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Tyre sizes and 4wd problem

  • 02-07-2010 1:26pm
    #1
    Henry Ford III
    Moderators, Business & Finance Moderators Posts: 17,861 Mod ✭✭✭✭


    Posting for a pal so please be gentle :D

    He has a 2005 Pajero and needed some new front tyres some time back. Tyre place fitted 225 width instead of 255 (original equipped).

    All was well in 2wd but when 4wd was used (during snow last winter) the jeep became very "jerky" when moving away from a stop.

    Could the narrower tyres have caused transmission damage? :confused:


Comments

  • #2
    CJhaughey
    Registered Users, Registered Users 2 Posts: 14,907 ✭✭✭✭CJhaughey


    Henry Ford III wrote: »
    Posting for a pal so please be gentle :D

    He has a 2005 Pajero and needed some new front tyres some time back. Tyre place fitted 225 width instead of 255 (original equipped).

    All was well in 2wd but when 4wd was used (during snow last winter) the jeep became very "jerky" when moving away from a stop.

    Could the narrower tyres have caused transmission damage? :confused:
    Was the tyre diameter the same? If the 225 were the right aspect ratio so as to make them the same diameter as the 255s then there shouldn't be a problem. IF the 225 were of a different diameter the the rear 255 tyres then the resulting difference may have induced transmission windup.
    Hence the jerky behaviour.


  • #3
    Henry Ford III
    Moderators, Business & Finance Moderators Posts: 17,861 Mod ✭✭✭✭Henry Ford III


    CJhaughey wrote: »
    Was the tyre diameter the same? If the 225 were the right aspect ratio so as to make them the same diameter as the 255s then there shouldn't be a problem. IF the 225 were of a different diameter the the rear 255 tyres then the resulting difference may have induced transmission windup.
    Hence the jerky behaviour.

    Tyres were identical bar the tread width CJh. Same profile rating etc. Just 30mm narrower on the front axle only.

    Thanks for your reply.


  • #4
    CJhaughey
    Registered Users, Registered Users 2 Posts: 14,907 ✭✭✭✭CJhaughey


    Henry Ford III wrote: »
    Tyres were identical bar the tread width CJh. Same profile rating etc. Just 30mm narrower on the front axle only.

    Thanks for your reply.
    That means the tyres were different diameters if they had identical profile rating and different widths.


  • #5
    peasant
    Registered Users, Registered Users 2 Posts: 17,819 ✭✭✭✭peasant


    CJhaughey wrote: »
    That means the tyres were different diameters if they had identical profile rating and different widths.
    and thats because the second figure in the tyre size is a percentage of the width and not an absolute dimension

    eg. 215/70/15 = 215 mm wide / 70% of 215 mm flank height / 15 inch inner diameter

    The tyre "expert" that fitted those different tyres deserves to be shot


  • #6
    CJhaughey
    Registered Users, Registered Users 2 Posts: 14,907 ✭✭✭✭CJhaughey


    peasant wrote: »
    and thats because the second figure in the tyre size is a percentage of the width and not an absolute dimension

    eg. 215/70/15 = 215 mm wide / 70% of 215 mm flank height / 15 inch inner diameter

    The tyre "expert" that fitted those different tyres deserves to be shot
    Correct, never trust a rubbermonkey.


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  • #7
    Henry Ford III
    Moderators, Business & Finance Moderators Posts: 17,861 Mod ✭✭✭✭Henry Ford III


    Understood. Could this error have messed up the tranny though?

    If so how is it fixed?


  • #8
    Rovi
    Closed Accounts Posts: 8,570 ✭✭✭Rovi


    Henry Ford III wrote: »
    Understood. Could this error have messed up the tranny though?
    Possibly, but unless it was driven in 4WD on good grippy surfaces for a long time, it's unlikely.
    Henry Ford III wrote: »
    If so how is it fixed?
    The very first thing to do is to fit the correct tyres and see if the symptoms disappear.


  • #9
    Henry Ford III
    Moderators, Business & Finance Moderators Posts: 17,861 Mod ✭✭✭✭Henry Ford III


    Thanks all. Inputs much appreciated.

    Tyres are being changed as we speak to original spec. all round. I'll report any progress.


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