Results 1 to 3 of 3

Thread: Why do tires have to match?

  1. #1
    Registered User BLITZEN's Avatar
    Join Date
    Jul 2007
    Ski Utah!

    Question Why do tires have to match?

    Iíve been told that itís important for the tires on our cars to match due to the Quattro system. But I donít understand this Ďcause my thinking is that if the right side tire has a worn tread or something causing a difference in overall wheel diameter from the left, wouldnít that be fine? It would just be like a long right hand or left handed turn. Right? So anyone who can explain why or why not tires have to match, please weigh in. Thanks!

    If you never exceed the limits, how do you know where they are?

  2. #2
    Registered User mrdave's Avatar
    Join Date
    Feb 2012
    You have 3 differentials: a front, rear, and a fancy center Torsen diff. My understanding is that any difference in tire diameter puts undue stress on the center diff - the greater the difference, the greater the stress. I believe spec is only a 2-3mm tire diameter difference allowed.

    Diagram for an A4, but same idea: https://drivebywirecf.files.wordpres..._operation.jpg

  3. #3
    Registered User hahnmgh63's Avatar
    Join Date
    Feb 2007
    Roy, WA
    You spend a lot of time going straight than in a turn but you've got the right idea. The engineers designed in enough longevity and as always a buffer when designing diffs to wear a normal life. When you put different size tires on they have to compensate 100% of the time. They'll probably last for years just fine but will see increased wear.
    Same goes for different rolling diameter tires front to rear, then the center differential wear increases. Like I said, probably last for years with no problems but there will be increased wear that is why the engineers specify the tires to be the same and within 3/32". Other manufacturers are around that ballpark.
    2003 White RS6 2013 Midnight Blue S5
    2013 Daytona RS5 2x944 Turbo's 1974 911 w/'91 3.6ltr motor
    Roy, WA

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts