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Different Profile Tires

Discussion in 'Tyres & Alloys' started by Ganges, Dec 12, 2012.

  1. Ganges

    Ganges Esperto

    Messages:
    3,121
    Driver Seat _/
    :
    Grande Punto 1.3
    And yes, where are the pics?????

    IMG_20121222_094711.jpg

    - - - Merged Post - - -

    long shot side view

    IMG_20121222_123507.jpg

    - - - Merged Post - - -

    after changing the tire profiles from 195/60 to 195/65 R15 didnt found any difference in the ride and handling done 600 Kms of drive till now with new profile.

    One question,how are our ODO reading callibrated ?

    when the profile was 195/60

    @4th gear at 2000 RPM shows 60Kmph
    @5th gear at 2000 RPM shows 80Kmph

    these remains the same for the profile 195/65 as well :confused: any idea about this ?
  2. sandy.chegi

    sandy.chegi Novizio

    Messages:
    49
    Bangalore
    Hi Ganges, those look gorgeous. For knowing the difference in error, you may refer to the following link:

    Tire Size Calculator

    Enter the OEM profile details. It will show right upgrade and also the % error in readings. Hope the links helps.
  3. Ganges

    Ganges Esperto

    Messages:
    3,121
    Driver Seat _/
    :
    Grande Punto 1.3
    sandy,
    thanks for that,but i have changed only front two tires and i dont know how the ODO reads,i mean the reference points either from Front wheel or rear wheel ? because for me with both the profiles ODO shows the same when seen RPM with speed.
  4. Linear

    Linear Amatore

    Messages:
    236
    Thane
    It will show the same speed. The speedo calculates your speed from the engine rpm & the gear ratio - not from your actual speed. Having different profile tyres does not change anything in the rpm as well as the gear ratio - what it changes is your actual speed.
    2 people like this.
  5. Ganges

    Ganges Esperto

    Messages:
    3,121
    Driver Seat _/
    :
    Grande Punto 1.3
    Linear,
    Thanks for the techie info , you got my point.
  6. vivekrj.dieselhead

    vivekrj.dieselhead Regolare

    Messages:
    294
    delhi
    Well its new to me as well, thanks for the info.
  7. gurjinder

    gurjinder Staff Member Janitor

    Messages:
    3,989
    Punjab
    No, not really.

    Changes in tire size effectively alter the final gear ratio , thereby affecting the calibration of the speedometer. It will be a few % off from the stock tire size.

    Cheers.
    2 people like this.
  8. Ganges

    Ganges Esperto

    Messages:
    3,121
    Driver Seat _/
    :
    Grande Punto 1.3
    gurjinder
    what kind off change should i expect in the drive when gear ratio is altered ?
    i mean more sluggishness or more peppier(im expecting more from change of tirea :D )
  9. gurjinder

    gurjinder Staff Member Janitor

    Messages:
    3,989
    Punjab
    Imperceptible. You wouldn't feel a thing. :)
    1 person likes this.
  10. Linear

    Linear Amatore

    Messages:
    236
    Thane
    I don't see how that can happen. The grears & their teeth are fixed - no change in the gear ratios. What will however change is the tangential velocity at the tread of the tyre. Since the diameter is now slightly more, tangential velocity is now proportionately higher - this will result in slightly higher actual speed than what the speedo indicates.

    It's all pretty inconsequential in practical terms though. I have always noticed that the speedo errs on the plus side, i.e. if your speedo is showing 100 kmph, your car will be actually doing anywhere between 90-97 kmph depending on the speedo accuracy & tyre life. So if you put a slightly higher profile tyre, the most that can happen is that your speedo will be more accurate. Enjoy!
    1 person likes this.

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