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Compomotive TS Offsets

Discussion in '308/328' started by Tifoso, Jan 14, 2021.

  1. Tifoso

    Tifoso Karting
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    Mar 8, 2005
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    Hi all,

    I have a set of the NLA 17" Compomotive TS wheels (8" front, 9" rear) on my '87 328 GTB. Because I am nuts, I am toying with the idea of an alternative set of wheels, and really like how the Comps sit on the car so I would like to match the Comp specs.

    I can't seem to get any information on the offsets of these wheels. I have tried the former vendor and Compomotive itself with no luck. I don't seem to have the paperwork. And a search on here revealed estimated offsets for the later (post-ABS) 328s, but not the 308/early 328 fitment. I could remove the wheels to see if the offsets are stamped somewhere, but haven't done that yet.

    Does anyone know the offset specs for this application?

    I've attached a few photos because....why not? :)

    Thanks!

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  3. derekw

    derekw Formula 3

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    I like the way they sit too. If you measure the offsets, please share. What tyres? Any mods to clear suspension? thanks
     
  4. GordonC

    GordonC F1 Rookie
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    Those wheels look gorgeous! If you decide to get rid of them, just PM me, don't worry about the rest of these guys. ;)

    The Ferrari 308 QV 16" wheel offsets are:
    16x7 front = 11.15mm
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    16x8 rear = 11.45mm
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  5. miketuason

    miketuason F1 World Champ
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  6. miketuason

    miketuason F1 World Champ
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  8. Tifoso

    Tifoso Karting
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    Thanks, I will definitely share the offsets if I'm able to obtain them.

    No modifications needed, and I'm lowered on coil overs.

    Ha! Thanks, yes, there have already been a few people reaching out.

    Just to be clear, I'm looking for the Compomotive offsets, not those of the stock wheels. Thanks again!
     
  9. miketuason

    miketuason F1 World Champ
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    Ok when get a chance I will measure the offset off my TS-17 as I have two brand new extra TS -17 in the box
     
  10. Mule

    Mule F1 Rookie
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    Some TS-17s were custom made like mine for my 1989 328. Remember, mine is a 1989, so it had convex wheels originally, and the Compomotives had to fit. The 308s and early 328s are different from the late 328s. They all weren't right off the shelf.

    For the later 328s that had convex wheels, these are the Compomotive measurements. Not the same for your 1987, but just FYI:

    Front: 8x17 at bead, actual overall 9x18.25, backspacing 6”, 1.5” positive offset, tires 225/45R17
    Rear: 9x17 at bead, actual overall 10x18.50, backspacing 7”, 2” positive offset, tires 255/45R17
     
  11. Meister

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    Yes Compomotives could come custom offsets.

    Take a half an hour and take two of them off and see. If they are not stamped on the inside of the wheel spokes, find the center of the rim then measure the distance from that center to the face of the mounting flange and that is your offset.
     
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  13. miketuason

    miketuason F1 World Champ
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  14. Tifoso

    Tifoso Karting
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    Thanks all.

    There are no offsets stamped inside the wheels.

    In terms of measuring offsets, I won't be able to get an accurate measurement unless I remove the tires, which I'd rather avoid....
     
  15. Meister

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    #12 Meister, Jan 16, 2021
    Last edited: Jan 16, 2021
    you'll get it accurate enough with the tires on, just estimate the thickness of the outer lips.

    for instance the fronts are 8" wide. Take your tape or something that is 8" wide, space it equally between the front and back lips (on the inside of the rim) and there is your center. Do that on an opposite spot on the rim, find another piece of wood, straight edge. hold the straight edge on the two spots and measure to the mounting flange.
     
  16. Meister

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    general idea, plenty accurate as every front and rear lip I've seen on wheels are equal thickness so simply find the center on the inside of the rim
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  17. HotShoe

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    Compomotives are three piece wheels so it’s simply a matter of getting the correct inner/outer barrel combination.

    I think I have an email from the company stating the original spec. I’ll try to find it.
     
  18. Tifoso

    Tifoso Karting
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    That would be fantastic, Hot Shoe -- thanks!

    I contacted Compomotive itself, but they told me they stopped making the TS 10 years ago and no longer have the information. The company that originally sold me the wheels (US Compomotive distributor, Motorsports Specialties) no longer exists.
     
  19. Tifoso

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    I was not able to get any hard offset data, so I removed my front wheel and tried to measure everything as accurately as I possibly could. I did not measure the back wheel, as I assume the offsets are identical. Here's what I got for my front 17x8 wheel:

    Total wheel width (edge to edge): 235mm (9.25")
    Backspace: 130mm
    Frontspace: 105mm
    Offset: 12.5mm

    Here's a crude drawing I did of the measurements:

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