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Need help on proper offsets on 18x9.5 and 18x10.5 wheels

Discussion in 'Suspension Modifications' started by tegan, Nov 12, 2012.

  1. tegan

    tegan New Member Established Member

    Sep 11, 2012
    Greensboro NC
    Hi Guys,

    I know this topic has been talked about to death so I apologize for bringing it up again but I can't find the info that I need. I recent bought an 03 cobra vert in stock form and starting to convert it into my vsion. I have H&R race springs coming with all the supporting gear. I am also looking for wheels. I found a wheel that I like that is a BBS knockoff. The company that makes it is Varrstoen. It looks like their bigger in the rice market. They suggest the 18x10 for the back with a 15mm offset and a 18x9.5 in the front with a 12MM offset. I have done my research and understand what the numbers mean but that offset seems really low to me. All the mustang specific wheels have offsets on the 20's. They also offer a 18x9.5 in 22 offset and the 18x10.5 in 25MM offset. What do you think? What offset should I get. I cannot find pics of it on a cobra. I do not want the wheels to stick outside the fenders like some of the imports. Am I missing something? I do not want any clearance issues and prefer not to roll fenders or add spacers.

    Thanks Guys.
  2. SpectorV

    SpectorV Active Member Established Member

    Mar 25, 2005
    Birmingham AL
    the lower the car is VS stock height the more tucked in the front wheel is due to how the front suspension compresses. My 18x9 TF wheels are 2.89 front spaced if I remember right (width - backspacing - frontspacing)

    So that value around 3 inches works good~

    for 9.5 wide that would be an offset of about 1.75 inches or 44.45mm, but that extra .5 inside might cause rubbing on the sway bar etc when at a full turn~

    for comparison the 17x9 cobras (oem 03 wheels) are 6.1 back spaced if i remember right (2.9 front spaced)~

    for the rear 3.75 inches is pushing it (with fender rolling needs). I think 3.75 looks best, but some do 4 ( a bit much with a tire that goes past the rim and will require rolling on a lowered car for sure)

    10.5 rim would mean an offset of 1.25mm or 31.75~ to be at 4 inches frontspaced, to be safe 3.75 or 3.5 could be used and that would put it at 38.1mm or so feel free to double check my math. As far as I know 3.5" frontspacing on rear with IRS will clear the fender lip with a normal size tire (should easily even with a little overlap). Mine are 3.75 and I rub a bit on one side :(

    This is on an IRS car of course.
    Last edited: Nov 12, 2012
  3. koffebean00

    koffebean00 New Member Established Member

    Oct 14, 2003
    Atlanta, Ga
    Order 18x9.5 +22 fronts and they'll fit fender flush. 10.5 +15 rears if you want fender flush no spacers or +25 if you want them to sit inside the fender. +15 will be an aggresive fitment and you'll probably need to roll the fenders with wide meats.
    Last edited: Dec 4, 2012

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