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Mixing tyre sizes

  • 30-09-2019 8:36am
    #1
    mp3ireland2
    Registered Users, Registered Users 2 Posts: 1,876 ✭✭✭


    Hi,
    I've currently got 215/50r17 tyres on my ford focus. Could I put 205/50r17 tyres on the back, leaving the larger ones on front (these are the original size that came with car). Even with the slightly larger tyres on front the Speedo is still reading well below the true speed per GPS. Just checking if any safety or legal issues doing this, tyres on each axel will match.


Comments

  • #2
    kaahooters
    Registered Users, Registered Users 2 Posts: 720 ✭✭✭kaahooters


    Why?


  • #3
    mp3ireland2
    Registered Users, Registered Users 2 Posts: 1,876 ✭✭✭mp3ireland2


    I have two tyres with about 7mm thread that came with the car. I just bought 2nd hand wheels with tyres when i bought the car from a focus mk3 which have the slightly larger tyres. I put new tyres on the front recently but wondering for the rear could i use the smaller 205 tyres or would there be issues. So just to use the tyres I have available really, easier on pocket and better not to waste them.


  • #4
    mickuhaha
    Registered Users, Registered Users 2 Posts: 475 ✭✭mickuhaha


    So long as tyres and rims are matched on same axle you are good to go. Just don't go too far bigger or small on the extreme.


  • #5
    Andrewf20
    Registered Users, Registered Users 2 Posts: 3,254 ✭✭✭Andrewf20


    Shouldnt be an issue. Id say go for it.


  • #6
    standardg60
    Registered Users, Registered Users 2 Posts: 5,336 ✭✭✭standardg60


    According to wheelfitment.eu (which i find very useful), only 215s are specified for the mark4 and only 205s are specified for the mark3, so the 205s may not seat correctly on the mark4 rims if thats what you were planning on doing.


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  • #7
    kirving
    Registered Users, Registered Users 2 Posts: 6,236 ✭✭✭kirving


    Should be fine. They're not particularly low profile, so should seat fine on the same rims.

    New ones are 215mm wide, 5mm wider per side than the others.

    But they have a height of approx 107.5mm (215*50%). This means that due to the height of the sidewall, the angle that the sidewall will sit at is pretty small relative to before.

    For comparison, the tyres on my car (in which I assume has identical rims all around) are 265/35R18 and 245/40R18 as per manufacturer's spec. ie: a 20mm difference from front to rear. The sidewall height is also 5mm different since the 35% of 265mm does not match 40% of 245mm.

    As far as I know anyway, all of these sizes are not actually exact, but more so a convention for differentiating between sizes using meaningful figures. In reality, there will be slight differences between manufacturers.


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