235/60/15 on front of duster?

Tires and Wheels (Mopar Hubcaps Too)

  1. thanson_mopar

    thanson_mopar Well-Known Member

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    So I am asking because when I do a search some people say no way and others say they work fine?! I am trying to run P235/60R15 Mickey Thompson S/T tires on all four corners on my 74 duster. 4 wheel disc brakes if that makes any difference. I am wondering if they are going to work on the front or not. I'm going to run 15x8 steel wheels with 4" of backspacing. Anyone specifically run these Mickey T tires? Thanks

    here are specs directly from MT if that helps
    Sportsman S/T™
     
    Last edited: Apr 7, 2021
  2. DionR

    DionR Well-Known Member

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    I tried some 235/60R15's on cop car wheels on the front of my Duster and it needed more backspacing/positive offset to work. I think those had 4.25" backspacing? I though it looked kind of funky.

    But I don't remember if I could have driven it like that, I only did it out of curiosity and swapped the 14" wheels back on.

    One issue is a 15" wheel has a limit to how much offset will work before it starts hitting the UCA, BJ and/or tie rod end. That's one advantage to a 17" or 18" wheel, you can push the tire further in because they clear the suspension better, but even a 17" has a limit.

    You can probably make it work by pushing your fenders around, but I would look at more back spacing after finding out what the limit is.
     
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    • 72bluNblu

      72bluNblu FABO Gold Member FABO Gold Member

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      BBP disk brakes? No way. Not on a 15x8” with 4” of backspace. Not unless you adjust the ride height up so it looks like a 4x4.

      SBP disks, maaaaaaybe. Still be super tight on the fender. Probably still have to move some stuff around to make that work.
       
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      • DionR

        DionR Well-Known Member

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        I missed that he was talking about an 8" wheel. Mine were on 7" wheels.

        After the multiple calculations to convert backspacing to offset (sorry, minor :poke: at someone who shall remain un-named), that tire is going to be at least 3/4" further out than mine were, and that is without including the extra width the 235 is going to have on an 8" rim compared to a 7" rim.

        I think Blu is right on the money. Assuming BBP (like mine), really doubt you will get those tires and rims to work on the front.
         
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        • thanson_mopar

          thanson_mopar Well-Known Member

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          Yep, BBP.....bummer. I really like the look of 15" wheels on these cars but might just have to get into a set of 17's.
           
        • thanson_mopar

          thanson_mopar Well-Known Member

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          hypothetically If I were to be looking at buying a set of these American racing wheels what do you think I could get away with on the front?

          Available as a 17x7 and 17x8 (4 inch backspacing and 4.5 inch backspacing respectively)
          Also max tire size?

          American Racing VN3097765: VN309 Series Torq-Thrust Original Wheel Size: 17" x 7" | JEGS

          American Racing VN3097865: VN309 Series Torq-Thrust Original Wheel Size: 17" x 8" | JEGS

          I'm not racing by any means....just a spirited driver for the corners!
           
        • DionR

          DionR Well-Known Member

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          Here is my '74 with BBP disks and a 15x7 cop car wheel with a 235/60R15:

          P7230011.JPG

          P7230013.JPG

          It looks better than I remember, but still sticks in my head that it was too close.

          Depending on what the max backspacing is that would fit for a 15" wheel, I would guess you could get it to fit, but I would run more offset than the cop car wheels.
           
        • DionR

          DionR Well-Known Member

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          Here's a post were @autoxcuda said max backspacing on a 15" rim is 4.5" with a stock UCA.

          73-76 A-Body Offset

          That would push the tire in another 1/4" from where mine ended up.

          So maybe a 15x7 with 4.5" BS would work?

          One thing you could try is one of those online calculators and plug in a know wheel and tire combo on your car and then the new sizes and see how it moves the tire around. Based on that you could get an idea of how well it might fit.
           
        • autoxcuda

          autoxcuda Well-Known Member

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          a 15x7 with 4.5 backspacing is most likely going to be a custom spec rim.

          I run 15x8 with 4.5 backspacing BUT with much smaller diameter 245/50/15 tire.

          with 235/60/15, 15x7, 4.5” backspace, and BBP disks is going to be real close. So close that alignment settings and component parts will create variation between to same model where one rub and one doesn’t.

          Probably need bottom fender support moved out. Might need fender lipping.

          just too close to call. You’re on your own to use methods to overcome what you end up with.
           
        • - Marvin -

          - Marvin - Well-Known Member

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          prospekte-056-jpg-jpg.jpg

          VREDESTEIN PROTRAC 235-60-15 all around on Rallye Wheels and front disc-brakes (stock).

          Works fine....
           
        • thanson_mopar

          thanson_mopar Well-Known Member

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          I assume small bolt pattern? Also whats the width and backspacing on the front wheels?
           
        • - Marvin -

          - Marvin - Well-Known Member

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          Right - small bolt pattern.

          Width of the Rallye Wheels should be 6 inch - as far as I remember

          I presume backspace should be the same as on regular 14' Rallye Wheels, but I have not measured it...
           
          Last edited: Apr 8, 2021
        • - Marvin -

          - Marvin - Well-Known Member

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        • 72bluNblu

          72bluNblu FABO Gold Member FABO Gold Member

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          It “works fine” because with the SBP your track width is like a 1/2” narrower.

          And, your 235’s shouldn’t me mounted on a 6” rim. They’re being squeezed down and will be narrower than the advertised spec, which is measured on a 7” wide rim.

          And, that’s a Demon. Dart fenders have a longer opening than Duster fenders. The clearance for the width is the same, but the height of the 235 may cause additional problems on a Duster because the rear corner of the fender opening will also be very tight, not just the front.

          Even with the SBP, if you mounted those tires on a 15x7” like they should be your clearance might become an issue.

          Like DionR I ran a set of 225/60/15’s on my Duster on a set of 15x7’s with a 4.25” backspace. 73+ BBP disks. They cleared, but barely. The clearance to the rear corner of the fender was actually the tightest spot on my car, although the clearance to the fender lip was really tight as well. No way 235’s would have worked. But that’s why it’s important to make all of the information available- BBP makes a difference. Backspace makes a difference. Body style makes a difference. And mounting the tires on a narrower rim than recommended makes a difference.
           
        • thanson_mopar

          thanson_mopar Well-Known Member

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          With these 15x8 rims with 4 inch of backspacing it looks like I might even have trouble fitting 225/60r15’s....If I cant even run those then I will sell these wheels and look at different options.
           
        • kesteb

          kesteb Well-Known Member

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          They will work, just needs a little work.

          Fenders: 68 Dart
          Suspension: Stock rebuilt '74 with boxed LCA and "340" TBars and +73 BBP disks
          Ride Height: 11" from level ground to the front K-member bolt.
          Rims: Crager 10 D Window, 15x7 - 4.25 back space
          Tires: Cooper Cobra GT - P235x60

          The 4.25 back spacing will but the rim about 1/4" from the zerk fitting on the upper ball joint. Now the work part, you need to do the following:

          Measure 1 3/8" forward from the current lower strut rod bolt hole. Make a mark and drill it out. Adjust the strut rod to the new position. This pushes out the lower front corner of the fender and depending on the car, it may be all that needs to be done.

          Next mesasure 1/2" towards the front from the lower front corner of the fender. Make a mark.

          Next measure from that same lower front corner, 1 1/2" upwards. Make a mark.

          Now take a cut off wheel and connect the marks. Your tires will now clear and nobody will notice.

          At this ride height you may need to take off the upper fender strut bar and gently bend the tab up or the tire will hit them.
           
        • 72bluNblu

          72bluNblu FABO Gold Member FABO Gold Member

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          A 15x8" with 4" of backspace and BBP disks is a terrible wheel spec. The outside lip of that rim is like 1" further out than the 18x9's I run. Even a 15x8 with a 0 offset is 4.5" of backspace, and that's still terrible. With a 15x8" and a 4" backspace you'll be hard pressed to get anything to clear, even stretching a narrow tire on there. A 225/60/15 is the narrowest tire that should be mounted on a 15x8". You need a different rim up front.

          A 15x7 with 4.25" of backspace is a stock spec BBP rim, so there shouldn't be any clearance issues.

          Could you include a picture of your height measurement? Which K member bolt are we talking about? The K-member to front radiator support brace bolt or the forward K-member to frame rail bolt?
           
        • kesteb

          kesteb Well-Known Member

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          There are 4 bolts that hold the k-member in place. I am referring to the front 2. And no, 4.25 is not the standard BBP backspace. OEM Chrysler wheels are always centered. A 15x7 rim would have 3.50" backspace. Add 3/16" for the lip. The original OEM Chyrsler Cordoba steel 15x7 rims that I have don't fit. The backspacing is wrong.
           
        • AJ/FormS

          AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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          I bought a pair of custom 15 x8 Rallys with a 4.5 bs to fit on my 68 Barracuda, with KH brakes. After spending hours and hours to make it work,according to the suspension, I sent the wheels to a local shop and had them move the Spider to where it needed to be.
          Then I installed a pair of sticky 245/50-15s and thought I was ready to go. As I was backing off the 4-post hoist and riding the brakes, I heard a noise and stopped. Come to find out the tire was rolling up the corner of the fender. So out came the tin-slips and solved that problem. Then, on the round the block run, I heard other noises so I fixed those with 1.03 T-bars. Then out on the hiway, those tires followed every wagon-rut in the road. I got some tools and on the hiway, played with the toe-in and got it as good as it could be.
          About a month or two later, those stickys were bald, right across the tread very nicely. I replaced them with 235/60-14s and all my problems were solved except
          I had to slow down in the turns a tad,lol.
          The 14s were a tad taller than the 15s, about 25.1, to 24.3(about the same as factory tires were). She's been wearing 235s ever since.
          The thing about 235s on the front and 295s with 10x2 drums on the back is, with no Proportioning, man does that beast scrub speed, when I throw out the anchor.
           
          Last edited: Apr 29, 2021
        • Slantsix64

          Slantsix64 Well-Known Member

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          on my brothers 68 barracuda with BBP front end we did 15x6 with 4.5 back space using a 225 60 15 tire came out nice, with the rear tire being 255 60 15
           
        • 72bluNblu

          72bluNblu FABO Gold Member FABO Gold Member

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          Ok, let's correct a whole bunch of stuff. A "centered" 15x7 would have 4" of backspace, not 3.5". A 15x7" rim is 8" wide outside lip to outside lip (7" is the width where the tire seats), and backspace is measured outside lip to wheel mounting surface. So a 0 offset 15x7 has a 4" backspace. You can check this on any wheel calculator.
          Screen Shot 2021-04-29 at 5.47.38 PM.png

          OE Chrysler wheels weren't "always" anything. OE SBP wheels were typically 0 offset. OE BBP wheels on the other hand were often +6 offset. Which makes a 15x7 a 4.25" backspace. You can see that with these very much OE police rims. You can see the 4.25" backspace measurement, as well as the original stamping including the part number, size and manufacturing date. These are from '84, but all of the steel police wheels were the same, 15x7, 4.25" backspace. There was the same design in a 15x8 but those were truck wheels and had a 4.5" backspace. I didn't say all BBP 15x7's had a 4.25" backspace, but it is a factory spec, as I said.
          IMG_0553.jpeg

          As for your height measurement, that's kinda what I thought. That measurement means your frame rails are sitting on your LCA bumpstops though. I don't drive the lowest car around, but it sits pretty low. On my car the measurement to the front K frame bolt is ~12". More importantly, my LCA to frame measurement is only about 1". Now, a bunch of stuff goes into that measurement, like tire height. Except your tires are 26" tall and mine are 25.7", so your tires are actually raising that number. I also have tubular LCA's, which increases my LCA to frame number and allows for more travel.

          So, bottom line is if you're not running 2" drop spindles to get 11" at the front K frame bolt you pretty much have to be completely bottomed out on your LCA's. Now I suppose it's possible you're running a TON of rake, which would effect the height at that K member bolt since its forward of the spindle. But with little .88" diameter torsion bars it doesn't really matter, you won't have enough suspension travel at that height to have functional suspension with those bars.

          Unless I'm somehow misunderstanding how you're taking that height measurement. Which is possible, which is why I asked for a picture. Same would go for your LCA's at this point.
           
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          • kesteb

            kesteb Well-Known Member

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            Update: The ride height is actually 14”, I forgot to factor in the body of the tape measure.
             
          • 72bluNblu

            72bluNblu FABO Gold Member FABO Gold Member

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            Well that makes a gigantic difference. That measurement would mean you're pretty close to the factory ride height, as my car is lowered about 2" from factory. Lots of people actually run a little lower than factory though, and even a little bit makes a big difference if you're trying to maximize tire size.
             
          • Topless69

            Topless69 Well-Known Member

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            Interesting 72bluNblu - I always thought 15x7 police rims were 4.625 backspace.
            Does all this mean a 15x7 4.0bs rim with 225/60 tires and aftermarket bbp disc setup won’t fit my ‘69 Barracuda with stock ride height?
             
            Last edited: May 12, 2021
          • 72bluNblu

            72bluNblu FABO Gold Member FABO Gold Member

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            I won't go as far as to say they won't fit. I can tell you that on my '74 Duster when I was running 225/60/15's with 15x7's and 4.25" of backspace with the BBP disks I didn't have a 1/4" of clearance to give up. I wasn't at factory ride height either, but I was a lot closer to it then with those wheels than I am now. So I'd say that combo with a 4" backspace definitely wouldn't have fit my car. I would suspect it wouldn't fit yours either, but body style and ride height make a big difference.
             
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