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Tyre size question

  • 25-09-2012 10:53am
    #1
    Seanieke
    Registered Users, Registered Users 2 Posts: 853 ✭✭✭


    Hey all,

    I'm hoping someone here can sort this out for me,

    I'm after a new set of tyres for the van, it's a Caddy with 195/65/15's on it, the tyre I want is a UniRoyal Rainmax2, the problem is they only come in 195/70/15...

    Now on any given day you'll see Caddy vans with all sorts of alloy wheels on them, usually 18's and the like so I'm presuming the extra "5" on my new wheels wouldn't make much of a difference?

    Figure I'm better asking before hitting buy on EireTyres!

    Thanks


Comments

  • #2
    beazee
    Registered Users, Registered Users 2 Posts: 1,343 ✭✭✭beazee


    65% of 195mm wide = 126.75mm height (ca. 5 in)

    70% of 195mm wide = 136.5mm height (ca. 5.4 in)

    Is 0.4 inch a difference to you?


  • #3
    Nissan doctor
    Closed Accounts Posts: 8,223 ✭✭✭Nissan doctor


    Seanieke wrote: »
    Hey all,

    I'm hoping someone here can sort this out for me,

    I'm after a new set of tyres for the van, it's a Caddy with 195/65/15's on it, the tyre I want is a UniRoyal Rainmax2, the problem is they only come in 195/70/15...

    Now on any given day you'll see Caddy vans with all sorts of alloy wheels on them, usually 18's and the like so I'm presuming the extra "5" on my new wheels wouldn't make much of a difference?

    Figure I'm better asking before hitting buy on EireTyres!

    Thanks


    Are the Uniroyals the correct speed/load rating for your van?


  • #4
    Esel
    Registered Users, Registered Users 2 Posts: 23,589 ✭✭✭✭Esel
    Not Your Ornery Onager


    beazee wrote: »
    65% of 195mm wide = 126.75mm height (ca. 5 in)

    70% of 195mm wide = 136.5mm height (ca. 5.4 in)

    Is 0.4 inch a difference to you?
    Wouldn't that be 0.8" (twice the height difference)?

    Not your ornery onager



  • #5
    coylemj
    Registered Users, Registered Users 2 Posts: 25,702 ✭✭✭✭coylemj


    Esel wrote: »
    Wouldn't that be 0.8" (twice the height difference)?

    You're correct, the overall diameter of the tyre will be 0.8" (actually 0.77") greater. However for clearance (space between the tyre and wheel arch) purposes it's the radius difference that matters and that is 0.38".


  • #6
    beazee
    Registered Users, Registered Users 2 Posts: 1,343 ✭✭✭beazee


    0.4" is our concern for an arch clearance. 0.8" would be overall height difference.


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  • #7
    Esel
    Registered Users, Registered Users 2 Posts: 23,589 ✭✭✭✭Esel
    Not Your Ornery Onager


    There is also the issue of circumference, which could affect the speedometer reading.

    Not your ornery onager



  • #8
    coylemj
    Registered Users, Registered Users 2 Posts: 25,702 ✭✭✭✭coylemj


    Esel wrote: »
    There is also the issue of circumference, which could affect the speedometer reading.

    +1 Speedo will understate by 3%. The circumference of the existing tyres is 1,993 mm, the proposed replacements will be 2,055 mm.


  • #9
    beazee
    Registered Users, Registered Users 2 Posts: 1,343 ✭✭✭beazee


    At 100kph speedo he will actually be doing 103.16kph
    http://www.alloywheels.com/Tyre_Calculator


  • #10
    Seanieke
    Registered Users, Registered Users 2 Posts: 853 ✭✭✭Seanieke


    Nissan doctor wrote: »
    Are the Uniroyals the correct speed/load rating for your van?

    Yeah the RainMax are a Commercial tyre and they're rated for 170KPH, they'll never see that while I'm driving anyway.


  • #11
    Seanieke
    Registered Users, Registered Users 2 Posts: 853 ✭✭✭Seanieke


    beazee wrote: »
    65% of 195mm wide = 126.75mm height (ca. 5 in)

    70% of 195mm wide = 136.5mm height (ca. 5.4 in)

    Is 0.4 inch a difference to you?

    That's not going to make much of a difference at all to me, more rubber all around means the rim's less likely to get buckled as far as I'm concerned!


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  • #12
    Seanieke
    Registered Users, Registered Users 2 Posts: 853 ✭✭✭Seanieke


    beazee wrote: »
    0.4" is our concern for an arch clearance. 0.8" would be overall height difference.


    Would the height difference still not only be 0.4" because the van can only sit on one side of the tyre at a time?


  • #13
    coylemj
    Registered Users, Registered Users 2 Posts: 25,702 ✭✭✭✭coylemj


    Seanieke wrote: »
    Would the height difference still not only be 0.4" because the van can only sit on one side of the tyre at a time?

    Correct, the axles will be 0.38" higher off the ground so that will be the increase in overall height of the vehicle and the reduction in clearance above the tyres will be the same


  • #14
    Seanieke
    Registered Users, Registered Users 2 Posts: 853 ✭✭✭Seanieke


    coylemj wrote: »
    Correct, the axles will be 0.38" higher off the ground so that will be the increase in overall height of the vehicle and the reduction in clearance above the tyres will be the same

    Well with the arch clearance on the Caddy I could prob fit a spare tyre between the tyre and arch so it'll do grand!


  • #15
    Nissan doctor
    Closed Accounts Posts: 8,223 ✭✭✭Nissan doctor


    Seanieke wrote: »
    Yeah the RainMax are a Commercial tyre and they're rated for 170KPH, they'll never see that while I'm driving anyway.


    There are numerous different load ratings for commercial tyres so you'll need to be sure that they are the same load rating as the factory rating for your van or you will likely end up with issues come DOE time.

    Also, 195/70/15 is a size not used on modern car/van type vehicles so you'd need to make sure they are designed for a van like the new model caddy(i.e basically car tyres with a higher load rating) as opposed van tyres for the likes of a hi-ace(which uses 195/70/15s) that would not be suited to a caddy at all.


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