Duster - Suspension/Wheel/Tire Combo Question

Tires and Wheels (Mopar Hubcaps Too)

  1. Wilson340

    Wilson340 Well-Known Member

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    I need help in determining if the following wheel and tire set up will fit under my stock 73' Duster rear fender and not rub against the stock located CalTrac leaf suspension. Any help would be appreciated. My concern is that the 4.875 backspacing might be too much and cause it rub against the leaf springs. Thank you.

    Wheels: Centerline 15x8.5" with a 4.875 Backspacing
    Tires: P275/60r15
     
  2. 72bluNblu

    72bluNblu FABO Gold Member FABO Gold Member

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    Depends entirely on what rear axle you have. If it's a BBP 7.25 or an 8.25, it won't fit. Not even close.

    If it's an 8 3/4 with BBP axles it will probably be too close to run on the street without some rubbing, but a small spacer (1/8") would probably be enough to clear them.
     
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    • Wilson340

      Wilson340 Well-Known Member

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      Thank you for the feed back. I have a 8 3/4 with a SBP. I'll have to look into spacers. Any real safety issues with running that small of spacer?
       
    • 72bluNblu

      72bluNblu FABO Gold Member FABO Gold Member

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      There are no real issues running small spacers (1/4" or less) as long as you have the proper thread engagement on the studs/lug nuts. There are arguments for having hub centric spacers vs being lug centric, but quite frankly many cars and wheels are lug centric.

      But, to address your bigger issue- SBP axles change your clearance. SBP axles have less flange offset, which means you won't need a small spacer. You'll need a spacer that's at least .375" if not larger, and that's more than I'd run. I generally draw the line around a 1/4" spacer.
       
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      • crackedback

        crackedback FABO Gold Member FABO Gold Member

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        According to a spreadsheet that I did years ago, with an 8.5" wheel, 4.81" backspace centers the it up in the wheel well.


        That's stock SBP 8.75 std length

        Not having the spring moved and a 275 tire is going to be a tight fit no matter what.
         
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        • 72bluNblu

          72bluNblu FABO Gold Member FABO Gold Member

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          I think it’ll be tough with the SBP axles with that much backspace.

          But, to be completely fair I’ve converted all of my cars to BBP before I’ve maxed out the tires/rims. So I don’t have as much hands on with the SBP clearances. I’m using measurements on the SBP axles to convert what I know works with BBP to a recommendation for SBP, so there’s more room for error.

          275’s are a pretty tight fit, so taking measurements on your own car is definitely the best policy as not all of these cars were identical. A 1/4” either way isn’t uncommon, and that makes a big difference when you get down to the minimum clearances which is what happens with 275’s.
           
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          • Wilson340

            Wilson340 Well-Known Member

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            Thank you. I appreciate all the input.
             
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            • DemonK9

              DemonK9 FABO Gold Member FABO Gold Member

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              '73 Duster, cloned to a '71 (tail panel, front clip), 7 1/4 rear end: You can fit 295/50/15 on the rear, as pictured here. Not sure of the backspacing that the rims had though. Tires would only rub if they bottomed out going up into the curve of the fender well (if you get what I am meaning to say...lol). Had air shocks on rear to stiffin' it in the rear to prevent it from bottoming out on bumps with a load (2 people) in back.......so, you can fit up to a 295 with minimum rub issues.

              backedit.jpg
               
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              • 89on35s

                89on35s Inferno Red Duster FABO Gold Member

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                I have a 74 Duster with exactly that wheel and tire (Centerline 15x8.5" with a 4.875 Backspacing and 275-60-15 Mickey Thompson drag radials). It has an A body 8.75 rear with a big bolt pattern conversion. That tire on that rim fits perfectly for me. I have uncut fenders and stock location super stock springs.

                I know the big bolt pattern conversion adds a bit of width but I forget how much. I'm sure a small spacer will set it right for you! I wish I took better photos of that clearance I have.

                Cley
                20190718_161345.jpg 20190718_161904.jpg
                 
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                • famous bob

                  famous bob mopar misfit FABO Gold Member

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                  Dont fret I`m running about 9/16" spacers w/ 295 60 d15 treaded slicks on the street , I do have full engagement of aftermarket 3" long studs tho.

                  thumbnail.jpg
                   
                • Demonic

                  Demonic Well-Known Member

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                  Nice look with the Hurst and Duster emblem! Very cool. :thumbsup:
                   
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                  • 72bluNblu

                    72bluNblu FABO Gold Member FABO Gold Member

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                    Only with the rear end jacked up in the air like yours is. And, if it rubs over bumps, or loaded, or going around a corner it means the wheels don't fit. Wheels that fit don't rub.

                    I run a 295/35/18 on the back of my Duster as well, but my car is lowered so the wheels actually have to fit inside the wheel wells. It takes a 1/2" spring offset and another 1/2" trimmed off the quarter lips to do it, and even then barely. Sure, if you run air shocks and destroy your shock mounts you can run darn near anything. Doesn't matter if they hang a 1/2" out of the wheel wells if the back of the car is 3' in the air.

                    The BBP conversion adds between 5/16" to 3/8" to each side, which is a decently big spacer to run. It looks like your wheels are nicely inside the wheel wells (good job!), which means they're also fairly close to the springs. Which also means the OP will have to make up all of that space with a spacer. Personally I don't like to use spacers that are more than a 1/4" on the street. Obviously they make larger spacers than that and people run them, but that's the rule of thumb that I use.

                    And your wheels hang a good 1/2" outside the quarter lip too. If your car was anywhere near stock ride height those tires would rub like crazy. But it's closer to '70's street freak height than it is to stock.

                    295's do not fit on a stock Duster. 1/2" offset and some quarter lip trimming is the only way to get them to fit. Anything else depends on the wheels hanging outside the quarters and the ride height more closely resembling a 4x4 than a car.
                     
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                    • dave225

                      dave225 Active Member

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                      Why wouldn't you jack the car up and measure it to be sure?
                       
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