Page 1 of 2 12 LastLast
Results 1 to 25 of 34

Thread: How to Calculate Offset after Lip and/or Barrel Change

  1. #1
    Join Date
    Oct 2009
    Location
    Dallas, TX
    Posts
    4,294,967,248

    Default How to Calculate Offset after Lip and/or Barrel Change

    Made this a while back...


    Before we start, please use Roan's (zeroluxxx) DIY Guide on measuring wheel parts so you get the correct calculation to start out with: [ http://forums.vwvortex.com/zerothread?id=3773369 ]


    Maybe this could help some people as I know it can get confusing. Let's start with my wheels as an example:

    Fronts:
    BBS RS320
    17x8 ET43 (7" barrel + .5" center + .5" lip)

    Rears:
    BBS RS300
    17x9 ET53 (7.5" barrel + .5" center + 1" lip)

    Adding the center's thickness into the equation only works if your wheels are sandwich mount (lip, face, barrel).

    I moved the 1" drop lips from the rear to the front, resulting in:
    17x8.5 ET37 (7" barrel + .5" center + 1" lip)

    Now how did I get the final offset? Using [ http://www.1010tires.com/WheelOffsetCalculator.asp ]. I input the stock set up (8 ET43) and input the new width (8.5) and got to ET37 to maintain the same inner position because you aren't changing anything except the outer position.

    I have noticed for every .5" you go out (pattern), while maintaining the same inner position/clearance, you will lower your offset by ~6mm (6.35mm to be exact (25.4 / 4 = 6.35). I have also noticed the outer position will go out 12mm (using the calculator, it gives you 12mm) (12.7 to be exact; 25.4 / 2 = 12.7)).

    Then I got 1.5" lips to replace on the rears resulting in:
    17x9.5 ET47 (7.5" barrel + .5" center + 1.5" lip)

    Now what about if I changed the barrels up? You'd see the same pattern, but the outer position stays the same, whilst the inner position goes in or out (depending if you get smaller or larger barrels, of course).

    Let's use my stock fronts for example (17x8 ET43 with a 7" barrel):

    I'll put a 6.5" barrel on it, resulting in: 17x7.5 ET37 (6.5" barrel + .5" center + .5" lip). Notice the pattern again; .5" on that inner position results in 6mm lower offset (again, technically 6.35mm, easier to round down). Same thing with the inner position, it would gain 12mm (12.7 to be exact).

    Well, what if I do both [smaller barrels and bigger lips]? You basically use the same formula/input the same things, but one at a time.

    For example, lets use the stock fronts again but put .5" smaller barrels and a 1.5" lip on it.

    Stock we know is 17x8 ET43 (7" barrel, .5" center + .5" = 8")
    .5" smaller barrels we know results in 17x7.5 ET37 (6.5" + .5" + .5" = 7.5)
    Now lets add that 1.5" lip to the equation: 6.5 + .5 + 1.5 = 8.5"
    Final specs would be: 17x8.5 ET24 (which would gain 12mm inner clearance and outer position would "poke" 26mm more than stock lips).

    Hope this helps
    Quote Originally Posted by Jesus Christ View Post
    if "life, liberty and the pursuit of happiness" doesnt include being able to buy a huge veiny motherfucker then the declaration of independence isnt worth the hemp it was written on.
    Quote Originally Posted by Jedidiah View Post
    he speaks the truth.. he doesn't even have the -- -- eyes.

  2. #2
    firelizard Guest

    Default

    That's a lot of text to essentially say:

    Lip increase, converted to MM = net reduction in offset
    Barrel increase, converted to MM = net increase in offset

    Lip and Barrel changes: net reduction by lip + net increase by barrel = net change in offset (could be negative or positive)

  3. #3
    Join Date
    Jul 2010
    Posts
    14

    Default

    ^^^^^i was thinking the same

  4. #4
    Join Date
    Jul 2010
    Location
    Hungary
    Posts
    7

    Default

    Hi! I want to by an e46 m3 rim for my e36 320i. I dont know if the rim will work perfekt without the modification on the fender etc..., on the car. There isnt any e46 m3 rims near here, so i cant try it on. The rims are 8JX18 ET/IS:47 9JX18 ET/IS:26 .

  5. #5
    Join Date
    Oct 2009
    Location
    Houston
    Posts
    305

    Default

    Quote Originally Posted by firelizard View Post
    That's a lot of text to essentially say:

    Lip increase, converted to MM = net reduction in offset
    Barrel increase, converted to MM = net increase in offset

    Lip and Barrel changes: net reduction by lip + net increase by barrel = net change in offset (could be negative or positive)
    changing the width x amount only changes the centerline x/2 which is where offset is measured from. all you ever need to know:

    +1" lip = -12.7mm offset
    +.5" lip = -6.35mm offset
    -.5" lip = +6.35mm offset
    -1" lip = +12.7mm offset

    +1" barrel = +12.7mm offset
    +.5" barrel = +6.35mm offset
    -.5" barrel = -6.35mm offset
    -1" barrel = -12.7mm offset

  6. #6
    Join Date
    Jan 2010
    Posts
    44

    Default

    The easiest way to do this is look at a Backspace to offset chart and calculate...

    Find your current width and offset then trace directly down to desired width it gives you roughly your new offset (add or subtract accordingly)

  7. #7
    Join Date
    Aug 2009
    Location
    So Cal___Wii Wii Land
    Posts
    297

    Default

    saved.
    2006 M3 Cabrio
    2004 ZHP Cabrio

    /stanceworks\

  8. #8
    Join Date
    Sep 2010
    Location
    CA
    Posts
    341

    Default

    Quote Originally Posted by firelizard View Post
    That's a lot of text to essentially say:

    Lip increase, converted to MM = net reduction in offset
    Barrel increase, converted to MM = net increase in offset

    Lip and Barrel changes: net reduction by lip + net increase by barrel = net change in offset (could be negative or positive)
    I was thinking the same

  9. #9
    Join Date
    Nov 2010
    Location
    Califlorina
    Posts
    937

    Default

    .
    That chart is really helpfull ....... . I am trying to figure out if I can fit a 16x8.5 -6mm wheel

    I have 16x8 +12 .. . so according to that chart, if my math is right... I think I need 24mm of spacers to replicate a 16x8.5 -6mm???

    .... assuming I will use the same tires is my math correct???,,,,, it's gonna be a really tight fit,, every mm counts

  10. #10
    Join Date
    Jun 2010
    Location
    California
    Posts
    5,489

    Default

    That chart is awesome. Anything saving me from doing math gets a thumbs up in my book.

  11. #11
    Join Date
    May 2009
    Location
    NYC
    Posts
    4,934

    Default

    Quote Originally Posted by firelizard View Post
    That's a lot of text to essentially say:

    Lip increase, converted to MM = net reduction in offset
    Barrel increase, converted to MM = net increase in offset

    Lip and Barrel changes: net reduction by lip + net increase by barrel = net change in offset (could be negative or positive)
    lol ok but you're wrong. thanks anyway

    IG: @_olliee

  12. #12
    Join Date
    Jul 2010
    Posts
    31

    Default

    i was going to say easiest way is just know the backspacing . If you have a 4" backspace on a 9" wheel and you add a 1/2" wider lip then just figure the offset on a x9.5 with a 4" backspace.

  13. #13
    jamesklass Guest

    Default

    I know it can get confusing. Let's start with my wheels as an example



  14. #14
    Join Date
    Nov 2009
    Location
    Renton, WA
    Posts
    561

  15. #15
    Join Date
    Feb 2010
    Location
    Central NC
    Posts
    517

    Default

    nice thread. i suck at math. this will help. lol
    i know its old, whatever.
    I haz 4 wimz. need 4 more.

  16. #16
    Join Date
    Jun 2011
    Location
    McLean, VA
    Posts
    111

    Default

    I have work vs-xx's that are 18x8 et34 with 1.5" lips and im putting on 2.5" lips. So will they be 18x9 et9 or et21? i keep being told different from multiple people.
    Thanks

  17. #17
    Join Date
    May 2010
    Location
    Bulgaria / EU
    Posts
    2,542

    Default

    there are wheels that the face can be reverse or sandwich mounted, then we can have two wheels with same lip and barrel sizes but different offset...

    i think Capt. Obvious's way of measuring is the best in this case...

  18. #18
    Join Date
    Mar 2013
    Location
    Miami FL
    Posts
    108

    Default

    I think the problem with his method is he is measuring the outer width of the barrel not bead to bead. wheels to my understanding are measured bead to bead and the offset is determined by that so If you measure from the outer rim as he has shown your adding another inch in most cases to actuall measure size of the wheel... great thread.....
    " You made your choice, I made my choice, at the end of the day if you don't like my choice it's your problem not mine"

    New Z build
    http://www.stanceworks.com/forums/sh...99#post1498599

    New M3 DD build
    http://www.stanceworks.com/forums/sh...65#post1498765


  19. #19
    Join Date
    Feb 2010
    Location
    Central NC
    Posts
    517

    Default

    I thought wheel width was bead to bead and offset was outer to outer?
    I haz 4 wimz. need 4 more.

  20. #20
    Join Date
    Jun 2013
    Location
    Box 337, Brockport, New York 14420, USA.
    Posts
    10

    Default

    Great info! I wonder if this is the same for all wheels, or just BBS? It would make sense to have an understood way of measuring, but you never know.

  21. #21
    Join Date
    Jan 2011
    Location
    Lipik, Croatia
    Posts
    318

  22. #22
    Join Date
    Sep 2013
    Posts
    2

    Default

    wow... this is good thread. just anyone know about Honda CB4 spect1 model. i just want to know what it's having common errors.

  23. #23
    Join Date
    Nov 2010
    Location
    Bucharest, Romania
    Posts
    844

    Default

    Hi guys,

    I have a little dilemma and I hope some of you ran into this so you can give me some piece of advice. I read the whole thread but I'm still confused.

    I have a set of OZ Futura 18x8J, ET 35, 1.5'' lip that I run with 24mm adapters and 205/40/18 tires.



    I now want to change the lips with new ones measuring 2.75'' to make the wheels 9.25'' wide and put 215/40/18 tires on them. Will that change the offset of the rim? Since the width of the rim will increase, I plan to mill down the adapters a few mm to a smaller size until it gets to the fitment I want (probably similar to above). Do you guys think it will work?

    P.S: I would prefer not to do any fender work. I like them the way they are
    Last edited by daniel_lucian; 01-23-2014 at 05:49 AM.

  24. #24
    Join Date
    Jan 2014
    Posts
    4

    Default

    Quote Originally Posted by daniel_lucian View Post
    Hi guys,

    I have a little dilemma and I hope some of you ran into this so you can give me some piece of advice. I read the whole thread but I'm still confused.

    I have a set of OZ Futura 18x8J, ET 35, 1.5'' lip that I run with 24mm adapters and 205/40/18 tires.



    I now want to change the lips with new ones measuring 2.75'' to make the wheels 9.25'' wide and put 215/40/18 tires on them. Will that change the offset of the rim? Since the width of the rim will increase, I plan to mill down the adapters a few mm to a smaller size until it gets to the fitment I want (probably similar to above). Do you guys think it will work?

    P.S: I would prefer not to do any fender work. I like them the way they are
    Based to what I understand, your offset will be lower (something around et8 ) therefore you will be poking. The only way you can get it done and be able to run it in your car is redrilling your wheels and ditch the adapters. (someone correct me if im wrong).

  25. #25
    Join Date
    Apr 2014
    Posts
    1

    Default help

    Reading this made me more confused. I have a set of BBS RS. 17x8 +19 and 17x9 +0. What size lips would I need to make it 17x9.5 all around?

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •