Swapping tire size

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Skiharleydoo, Nov 28, 2022.

  1. Skiharleydoo

    Skiharleydoo Bobtail Member

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    I currently have 11R22.5 tires on my 2022 Western Star 5700XE.
    I’m going to swap to 295/75R22.5.

    How much will my speedometer be off?

    Can a dealer change the settings on the ECM to correct the speedometer?
     
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  3. Gridaxe5588

    Gridaxe5588 Bobtail Member

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    Nov 23, 2022
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    Running the same on my 16 Cascadia and mine is only off 1 MPH.
     
  4. 062

    062 Road Train Member

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    Vehicle Speed Calculator
    It'll vary a little depending on specs and speed, but around 2-4mph. Yes dealer should be able to help.
     
    Skiharleydoo Thanks this.
  5. aussiejosh

    aussiejosh Road Train Member

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    Depends on the diameter if there is not much difference you'll find it will hardly make a difference. I would not worry to much about it. As the police will usually allow most vehicles a certain percentage over the speed limit anyway.
     
  6. Skiharleydoo

    Skiharleydoo Bobtail Member

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    Jun 12, 2017
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    My speedometer was 3mph off with the smaller tires. Updated the ECM to 509 revaluations per mile. Problem solved.
     
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