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What is the wheel offset on 88.5 328s?

Discussion in 'Technical Q&A' started by Auraraptor, Dec 29, 2003.

  1. Auraraptor

    Auraraptor F1 World Champ
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    My car has the ABS wheels, but is pre ABS. what is the offset of the rims on the car? Is it the same as the +11 as the pre ABS 308/328s?
     
  2. Auraraptor

    Auraraptor F1 World Champ
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  3. Steve Magnusson

    Steve Magnusson F1 World Champ
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  4. Auraraptor

    Auraraptor F1 World Champ
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    I keep forgeting the old site and the new site archieves are not linked. Thanks!
     
  5. 348paul

    348paul Formula 3

    Dec 27, 2002
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    I have just had a set of 328 ABS wheels taken off a car to check the offsets.

    Front +38mm

    Rear +63.5mm


    This seems to contradict the previous 55mm dimension?



    Paul
     
  6. Auraraptor

    Auraraptor F1 World Champ
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    Interesting. My real question is, would I still be able to use the 360 rims (as you said, +32mm Front & +42mm Rear) on my car?
     
  7. davem

    davem F1 Veteran
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    Does anyone know if the ABS wheels on a 328 are the same as the ones on the Mondial?
     
  8. 348paul

    348paul Formula 3

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    Omar,

    Looks very possible - You would still have the interference problem of the rear shocks though.

    Best thing to do is take off your wheels and have a look on the inside of one of the spokes – it should have something like “C = 63.5” on the rears and “C = 38” on the fronts.

    Is your chassis number is after 76626

    Can someone confirm if the 328 did go through the stage of changing the wheels to the convex type but without the ABS system fitted?


    Paul
     
  9. Auraraptor

    Auraraptor F1 World Champ
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    When I was looking at buying a F512M (oh I was so close to a perfect example of my favorite car....:() I mentioned that I have a 88.5 328GTS, to which he said, on you mean a ABS prep-ed but non ABS car. I said exactly! And he told me of how many people think that 88.5 cars are ABS, but in fact no US 88.5 328 is ABS, but all the 88.5s are preped for ABS instead.

    Anyways, are you sure that the rears with a (reletively) narrow 255 tire will not work? 255s work on the 16s with no issue, so I am gussing that on 18s they should as well. That said, if there is no way around it without modding the suspension, I will keep looking for 2 spare fronts off of a 360 and just mount staggard tires.

    Will 360 fronts will work all the way around with no issue?
     
  10. Mule

    Mule F1 Rookie
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    Yes, the convex wheels don't really mean ABS. I have seen convex non-ABS cars and concave ABS cars (both 1988 cars). More to do with suspension and changing the hub.

    I have read here that the Mondial wheels are different, though I don't know how.

    I am getting ready to put these on my 1989 GTS. 17x8 and 225/45R17 front, 17x9 and 255/45R17 rear.
     
  11. Auraraptor

    Auraraptor F1 World Champ
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    Paul, so what offsets would I use then to adapt the 360 wheels (assuming the rears would work)?

    Isnt the natural offset of the wheels to high? I mean with 308 wheels you could add to the hub with spacers to make the offset about the same as stock 360. But now the hub's offset is going to be to much for the 360's rims and you can not "lower the offset" of a hub by adding spacers no?
     
  12. Auraraptor

    Auraraptor F1 World Champ
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  13. 348paul

    348paul Formula 3

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    Omar,

    Sorry - the thread got lost down the page!!

    Brain not in gear - The 360 wheels have quite a small offset compared to the likes of the 348/355 and you are quite right - if the offset on your 328 rears are 63.5mm the 360 wheels will be pushed out by 24.5mm and with an extra inch either side due to the larger rim you would be 2 inches outward from where your 328 rims are now !!

    Without opening up a large can of worms :) -The 355 has a 78mm offset on the rear!

    After writing the above it has caused me to open up a can of worms regarding the 348 with 360 rims which we know works without spacers etc.

    Can someone confirm my calculations or is it time for me to call it a day!

    The 360’s have a rear rim size of 10" & offset of +39mm. The 348’s have a rear rim size of 9" and an offset of +68mm. The difference in offset is -29mm . This will push the wheel outboard this amount plus 12.7mm - half of the increase in rim width?

    This is a total of 41.7 mm that the front of the rim would have moved outward, which I know, is way to much - (30mm spacers on standard 348 rims are a maximum)

    Something’s not quite right! – Help! :)



    Paul
     
  14. Auraraptor

    Auraraptor F1 World Champ
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    God this is so confusing. :p
     
  15. Auraraptor

    Auraraptor F1 World Champ
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    ok I got the pencil, paper, and calculator, I'll tell you what I come up with.
     
  16. 348paul

    348paul Formula 3

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    Omar

    I know what you mean!

    I am starting to doubt the 360 offsets that I have been given.

    Out of all the offset I have the 360 is the only one that I have personally not measured. The original figure I had on the rears were taken from actual dimensions measured. The 39mm figure is apparently what is cast onto the wheel.

    The 360 offset that I have seems too small - The 348 has +68mm the 355 has +78mm.

    360 wheels on a 355 - With that huge difference they would never go on!

    Looks like I am going to have to "personally" measure up a set!


    Ho hum!!

    Paul
     
  17. Auraraptor

    Auraraptor F1 World Champ
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    Hey Paul, just wondering, any developments?
     
  18. Auraraptor

    Auraraptor F1 World Champ
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    I posted the question on an other forum and here was the answer:
     
  19. Auraraptor

    Auraraptor F1 World Champ
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    http://www.usacomp.com/terms.htm

    Note how it calculates offset. The important fact is that it IS rim width dependant.

    Our buddy Mule gave me this site, I am going to use it and see what I come up with and post the results. This started as a novelty, but now I am determined to get results. :)

    I will post them.
     
  20. ChrisfromRI

    ChrisfromRI Karting

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    Nice looking wheels Mule!

    You may want to stiffen your front anti-sway bar and/or soften your rear antisway bar if you find the oversteer is excessive.

    Kind Regards, Chris
     
  21. Auraraptor

    Auraraptor F1 World Champ
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    #21 Auraraptor, Jan 29, 2004
    Last edited by a moderator: Sep 7, 2017
  22. Auraraptor

    Auraraptor F1 World Champ
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    #22 Auraraptor, Jan 29, 2004
    Last edited by a moderator: Sep 7, 2017
    RESULT: FRONT OFFSET WILL BE +18.7mm or about 3/4 of an inch (.736220in). AkA like if I had the stock rims on a 18.7mm spacer, or that if I switched to the 360, they would stick out due too offset by 18.7.
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  23. Auraraptor

    Auraraptor F1 World Champ
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    For the rears, I use a similar method.

    The 328 rear wheels are 203.2mm wide (8in*25.4mm/in). This means the centerline is 101.6mm. Now I subtract the offset, 63.5mm, to get 38.1mm, or what the distance from the front.

    The 360 rears are 254mm (10in*25.4mm/in). This means the centerline is 127mm. Now subtract the offset, 42mm, and get the distance from the front, or 85mm.

    Wow those are is pretty crazy numbers with a difference of 46.9mm!! (1.84645 inches!)

    The 360 fronts again are 203.2mm wide (8in*25.4mm/in). This means the centerline is 101.6mm. Now I subtract the offset, 32mm, and you get 69.6.

    The difference is a slightly more normal 31.5. (1.24015 inches)

    I think I am doing this right.
     
  24. Auraraptor

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    #24 Auraraptor, Jan 29, 2004
    Last edited by a moderator: Sep 7, 2017
  25. Auraraptor

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    #25 Auraraptor, Jan 29, 2004
    Last edited by a moderator: Sep 7, 2017
    Diagram 2. Note the Net is in black, and the respective sub-figures are in red and blue. The other thing to note is that in terms of width, both wheels cover the same region under the car. (while the 360 will stick out much more)
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