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Is there a way to correct speedometer after bigger tires

Discussion in '100-Series Cruisers' started by Nolan Sylvester, Jul 17, 2017.

  1. Nolan Sylvester

    Nolan Sylvester

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    just as the title says. I searched, albeit, briefly and didn't have luck. Can you adjust the speedometer after you go bigger on tires?
     
  2. TheForger

    TheForger

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  3. planomateo

    planomateo

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  4. LX470Beast

    LX470Beast

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    On my 2004 LX470, I used the nav screen or the screen under settings. There is a button you could push to calibrate with new/bigger tires. I have 38x15.5 and my speedometer is dead on. No additional install or cost.
     
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  5. hoser

    hoser SILVER Star

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    ^^^^I don't have the stock Navi but I was under the impression the Navi tire settings was only for dead reckoning for Navi purposes, like going into a tunnel or garage. You're saying it corrects the speedometer needle and odometer on your instrument cluster?

    Are you not running 5.29 gears with your 38's? That would correct your speedometer right there.
     
  6. LX470Beast

    LX470Beast

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    Not sure about my gear ratio, when I got my truck built I know my speedo was off. This was verified my those "this is your speed" checks you see all over. I happened to fish around the system settings on my screen and found it and push it out of curiosity and it worked. Yes the speedometer was corrected, can really verify odometer or I haven't verify it. I would give you screen shoots but I removed my factory nav and those option are no longer available.
     
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  7. jLB

    jLB Curmudgeon in training

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    I've spent the last 11 years with an 06 LX470 and never seen anything like that in the Nav system...

    There is a "set speed", but that is for travel time estimates:
    upload_2017-7-17_14-19-32.png

    ( Whole manual available here http://drivers.lexus.com/t3Portal/document/omnav-s/OM60A28U/pdf/OM60A28U.pdf )

    To the OP, the yellowbox in my son's vehicle has worked wonderfully, once we got it calibrated/adjusted properly.
     
  8. Nolan Sylvester

    Nolan Sylvester

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    The first box in setup is calibration. Click the change on that. It gives you a new tires calibration click that and it says it's calibrating. I have not had an opportunity to get on the interstate but at 45 my speed app says I was going 46. I only knew what my speed was on the interstate so I'll keep you posted
     
  9. planomateo

    planomateo

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    But I don't think calibrating the NAV changes the speed on the speedometer.
     
  10. jLB

    jLB Curmudgeon in training

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    upload_2017-7-17_14-39-31.png
    upload_2017-7-17_14-40-32.png

    I love for it to be that simple, but as stated above, I suspect this is for Nav distance estimation on a weak/missing GPS signal, not (dash) speedometer correction.
     
    Last edited: Jul 17, 2017
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  11. LX470Beast

    LX470Beast

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    It is that simple, if I remember correctly, my speedo was off by 3-5 mph with my 38" and this corrected that. Don't compare gps vs speedo, there is a lag in the gps signal. I see this on my radar detetector a lot. Use the "your speed signs" is based on radar. You could also use another car to try to calibrate. Remember your car is also connected to your speedo, i.e. Your car is always checking how fast your going thus disabling nav functions. This might be connected to nav or speedo or both.
     
  12. jLB

    jLB Curmudgeon in training

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    It's easy enough to test your theory on the drive home, but I am skeptical.

    3-5mph off at what speed? Generally, your speedo would be off by a percentage. Mine is off ~5.1%. For me at least, in town it is pretty much insignificant. At freeway speeds, it may start becoming significant at 85, it's up to ~+4.25mph
     
  13. LX470Beast

    LX470Beast

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    Was off 3-5 between 45-60, the higher the speed the more is off. Remember your speedo is no longer analog it may look analog but it's solely control by a computer. I have pulled my nav in my car, completely removed the nav brain, stereo brain, and amp. As it stand I retained the Lexus nav screen so I can control the AC. Remember these cars ac is controlled by the same screen as the nav but my trip info is still functional on the same screen. This tells me speed and mileage/speed information is independent from the navigation.

    This is what I done with nav and stereo:

    Successfully Moved Navigation Screen To Make Room Pioneer AVIC-8200
     
  14. jLB

    jLB Curmudgeon in training

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    Why is it that I'm hearing Bruce Campbell's voice as Ash (Army of Darkness) directed at me, in the back of my mind as I read the above...

    Ash: Don't touch that please, your primitive intellect wouldn't understand alloys and compositions and things with... molecular structures.


    After hitting the Nav "setup" --> "calibrate" --> "tire change" and traveling ~15mi at speeds from 30-70mph, I am not seeing any difference in speedometer error.

    Yes, I'm pretty familiar with how the speedometer works after chasing it through the EWD to install my son's yellow box. The sensor on the drivetrain sends pulses to the ECU, the speed is determined/calculated by the frequency of the pulses. The typical speedometer adjustment boxes take the original pulses as input, and applies a "multiplier" to generate a modified output signal to correct the error.

    Yes, I've seen the SAS thread, and the MFD relocation threads for your vehicle.

    Yes, I am aware of the different systems controlled through the MFD.

    So you're explaining that, a screen that you can no longer reach (because of the equipment that you yanked), somehow automagically reprogrammed a the tire size in the ECU, (or some other part that you didn't yank), and strangely enough, this parameter doesn't seem to appear anywhere in Techstream?
     
    Last edited: Jul 17, 2017
  15. Nolan Sylvester

    Nolan Sylvester

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    I don't be think it fixed mine. I will be able to tell for sure tomorrow after I get on the freeway.

    JLB, how hard was it to install and calibrate the yellow box?
     
  16. LX470Beast

    LX470Beast

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    At the end of the day. My speedometer was off after the SAS and tire size increase, it was a concern of mine before the swap. All I did was calibrate the system through the nav/setup. As it stands my speedo is dead on when approaching those radar controlled signs as well as verifying with my wife's car next to me, tested at various speed. Not sure what the deatails are but I have no issues with speedometer. I was skeptical initially but it's been over 2 years and still no issues even with the equipment yanked out. The only thing I could think of is the parameter value is stored some where only a computer is the only thing that could change it, lack of power or other variables cannot effect it. Maybe is similar to the way new computers can keep track of license keys ( once entered you don't have to re-enter even if you change hdd or reinstall Windows. As a preventive for piracy.). I'm not saying I'm right or wrong but it worked for me. Last time I checked there not many LX470 running 38 x15.5 and to have no issues with speedometer is even better.
     
  17. jLB

    jLB Curmudgeon in training

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    The yellowbox is pretty easy to install, there are 2 basic ways to install it:

    1) Buy the prebuilt harness and insert it inline at the VSS.
    2) Splice into the VSS output from the ECU to the gauge cluster​

    On my son's truck I chose option 2.

    I have a yellowbox for my LX, that's been sitting in a drawer for 2 years. I just haven't felt a real need to install it. I'm running 285/65R18 tires and I know how far it's off ~1.7mph at 35mph ~3.5mph at 70mph. If I do install it, I will probably go with option 1.

    If your comfortable under the truck and don't mind either weatherproofing the box, or routing a cable inside, option #1 is no big deal. (Easy connection, minor PITA routing cable, everything receives the updated signal)

    If you're comfortable reading the EWD, soldering and shrink wrapping the connection option #2 is no big deal. Routing the cable into the glovebox is pretty much a done deal. (Minor PITA connection, easy cable routing, only gauge cluster receives a modified signal)

    It does take a little time get the hang of how to make adjustments, but if you read the instructions, it's all right there.

    Yellowbox Speedometer Correction Install
    DIY: Marks Speedo Correction Install 2004 100 Series
    Speedo Correction for the 100
    Speedo doesn't need correction
     
    Last edited: Jul 17, 2017
  18. LandCruiserPhil

    LandCruiserPhil Peter Pan Syndrome Supporting Vendor

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    If the 100 is anything like 80 there are more than 1 VSS. On an 80 series the VSS for the gauge cluster does not talk to the ECU for it has its own VSS.
     
  19. jLB

    jLB Curmudgeon in training

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    I have no doubt that your speedo is working, but as someone with an engineering background that has spent more than 1/2 their life working in IT, I have great difficulty with "it's just computer magic".

    Out of curiousity, what gear ratio are you running in the 80 series axles under your LX470?
     
  20. jLB

    jLB Curmudgeon in training

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    I do remember that there is a VSS1 and a VSS2 at some point in the EWD, but I was primarily interested in the branch to the instrument cluster, and not the one for transmission data. Please don't make me trace the line(s) through the EWD again, they make my head hurt.