Tyre Profiles

Discussion in 'Wheels, Tyres, Brakes & Suspension' started by terrymcg, Jul 10, 2011.

  1. terrymcg

    terrymcg Active Member

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    Does anyone know what the harm or detremental effects would be in fitting a 225/35/18 tyre to the front of the car rather than a 225/40/18? I take it that the speedo is slightly/badly knocked out?? Anything else?
     
  2. Stratman

    Stratman MB Enthusiast

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    The cruise control will probably drop out at higher speeds.
     
  3. renault12ts

    renault12ts MB Club Veteran

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    The diameter of your tyre will be nearly an inch greater. Why do you want to do this?
     
  4. mazza

    mazza Active Member

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    225/40/18
    Rolling Radius: 200.18 cm
    Total Diameter: 63.72 cm
    Sidewall Height:9.00 cm

    225/35/18
    Rolling Radius: 193.11 cm
    Total Diameter: 61.47 cm
    Sidewall Height:7.88 cm

    actual speed will be less by 3.5% compared to indicated speed

    you will be loosing tyre sidewall height...so ride will be slightly harder...but probably grippier in corners (ensure pressures are spot on).

    thats about it really

    mazza
     
  5. whitenemesis

    whitenemesis MB Club Veteran

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    Possibly unbalance the handling slightly by changing the relative stiffness front to rear?
     
  6. crockers

    crockers MB Enthusiast

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    If you speedo is on the limit of it's 10% accuracy would the car still be legal?
     
  7. whitenemesis

    whitenemesis MB Club Veteran

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    Speedo will be over-reading (i.e. fast) so potentially saving you from speeding?
     
  8. rf065

    rf065 MB Enthusiast

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    Lot of assumptions here, but you are talking about changeing the front tyres only? Do you already have a staggered wheel set up? If you do there may already be a discrepency between front & rear tyres that will be exagerated if you change the fronts.

    Russ
     
  9. whitenemesis

    whitenemesis MB Club Veteran

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    IIRC MB introduced the staggered setup specifically to create the difference in stiffness. This provides a safe handling characteristic without undue change in ride.
     
  10. OP
    OP
    terrymcg

    terrymcg Active Member

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    Yes I already have a staggered set up, 255/35 on the rear and 225/40 on the front. i just dont like the look of the 40's on the front - they look like tractor tyres compared to the rear in my opinion.

    Just wondered if there would be any harsh side affects of sticking a 35 on the front - obviously it will still be staggered just a different profile. So a harder front end.
     
  11. rf065

    rf065 MB Enthusiast

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    As standard the discrepancy between front & rear is only 0.2%

    Specification Sidewall Radius Diameter Circumference Revs/Mile Difference 225/40-18 3.5in 12.5in 25.1in 78.8in 804 0.0% 255/35-18 3.5in 12.5in 25.0in 78.6in 806 -0.2%

    Changeing the fronts to a 225/35 will alter this to 3.4%, possibly more than the electronic safety systems would like, you would need to try it first to be sure, Expensive exercise if it does not work though.

    Russ
     
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