Results 1 to 9 of 9

Thread: VSS Tire Revs per mile confusion.

  1. #1
    Tuner in Training
    Join Date
    Dec 2018
    Posts
    30

    VSS Tire Revs per mile confusion.

    Hi I been having a little issue trying to get my car to shift to where I set it in my 04 mustang gt with 3.73 gears,
    Shift scheduling and gear is correct so I looked at tire settings. I have 245/45/R17 Firestone Indy 500s
    55555555.png

    I looked up quite a few charts couple said that is accurate at 812 RPM.
    but couple others plus doing math manually says 784.7 RPM

    Anyone got any Input?

  2. #2
    Advanced Tuner
    Join Date
    Mar 2010
    Location
    New Orleans, LA
    Posts
    628
    you have use VID enabled

    you need to disable vid and use the cal values otherwise anything you set it to will not be used

  3. #3
    Tuner in Training
    Join Date
    Dec 2018
    Posts
    30
    Yes It is disabled in the tune I took a picture of the stock tune where it still showed 812. I'm having issue where I tell it to shift at 41mph@5800rpm but its shifting at 35mph@5000 gear ratios and shift scheduling is accurate

    For 245/45/r17s what would the TRPM be? I'm getting mixed answers in my research.

  4. #4
    Advanced Tuner
    Join Date
    Mar 2010
    Location
    New Orleans, LA
    Posts
    628
    shift schedule mph is from nvbase

    you need to set it correctly

    tire revs * rear end gear ratio / 60

  5. #5
    Tuner in Training
    Join Date
    Dec 2018
    Posts
    30
    Idk how else I can state it. My shift scheduling and gear ratio is set correctly this I'm certain. Speedometer is slightly off because of the TRPM is off. I'm trying to find out the right value for it. Half charts I've found say one thing other half say another. The math even shows another number.

  6. #6
    Advanced Tuner
    Join Date
    Jun 2008
    Location
    Tyler/Longview, TX area
    Posts
    746
    The info I found said 812. You can measure rollout to be sure of the number. You said your car is 04?

  7. #7
    Advanced Tuner
    Join Date
    Mar 2018
    Posts
    447
    Yep, measure the roll out for one rev of the tire. Then do some math.

    If it rolls out 12 inches it will translate to 5280 revs per mile.

    I used one foot because I'm lazy.

  8. #8
    Tuner in Training
    Join Date
    Dec 2018
    Posts
    30
    yea its a 04. 812 was factory number so maybe thinking maybe it had another tiresize stock. I was using Diameter. Now I gotta figure out why Its shifting early. Its set to shift 60%-100% throttle at 41mph@5800rpm to second its shifting 35mph at 5000rpm WOT

  9. #9
    can you post a log? you might be hitting a torque limit or something making it shift faster than you want.

    Try to log torque source, or anything with source in it, anything with limit in it.