15" wheels & 2" drop

Discussion in '1974 - 1978 Mustang II Talk & Tech' started by kcobra302, Mar 18, 2009.


  1. kcobra302

    kcobra302 Founding Member

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    recommendations please

    i dropped my king 2" inches in the front and 1" in the rear. i am having a tough time getting a 15" wheel with a decent size tire to work in the front. i am currently running a 15x4 and would like to change it out to put a little more rubber on the ground.

    i tried a 15x7 @ 3"3/8 backspacing and a 225-50-15. will not clear. tried a few others but i just can't get it to work. hits inside the wheel and the wrap for the chin spoiler.

    anybody have king with a dropped front end?

    checked out the tire/wheel thread but it appears everybody is running stock height.

    thanks,
    kcobra302
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  2. Dano78

    Dano78 Founding Member

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    My Car isn't a King but I did have the Cobra air dam on my car earlier on. The rear is dropped 1" and the front 2-3" (can't remember for sure) The wheels I have are 14x7s but I can't remember the backspace on them.

    My front tires are P195/60-14s
    Overall dia - 23.2 inches
    Section width - 7.68 inches
    Sidewall Height - 4.61

    Comprarable 15" tire sizes would be:
    P195/55-15
    Overall Dia - 23.44
    Section Width - 7.68
    Sidewall Height - 4.22

    P205/50-15
    Overall Dia - 23.07
    Section Width - 8.07
    Sidewall Height - 4.04

    P205/55-15
    Overall Dia - 23.88
    Section Width - 8.07
    Sidewall Height - 4.44

    P215/50-15
    Overall Dia - 23.46
    Section Width - 8.46
    Sidewall Height - 4.23

    P225/45-15
    Overall Dia - 22.97
    Section Width - 8.86
    Sidewall Height - 3.99

    Some of these tire sizes may not even be available. I just pulled them up using a tire size calculator. But you may never know, depending on each tire manufacturer.

    Backspace on the wheel is a big player on where the wheel is located as you turn it (the steering wheel). More backspace will probably help with preventing the wheel/tire combo hitting the front air dam, but on II's will cause rubbing problems with the inner frame and the wheel itself may rub the control arm from the excessive backspace. This is why wheel spacers were used on alot of the later model mustang wheels when used on IIs. (IIRC they are 4.25" on the backspace) Typical 7" wide wheels are usually 3.5 to 4" on the backspace depending on manufacturer and style of wheel.
    If you're ok with the 'rubber band wraped around the rim' look then going to a lower profile say like a 45 or 50 series (depending the the width of the tire --see below-- ) you might be able to get it to clear. I can't stand that look and to be honest i don't care for how short my tire sidewall is on my front wheels. It's borderline acceptable for me though. You also what to make sure that the tire's Section Width is enough to cover the width of the rim. For a 7" rim, 195 is cuttin it awful thin. Otherwise you'd get that look as if the tire was stretched wider to fit the rim and providing none or negitive sidewall bulge. (where the rim would stick out farther than the rubber of the tire. - typical with lowriders)



    A little info on how to understand and figure out tire sizing:

    Section Width
    Following the letter(s) that identify the type of vehicle and/or type of service for which the tire was designed, the three-digit numeric portion identifies the tire's "Section Width" (cross section) in millimeters.

    P225/50R16 91S

    The 225 indicates this tire is 225 millimeters across from the widest point of its outer sidewall to the widest point of its inner sidewall when mounted and measured on a specified width wheel. This measurement is also referred to as the tire's section width. Because many people think of measurements in inches, the 225mm can be converted to inches by dividing the section width in millimeters by 25.4 (the number of millimeters per inch).

    225mm / 25.4 = 8.86"

    Sidewall Aspect Ratio
    Typically following the three digits identifying the tire's Section Width in millimeters is a two-digit number that identifies the tire's profile or aspect ratio.

    P225/50R16 91S

    The 50 indicates that this tire size's sidewall height (from rim to tread) is 50% of its section width. The measurement is the tire's section height, and also referred to as the tire's series, profile or aspect ratio. The higher the number, the taller the sidewall; the lower the number, the lower the sidewall. We know that this tire size's section width is 225mm and that its section height is 50% of 225mm. By converting the 225mm to inches (225 / 25.4 = 8.86") and multiplying it by 50% (.50) we confirm that this tire size results in a tire section height of 4.43". If this tire were a P225/70R16 size, our calculation would confirm that the size would result in a section height of 6.20", approximately a 1.8-inch taller sidewall.


    Here are a couple of useful tire calculators that I use from time to time:

    Tire Dimensions Made Simple - Discount Tire

    Tire size calculator
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  3. Dano78

    Dano78 Founding Member

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    A couple of pics to show you my IIs stance... It's pretty low in the front. The saddle height on my floor jack, when all the way down, is 3.75 inches and I usually have to lift by the bumper with my shoulder a bit to get the jack under the main crossmember. So yeah... It's low.... probably a little too low. :rolleyes:

    [​IMG]

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    [​IMG]
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  4. kcobra302

    kcobra302 Founding Member

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    thanks for the info dano.

    i have been looking at tire sizes for a long time. i really wanted to go with a 25" tall tire but i just can't get it to work.

    i just hate to go out and buy a size, then have it not fit.

    i am thinking a 15 x 6 wheel with a 205 or 215. there are several companies making the 50, 55 & 60 series in those widths. as you said its just working with the overall height of the tire.

    i still have the original lacy spokes mounted up, so i am going to pull them down to see what was mounted on them and compare them to what i have to see if i can come up with something in the middle.
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  5. Dano78

    Dano78 Founding Member

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    The key is you just gotta have an 'in' with a smaller tire shop or some larger chain stores that is willing to mount the tire and try it on the car. There is a couple smaller tire shops here in town that do this for me. To them, it couls be another sale to they realy on really good customer service, which may mean trying on a few different tire sizes.

    Unless you're stuck with a certain set of wheels, shop around and see what kind of backspacing you end up with on different wheels and their widths. Adjusting the backspace might do your clearance some good.

    On my old '78 Cobra II I had 14x6s on the front of it with the same P195/60-14s that are on the one in the pics above and the sidewall looked a whole lot better. The 195's are just too narrow for a 7" rim, even if you go as tall as 70 series, just dont' look right.

    Here's some pics of my '78 Cobra II I had years ago in New Mexico. It's got 14x6 Roadrunners all around with P195/6014s on the front and P235/6014s on the rear.
    [​IMG]
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  6. Dano78

    Dano78 Founding Member

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    Oh and if anybody asks, Yes both those exhaust pipes are functional and no I didn't remove or modify the fuel tank or anything else of the car to get 'em there. :) Just had a REALLY good exhaust guy.... (1 7/8 pipes ... V6 car)
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