Brakes Wheels 2nd Gen Tires Larger Contact Patch for Tire Selection (17in)

Discussion in '2nd Generation: 2007+ R55 through R61' started by bluefox280, May 11, 2012.

  1. bluefox280

    bluefox280 New Member

    May 9, 2012
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    Who's running larger than a 225-series tire on their 2nd-Gen on 17in wheels?
    Like a 235/40-R17 or similar? If so, would love to see / rear the specs (wheel offset & width) and tire manufacturer.

    - Erik
     
  2. Nathan

    Nathan Founder

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    Contact patch area remains the same no matter the size of the tire. What changes is the shape of the contact patch.

    A narrow width will have a contact patch such as...

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    While a wide tire will have a contact patch that encompasses the same area but shaped more like...

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  3. Metalman

    Metalman Well-Known Member
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    In the above example, since the weight didn't change, the #/in. squared stayed the same, the contact patch area didn't change.

    Soooooo, continuing on this same thought....
    If no other changes are made except removing a whole bunch of weight, like seats, interior trim etc.... getting down to race weight..... The contact patch would be reduced, because the weight was reduced. And as long as you don't break tire adhesion..... do both vehicles have the same cornering speed on a track?
     
  4. minimark

    minimark Well-Known Member

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    Sorry Nathan but if both tires have the same diameter and air pressure, I don't see how your contact patches would be correct? The wider the tire the larger the contact patch would be by width, neither widening nor narrowing would effect the patch front to rear..... Please correct me if I am wrong.
     
  5. Nathan

    Nathan Founder

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    From Tire Rack....

    "The shape of a tire's contact patch greatly influences its performance and is dependent on the profile, or "aspect ratio" of the tire. Low profile tires (most performance tires) have a short and wide contact patch that is more effective in converting driver inputs into very responsive handling, cornering stability and traction, especially on dry roads.

    "High profile tires (trucks, most passenger tires) have a long and narrow contact patch that provides more predictable handling, smoother ride and gives better wet weather and snow traction."
     
  6. minimark

    minimark Well-Known Member

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    ...and they are referencing diameter. A wider and larger diameter tire would have more contact patch too. The width of two tires with the same diameter would effect the size of the contact patch.
     
  7. Nathan

    Nathan Founder

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    Given 2 tires with the same diameter such as in a Plus One application the tire with the greater width will have a contact patch that is shorter and wider then the OEM spec narrower section width tire.

    A visual example

    [​IMG]

    Granted, the example pictured above and my other ASCii version are much greater than actual but are that way to prove the point.
     
  8. grodenglaive

    grodenglaive New Member

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    True, but if you reduce the weight you can also lower the tire pressure to retain the same contact patch. :ihih:
     
  9. minimark

    minimark Well-Known Member

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    That represents a lot of deflection... Wonder why racing bicycle tires are so narrow? Less rolling resistance due to a small contact patch?
     
  10. Jason Montague

    Jason Montague New Member
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    :cornut::lol::cornut: Now I remember why I quit arguing with Nathan.:lol::lol::Thumbsup:

    Jason
     
  11. goaljnky

    goaljnky New Member

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    Unscientific opinion:

    For our purposes, you want the short and wide contact patch as that would work better with the lateral forces the tire experiences in the "twisties".
     
  12. Jason Montague

    Jason Montague New Member
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    :cornut::devil::ihih: ...........and avoiding the beer bottles flying out of the Fiat Abarth 500 which is in front of you, going too slow, and won't let you pass!:lol::lol::lol::lol::lol::Thumbsup:

    Jason
     
  13. grodenglaive

    grodenglaive New Member

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    darn beer swilling fiat drivers
     
  14. goaljnky

    goaljnky New Member

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    I am confused. What do you mean "let you pass"? :eek:ut:
     
  15. BlimeyCabrio

    BlimeyCabrio Oscar Goldman of MINIs
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    A really interesting (but long) read, with actual tests and measurements on the relationship of tire size, load, pressures, etc.

    All in a static environment - things change with cornering dynamics - but still very interesting... and completely destroyed some of my long-held beliefs about this topic.

    Fact or Fiction? Tire contact patch and air pressure.
     
  16. minimark

    minimark Well-Known Member

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    Exactly, suffice it to say that there are many variables that effect the size of a tires contact patch. One cannot throw one simple blanket ratio over it... Many things to consider, yes there is. 2cents
     
  17. Firebro17

    Firebro17 Dazed, but not Confused
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    Take the skinny contact patch racing and I'm a believer that one will opt for the fatter contact patch instead... Just my .02. :beer
     
  18. WolfGTI

    WolfGTI Active Member

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    When I am up for tires again I am going from my 215 / 45 / 17's to 245 /40 /17's...wider is better.
     
  19. Dave.0

    Dave.0 Helix & RMW Powered
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    That is exactly what I tell my Dr. when I go in for a check up and get on the scale. Wider is better.


    Lololl:ihih::lol::lol::lol::Thumbsup:
     
  20. BlimeyCabrio

    BlimeyCabrio Oscar Goldman of MINIs
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    You and me both, my brother.
     

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