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Thread: Tire circumference variants coding

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    Tire circumference variants coding

    Doing some spelunking into the instruments coding . Found a byte with multiple tire circumference variants.i have a set of 18" detroits id like to put on my car but are slightly different rolling radius. like a 7 revolution difference per mile.
    either way is there a way to determine value of each variant ?im new so go easy

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    Benevolent Dictator Uwe's Avatar
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    Quote Originally Posted by dillenger1 View Post
    Doing some spelunking into the instruments coding . Found a byte with multiple tire circumference variants.i have a set of 18" detroits id like to put on my car but are slightly different rolling radius. like a 7 revolution difference per mile.
    either way is there a way to determine value of each variant ?im new so go easy
    Byte 3, bits 0~2 in your Instrument Cluster's coding?

    I have no documentation what the eight different "versions" would equate to. But 7 revolutions per mile might be a 1% difference, tops. I think you'll find that none of the tire circumference variants are intended to accommodate such minute changes.

    -Uwe-
    The engineering problems are likely insurmountable. It would be like proposing to land a rocket booster section on a barge floating in the middle of the ocean.

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    Quote Originally Posted by Uwe View Post
    Byte 3, bits 0~2 in your Instrument Cluster's coding?

    I have no documentation what the eight different "versions" would equate to. But 7 revolutions per mile might be a 1% difference, tops. I think you'll find that none of the tire circumference variants are intended to accommodate such minute changes.

    -Uwe-
    so those wouldnt be to adapt different sizes of tires on different models?

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    Benevolent Dictator Uwe's Avatar
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    Quote Originally Posted by dillenger1 View Post
    so those wouldnt be to adapt different sizes of tires on different models?
    Yeah, they may very well be. But they would generally be set up to accommodate more substantial changes than you're making here. For example, Tiguan or Atlas-sized tires.

    -Uwe-
    The engineering problems are likely insurmountable. It would be like proposing to land a rocket booster section on a barge floating in the middle of the ocean.

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    the detroits are from a mk6 GTI .you would think one of those variants is for exactly that tire size.flash file configuration may change variants to different size chassis.IDK

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    Verified VCDS User PetrolDave's Avatar
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    Given that the speedometer is setup to over read by around 5-7% and the number or revolutions per mile is well over 1000 the effect of a difference of 7 revolutions per mile on accuracy of speed and distance is insignificant. Especially if you take into account the variation between a brand new set of tyre and an old set of tyres...

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    Quote Originally Posted by PetrolDave View Post
    Given that the speedometer is setup to over read by around 5-7% and the number or revolutions per mile is well over 1000 the effect of a difference of 7 revolutions per mile on accuracy of speed and distance is insignificant. Especially if you take into account the variation between a brand new set of tyre and an old set of tyres...
    16" stock tire is 811 revs per mile.GTI detroit 18" does 804.isnt there a calibration procedure for the odometer?

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    Quote Originally Posted by dillenger1 View Post
    16" stock tire is 811 revs per mile.GTI detroit 18" does 804.isnt there a calibration procedure for the odometer?
    No, there isn't.

    -Uwe-
    The engineering problems are likely insurmountable. It would be like proposing to land a rocket booster section on a barge floating in the middle of the ocean.

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    ok..so my mk7 ,under tire menu , my display only shows" winter tires" with the speed alarm .
    shouldnt I have another option for "summer"?and is this a different set of variants when cycled between the two?

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    Verified VCDS User PetrolDave's Avatar
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    Quote Originally Posted by dillenger1 View Post
    ok..so my mk7 ,under tire menu , my display only shows" winter tires" with the speed alarm .
    shouldnt I have another option for "summer"?and is this a different set of variants when cycled between the two?
    Nope, the Winter Tires option is only there so you can set a speed warning when winter tires (which normally have a lower speed rating) are fitted - it makes no changes to the odometer or speedometer calibration.

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