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Thread: What does ET mean, aka Offset?

  1. #1
    Administrator footose has a reputation beyond repute footose has a reputation beyond repute footose has a reputation beyond repute footose has a reputation beyond repute footose has a reputation beyond repute footose has a reputation beyond repute footose has a reputation beyond repute footose has a reputation beyond repute footose has a reputation beyond repute footose has a reputation beyond repute footose has a reputation beyond repute footose's Avatar
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    What does ET mean, aka Offset?

    A lot of people don't know this... (and I myself just figured it out)



    For any individual alloy or steel wheel, ET and Offset both have the same meaning and value. The term ET originates from the German word 'Einpresstiefe' which translates as 'insertion depth'.


    A:The distance between the rim's center line and its
    mounting surface. From the picture below it should be
    obvious why it's important to retain proper offset when
    you change rims: tire not centered properly affecting
    drivability (negative roll radius changes), bearing load,
    rubbing on the struts or wheel arches, etc.

    Cross sectional view of a rim:



  2. #2
    Banned MK2TDI is on a distinguished road
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    ive always wondered that myself too, but always been too embarrassed to ask lol...when people are selling wheels and they mention the ET..im like "WTF is that?"... im glad i know this now ...

    thanks alot footose

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    Veteran Member Raz has a reputation beyond repute Raz has a reputation beyond repute Raz has a reputation beyond repute Raz has a reputation beyond repute Raz has a reputation beyond repute Raz has a reputation beyond repute Raz has a reputation beyond repute Raz has a reputation beyond repute Raz has a reputation beyond repute Raz has a reputation beyond repute Raz has a reputation beyond repute
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    Good info post! I've got a fair understanding of how it works and what works well on an MKIV, but I still get surprised every once in a while. Some people are running 8.5" wide wheels with a looowwww ET and have no idea how they fit up front without massive poke.

    Right now my wheels are flush with an 8" wheel with a final offset of ET30 up front and ET23 out back.

    Basic rule of thumb:
    - Higher offset (ET50 for example), wheels sit closer to car, have chance of hitting brake and suspension components
    - Lower offset (ET10 for example), wheels sits further out from car, lots of room for components but may poke past fender or impact fender on dips and bumps

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    There's more fitment than just offset... If you're running(for example) a 6.5" wide rim with ET 40, it will not clear the same as a 8" wide rim with ET 40..

    ET is a hard measurement, not a %age.

    For example, how much wheel will overhang towards the body from the mating surface:

    6.5"/2 = 3.25" + 1.6"(roughly 40mm) = 4.85"

    8"/2 = 4" + 1.6" = 5.6"

    and for the section of wheel outwards of the mating surface:

    6.5"/2 = 3.25" - 1.6" = 1.65"

    8"/2 = 4" - 1.6" = 2.4"

    In both cases you have an ET 40 wheel, but the 8" rim will be MUCH closer to the suspension components and body, and it will also poke out more. Just because the offset is the same, doesn't guarantee anything when going wider.
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    Senior Member thekatt has much to be proud of thekatt has much to be proud of thekatt has much to be proud of thekatt has much to be proud of thekatt has much to be proud of thekatt has much to be proud of thekatt has much to be proud of thekatt has much to be proud of thekatt has much to be proud of thekatt's Avatar
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    So how do spacers and adapters work? Do they add or subtract from the offset.

    Example:
    Say I have a wheel 5x120, 18x8, et35

    In order to fit that on a mk4, I would need a 5x120 to 5x100 adapter, which is 20mm thick. Would that make my offset 15, or 55?

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    Moderator EMSbyDay has a reputation beyond repute EMSbyDay has a reputation beyond repute EMSbyDay has a reputation beyond repute EMSbyDay has a reputation beyond repute EMSbyDay has a reputation beyond repute EMSbyDay has a reputation beyond repute EMSbyDay has a reputation beyond repute EMSbyDay has a reputation beyond repute EMSbyDay has a reputation beyond repute EMSbyDay has a reputation beyond repute EMSbyDay has a reputation beyond repute EMSbyDay's Avatar
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    depends on if its a + or - 35 offset. I dont know the wheel you are refering to but am almost sure it would be a +35 offset making the hub 35mm from the center of the wheel towards the front face of the wheel. By adding a 20mm adapter you are bringing the mounting surface back closer to the center of the wheel making it +15.

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    Veteran Member Neb has a reputation beyond repute Neb has a reputation beyond repute Neb has a reputation beyond repute Neb has a reputation beyond repute Neb has a reputation beyond repute Neb has a reputation beyond repute Neb has a reputation beyond repute Neb has a reputation beyond repute Neb has a reputation beyond repute Neb has a reputation beyond repute Neb has a reputation beyond repute Neb's Avatar
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    You can always assume when someone says et35 it's positive. The only time it's negative is if someone actually writes that. And that's rare to find in the VW/Audi world. VIP car with 10-13" wide wheels, yes they run the negatives..

    So et35 + 20mm adapter + et 15 which should fit on your car I might go with a 15mm adapter though instead of the 20 if you want a better fitment.

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    Senior Member thekatt has much to be proud of thekatt has much to be proud of thekatt has much to be proud of thekatt has much to be proud of thekatt has much to be proud of thekatt has much to be proud of thekatt has much to be proud of thekatt has much to be proud of thekatt has much to be proud of thekatt's Avatar
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    I was looking at these: BBS Diamond Black

    At what point (et) will I poke? I would prefer not to poke.

  9. #9
    Veteran Member Kooz has a reputation beyond repute Kooz has a reputation beyond repute Kooz has a reputation beyond repute Kooz has a reputation beyond repute Kooz has a reputation beyond repute Kooz has a reputation beyond repute Kooz has a reputation beyond repute Kooz has a reputation beyond repute Kooz has a reputation beyond repute Kooz has a reputation beyond repute Kooz has a reputation beyond repute Kooz's Avatar
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    Here is a great tool to help you compare wheel/tire combos.

    http://www.rimsntires.com/rt_specs.jsp


    Note: It doesn't allow you to enter wheel/tire combos that result in poke/stretch. That is fine by me because poke/stretch is lame IMO.
    Last edited by Kooz; 06-25-2010 at 06:24 AM. Reason: Added note/witty remark
    12V

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    Veteran Member doob is just really nice doob is just really nice doob is just really nice doob is just really nice doob is just really nice
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    Quote Originally Posted by Kooz View Post
    That is fine by me because poke/stretch is lame IMO.

    That's just because with ur wee one, nobody has ever been able to accuse you of poking or stretching anything!
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  11. #11
    Veteran Member Kooz has a reputation beyond repute Kooz has a reputation beyond repute Kooz has a reputation beyond repute Kooz has a reputation beyond repute Kooz has a reputation beyond repute Kooz has a reputation beyond repute Kooz has a reputation beyond repute Kooz has a reputation beyond repute Kooz has a reputation beyond repute Kooz has a reputation beyond repute Kooz has a reputation beyond repute Kooz's Avatar
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    Quote Originally Posted by doob View Post
    That's just because with ur wee one, nobody has ever been able to accuse you of poking or stretching anything!
    Yeah because it is more like RIPPING and TEARING.


    LOL!
    12V

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