18 & 19" on the same car?

Discussion in 'Wheels and Tyres' started by bmwzoom, Jan 15, 2020.

  1. bmwzoom
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    bmwzoom

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    So based on the below would it be possible in an emergency to run 18" & 19" wheels on the same car? I have staggered setup hence the question

    You must always make sure that tyres on the same axle are of the same size and aspect ratio – your car will fail the MOT test if they’re not.

    Thanks
     
  2. snrbrtsn
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    snrbrtsn WARLORD Site Supporter

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    Hi Pete
    As per question, in a emergency it’s allowed hence spare wheel sizes are seldom of same size
    Whilst I have 20” wheels, I have 19” spare wheel although 18” is available and 17” possible albeit only fit the rears due to Cali per clearance!

    Another take is with consideration to xdrive transfer boxes, as long as the smaller wheel has larger (matched) profile the rolling circumference should / “may” be the same...
     
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  3. bmwzoom
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    The reason was that I have purchased a set of stagger 18's from an F30 for my F34 as a spare set. They will fit no problem as its a standard size but in the event that I have a damaged 19 either front or rear I am presuming that as long as I fit 2 x 18" on the same axle then I should be fine. Tyre size will be the same
     
  4. snrbrtsn
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    snrbrtsn WARLORD Site Supporter

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    Afaik, there’s no need to fit x2
    It’s not as if you’d carry x2 at all times, I’d use a single front as spare to cover all bases
    I’d also check the 18” wheels fit, the blue m sport callipers are bigger
     
  5. bmwzoom
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    I don't think you can due to the transfer box:whistling: my understanding is that they both have to be the same size on the same axle or am I missing something? Hence the reason BMW don't make a space saver for the xdrive cars with staggered setup or any xdrive car
     
  6. bmwzoom
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    18" will fit as its as low as you can go I checked the tyre sizing panel on the door post (y)
     
  7. snrbrtsn
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    I could be entirely wrong though I believe in std trim the car has a square set up and the larger sized wheels (cost option) are staggered to allow for better handling and aesthetics, therefore the same spare wheel is usable!
    The door card will highlight available wheel sizes
     
  8. snrbrtsn
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    snrbrtsn WARLORD Site Supporter

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    The purpose of use is for emergency situations and never intended for long term use
    The restrictions to speed and distance that most spare wheels have is indicative of short term use
    As long as the spigot, stud pattern and profiles are matched all should be well
     
  9. bmwzoom
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    Yes you are perfectly correct but I fail to see that you can run an 18" on the same axle as a 19" tho even if the tyres are the same size.

    I am running:

    Front 225/45/19 8J x19 ET 30
    Rear 255/40/19 9J x 19 ET 42

    18's are:

    Front 225/45/18 8J ET 34
    Rear 255/40/18 81/2 J ET 47

    Profile should be 50 front & 45 rear but will make no differnece

    All runflats

    Square setup is 18's all round 34 ET 8J
     
  10. bmwzoom
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    Ok in which case as my 18's have the same profile as the 19' on the car all should be well although the correct profile for 18's on the door post is 5mm different
     
  11. snrbrtsn
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    Correct!
    Whilst the wheels maybe uniform between F30&F34 the tyres may differ and/or incorrect tyres are fitted?
    My internet is on a go slow....

    Note : I’m not seeing an 81/2” wheel for 3 series (albeit American site)
    https://www.wheel-size.com/size/bmw/3-series/2016/
     
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  13. bmwzoom
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    They came from an F30 320d with staggered setup
     
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    That’s an unusual tyre combination, I think it’s thrown by 8.5” rear wheel

    225/40/18 18x8.5ET35 front
    255/35/18 18x9.5ET35 back ED0D5020-7C87-40A3-8C2A-4F8B3A7BD5D7.jpeg
     
  15. bmwzoom
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    2016 320d

    225/45ZR18
    255/40ZR18
    8Jx18 ET34
    8.5Jx18 ET47
     
  16. bmwzoom
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    Removed from a BMW 3 SERIES F30 320D M SPORT This Alloy Wheels Set V SPOKE 658 REAR 8.5J X 18 ET47 - FRONT 8J X 18 ET34 suits F30 3 Series LCI models from March 2014 only

    The BMW Part Number for this item is 36116866398/36116866306
     
  17. Peter
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    If you intend to run the current tyre sizes on the 18/19" (in the event of a wheel issue) even across axles, then you do have a problem. Definitely outside the xDrive tolerance 'front to rear' whatever combination. You'd need to change the profiles to those you highlight. Even then worth double checking the RC of the mix, to ensure you are within about 1%.

    Peter
     
  18. Mieke
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    Mieke WARLORD Site Supporter

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    On an xDrive I would only do that in an emergency, or it could lead to problems with the transfer box. OK for a limited number of miles. Also, handling would be unpredictable. I find that the response between 18" fitted with winters is markedly different to 19" lower profile P Zero's.
     
  19. bmwzoom
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    Standard square setup below:

    225/45R18 8Jx18 ET34

    Sorry but I fail to see where the slight difference in profile will cause any issues as they match the 19's. Surely profile only governs ride height?? Clearance on other areas is not an issue.
     
  20. Peter
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    For example, I read it you could be running 225/45 R18 with 255/40 R19, if you mix. That translates to a completely different RC, front an rear. A 3.8% difference.

    Peter
     

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