235mm and yours would be only 225mm?
    Maybe I'm not reading it right?
    Skizix Savage likes this.
  5. I attached a pdf of the calculated value changes.

    Attached Files:

    Tee for 2 likes this.
  6. Xssive

    Xssive Active Member Platinum Donor

    The aspic ratio changed from 50 to 60 and that is your sidwall.
  7. DrSarabi

    DrSarabi Well-Known Member Gold Donor

    The larger circumference tire would probably fit in the wheel well, so long as the new wheels have the same offset.
    Your speedometer will read lower than you actual speed. For example if it reads 60 mph you will actually be going 63 mph.
    The taller sidewall will give a softer ride and steering. And you profile is an inch narrower so you have less contact with the road.
    When I changed to 18" wheels, I found a tire that kept the circumference within .1 of the original. The sidewalls were shorter, but it really improved the handling performance. It rides like a sportscar, not like a sedan but that is what I wanted.
  8. vinnie

    vinnie Aways Learning Lifetime Donor

    The aspect ratio is not the sidewall, 225/235 is sidewall width in millimeters.
  9. The rims I am going to be using are from a Ford Taurus SHO, I will have to determine the offset to see if it differs from the stock Tbird rims. Both are 17 inch but that doesn't mean the offset are the same.
  10. Sierra977

    Sierra977 Well-Known Member Lifetime Donor

    Here's a tire size comparator that may be of assistance. (My car has 245/45R18 on front and 275/40R18 on rear. They are 18 inch tires mounted on Jaguar wheels to maintain correct 60 offset.)


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