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  1. #1
    GTP Level Member buck531's Avatar
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    Default Tire size tuning

    Does anyone know what the pulses per mile would be going from a tire size of 225/60/16 to a 205/55/16? The MPH reads 5 mph faster than the odometer/pcm reads. I know where to change it, just don't know what to change it to.

    I'm using a DHP too.. in a fiero 3800 swap.
    03 GS - BTTK Intercooler, 3.0 PRJ, 42 lb, SSAC, AEM wb, PT,SR rockers, Gen V, N* TB, dynotech trans w/ 3.29's.

    87 Fiero GT. L67 Swap. XP, ported heads/sc. N* TB. 275 whp on a 3.4 and 8 lbs of boost.

  2. #2
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    Default Re: Tire size tuning

    Why would you go to that tiny a tire?

  3. #3
    GTP Level Member buck531's Avatar
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    Default Re: Tire size tuning

    Because the stock tires/wheels were junk so I found a set of cavalier z24 wheels with 205 tires on them for super cheap. They work. They actually hook but the speedo if off due to the size change.

    I JUST got a set of Beretta 16x7's and planning on 245/50/16 in the back and 225/50/16 in the front.... after I refinish them.
    03 GS - BTTK Intercooler, 3.0 PRJ, 42 lb, SSAC, AEM wb, PT,SR rockers, Gen V, N* TB, dynotech trans w/ 3.29's.

    87 Fiero GT. L67 Swap. XP, ported heads/sc. N* TB. 275 whp on a 3.4 and 8 lbs of boost.

  4. #4
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    Default Re: Tire size tuning

    The circumference of a 205/60-16 tire is 80.69". 785.21 revolutions per mile.,
    The circumference of a 225/60-16 tire is 83.66". 757.35 revolutions per mile.
    A difference of 2.97" or 3.7%
    There are 63,360" in a mile.
    We would need to know how many pulses there are per revolution of the tire.
    https://www.tacomaworld.com/tirecalc...0r16-205-60r16
    2007 Grand Prix GT...bone stock

  5. #5
    GTP Level Member buck531's Avatar
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    Default Re: Tire size tuning

    I'd have to have someone look up the bin file and I'm at work and don't have my tuning laptop with me. Maybe someone (Scotty) can post the stock number. I think it's 23XXX or something around there.
    03 GS - BTTK Intercooler, 3.0 PRJ, 42 lb, SSAC, AEM wb, PT,SR rockers, Gen V, N* TB, dynotech trans w/ 3.29's.

    87 Fiero GT. L67 Swap. XP, ported heads/sc. N* TB. 275 whp on a 3.4 and 8 lbs of boost.

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