Wheel numbers?

Discussion in 'Wheels, Tyres, Brakes & Suspension' started by Burger, Oct 9, 2011.

  1. Burger

    Burger Active Member

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    Whenever I see people on here talking about wheels, as well as the wheel rim width and diameter they mention another number that appears to be important... ET? I gather, I think, it is the offset of the inner face of the hub mounting... but I'm not sure. Could someone please explain?

    Also, then, when looking at wheels for my car, how can I possibly know what this number needs to be?

    My car is currently fitted with 8.5J x 18 fronts and 9.5J x 18 rears (what does the J stand for?). The car when new would have been standard with 8.5J x 17's all round. If I decided to fit 17 inch wheels for winter, same size all round, what would this third mystical number be? The offset one? Then, knowing that, am I restricted to wheels designed specifically for the SL or would 8.5J x 17 inch wheels from other models be identical?

    Sorry, lot's of questions, but it's an area I find quite mind boggling when you see how many wheels are available and one I don't understand at all.

    Thank you.
     
  2. simonegypt

    simonegypt New Member

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    The Mercedes SL R230 original 17” fitment front & rear should be ET 35. However, on our CLK the wheel is 17x7.5" ET 36 front, 17x8.5" ET 34 rear; while on different 17 7.5” wheels with winter tyres on, the ET is 17. So check with a dealer or wheel supplier to be certain on what to buy. Narrower is better for snow. ET is from the German einpresstiefe,(? Spelling) which means the rim centreline offset from the hub fitting plane of the wheel. The ‘J’ is the shape of the rim where the tyre fits and is a very common designation for ‘normal’ British wheels since I can remember. Members more knowledgeable than I can ascertain whether fitments from other models are suitable. Some Mercedes dealers are doing winter tyre wheel deals. Could be worth asking what is the fitment for your car.
     
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  3. Wilfie

    Wilfie Active Member

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    There's a sticky with various wheel sizes, the offsets and the tyre sizes at the top of this forum. I to was baffled but that helped a lot.
     
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  4. npuk

    npuk MB Enthusiast

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    Alloy wheels, wheels, onformation on wheels, offset, wheel offset, wheel sizes.

    Alloy Wheels Direct Ltd | Fitting Chart Index

    The J stand for joule. All you need to really know is the number with J is the alloy width. Number with ET is the offset.

    As for the changing the wheels to 8.5J x 17 you would look at the fitting chart above and see what the offset should be for that width and size of wheel on your car.

    As for fitting alloys from other models it is possible if the offset of the alloys is correct for your car.
     
    Last edited: Oct 9, 2011
    2 people like this.
  5. OP
    OP
    Burger

    Burger Active Member

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    Thanks to all for the replies.

    I'd seen the sticky at the top but two things struck me about it. Firstly being in a list, while useful, it doesn't make it easy to find if wheels for any other model are suitable for my car. Secondly, all the recent posts on that thread seem to be from people asking questions with no one answering them.

    Thanks to those who took the time to reply to me here, it is much appreciated.

    Regards,
     
  6. Chrishazle

    Chrishazle MB Enthusiast

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  7. BTB 500

    BTB 500 MB Club Veteran

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    There's a really good explanation here:

    Car Bibles : The Wheel and Tyre Bible Page 4 of 4
     
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  8. Wilfie

    Wilfie Active Member

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    Cheers BTB, still trying to work out what MT20 means on my replicas, surely it's the offset!
     
  9. steverupi

    steverupi New Member

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    this site gives you all the cars with wheels that fit your car too.
     
  10. steverupi

    steverupi New Member

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  11. grober

    grober MB Master

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    This actually says it all Trivia note: ET comes from "Einpresstiefe" in German - rim offset (actually "inset", literally). :eek: In other words the vertical plane where the mating face of the axle hub meets the wheel hub and its relationship to the imaginary vertical plane at the exact horizontal centre of the wheel rim. They make great play of the fact a lot of wheel "inset"might mean fouling the suspension components but neglect the other circumstance where a wider rim with the correct offset /ET = "inset" for suspension clearance may start to foul the wheel arch/lip by jutting out too much. :p

    Read more: Car Bibles : The Wheel and Tyre Bible Page 4 of 4
     
    Last edited: Aug 20, 2012
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