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I have salvaged NEW tires LT225/75R16 from a 2011 E350 dully and want to mount them on a 2014 E250, existing E250 tires are LT245/75R16. What would be my confidence level that they would function approximately the same ?

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Tires sizes are fun. Here's what's going on:

  • your current tires are 245 mm wide, your new tires are 225 mm wide.
  • both sets of tires have the sidewall 75% of the width of the tire.
  • both sets of tires fit on a 16 inch wheel

Here's what it means:

  • your new tires are skinnier than what they are replacing. This provides better grip in winter conditions (same weight on a smaller tire contact patch means more pressure applied to the pavement), but less grip in summer conditions (smaller tire contact patch)
  • although your new tires are skinnier, they still have the same aspect ratio (75%), meaning they are overall smaller by about 4% here's the tire calculator I use. This means your speedometer and odometer will be off by about 4%. Since these tires are smaller, you will be going 4% SLOWER than what your speedometer is reporting (you'll really be going 48 when it says 50), and you would have travelled 4% less distance than what the odometer says (you would have really travelled a distance of 288 when it reports 300, making you think you are getting better gas mileage).
  • your new tires will still handle about the same as your old tires, except for the 2 points above.

Personally, I like to stick to tires that keep my instruments reporting accurately. I do change tire sizes on some of my vehicles, but the new tires sizes are still the same size around as the old ones, meaning I get to tune my contact patch without messing up my odometer or speedometer.

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