Wheel to spring clearance

Discussion in 'Tires and Wheels (Mopar Hubcaps Too)' started by Garys72Duster, Jan 8, 2019.

  1. Garys72Duster

    Garys72Duster Well-Known Member

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    Working on a 70 Dart 2 door with an A Body 8 3/4 rearend. Just wondering what is the maximum back space wheel a guy could use on this? I want to buy some 15" wheels when I get the axles re drilled to 5 on 4.5 pattern. Can I use an 8" wide rim on this ? Thinking about using Centerline wheels. Do these come with a 4" backspace? Thanks
     
  2. Steven190

    Steven190 FABO Gold Member FABO Gold Member

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    What I have found was that 15" X 8" with a back spacing of 4.5" works. As for tires a 255/60
    I had to make sure the axle was centered on the springs, so the tires would have clearance on both sides.
    Good Luck
     
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    • toolmanmike

      toolmanmike FABO Staff Staff Member FABO Gold Member

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      My 15x7's with a 4.50 backspace are real tight. I have 255-60/15's. I would say 1/2" or less clearance between the spring/tire and the same with the fender lip. You can gain a little by rolling the fender lip if you don't have wheel opening moldings. 001 50.jpg 010 (2)reduced.jpg 011 (2).jpg 040 (2).jpg
       
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      • Steven190

        Steven190 FABO Gold Member FABO Gold Member

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        With the production tolerances that had back then, plus or minus 1/4" each car is a little different.
         
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        • roccodart440

          roccodart440 Well-Known Member

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          straight edge from brake face to leafspring. deduct 1". There is your max wheel backspace.

          That will require a tire that is no more than .5" section width wider than the wheel itself.

          yes, you can use spacers for fine tuning the wheel fitment but realize that if you use a spacer you lose on the quarter panel side.
           
        • Garys72Duster

          Garys72Duster Well-Known Member

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          OK, I'm going to go and measure it now. I'm getting 5.5" inches from the wheel mount on the brake drum, to the leaf spring. Wheel mount to tire edge is 4.5 " laying flat on the floor. But on the other side with the wheel on, still have 1.5 " inches to the spring. So it looks like I can do a max backspace on the wheel of 4.5 to 5".
           
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          • toolmanmike

            toolmanmike FABO Staff Staff Member FABO Gold Member

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            Measure both sides. There is usually a difference between the two.
             
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            • roccodart440

              roccodart440 Well-Known Member

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              YES!

              That is why you always want to error on too much BS and then adjust as needed. YOu can always space, you can never move them further in
               
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              • Coyote Jack

                Coyote Jack Member #55, I'm old FABO Gold Member

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                I had 15x8 American Racing Outlaw 1's with a backspace of 4 inches. They worked perfect with 275x60-15's on a 72 Demon.

                Jack
                 
              • roccodart440

                roccodart440 Well-Known Member

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                Demon and duster vs. dart is different.
                 
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                • 69_340_GTS

                  69_340_GTS Well-Known Member

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                  4.5" backspacing it about the max on a Dart. Depending on what tire you're using it may or may not be hitting the spring. A thin spacer (1/8") might sometimes be needed. A 225 tire will fit, a 235 tire might fit, a 245 or bigger tire probably won't fit. But every car is unique. And a Duster/Demon has tons more room for tires than a Dart, so Coyote Jack's advice really doesn't apply here.
                   
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                  • TrailBeast

                    TrailBeast Slightly Twisted Member

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                    Just went through putting 9.5 with 5.5 backspacing rims on my 73 Swinger and had to move the springs in a half inch.
                    The Dart (mine anyway) has a 5.5 total distance from wheel mounting surface to the leaf springs.
                    I didn't touch the tubs and have one inch on each side of a 245/40 tire on that 9.5 rim.

                    after.jpg
                     
                  • roccodart440

                    roccodart440 Well-Known Member

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                    Really it is worth it on any abody to install offset shackles. It's easy and gives you an additional 3/4 of an inch.
                     
                  • 72bluNblu

                    72bluNblu FABO Gold Member FABO Gold Member

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                    Remember as you read through these replies that you’re technically keeping a small bolt pattern offset by redrilling your axles. So, if you listen to someone that has BBP axles about backspace you’ll probably end up with too much backspace.

                    4” on a 15x8, even on a SBP axle, isn’t enough though. 4.5” is what you’ll probably need, although on some cars you may need to adjust that with a small spacer. Especially for a 245. Everything has to be pretty much perfect to fit a 245 on a lot of the Dart body cars. Some can get away with 255’s, a few have had trouble fitting 235’s.

                    No it doesn’t. It gives you an extra 1/2”. The front spring hanger only has a 1/2” to the frame, so good luck moving it 3/4” inboard. The MP “3/4” offset kit has a 1/2” offset hanger and a 3/4” offset shackle. Puts a bind on the spring and still ends up giving you less than 3/4” additional clearance on the front half of the spring. That’s why drdiff calls his offset kit a 1/2” offset kit.
                     
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                    • roccodart440

                      roccodart440 Well-Known Member

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                      I've never actually measured. I was just going by the MPP claim.

                      I still think it's worth doing even to gain a 1/2"
                       
                    • Coyote Jack

                      Coyote Jack Member #55, I'm old FABO Gold Member

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                      Yes sorry about the post. I know the Darts have much less room than a Duster or Demon.

                      Jack
                       
                    • leblanc

                      leblanc member 2883

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                      Ever think of trying 225/70-15 on an 8'' rim?
                       
                    • Garys72Duster

                      Garys72Duster Well-Known Member

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                      That might work, too. Looking for the biggest one that will fit.
                       
                    • famous bob

                      famous bob mopar misfit

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                      thread jack here; how does a 67-8-9 barracuda fastback compare w/ the duster and dart ?
                       
                    • Coyote Jack

                      Coyote Jack Member #55, I'm old FABO Gold Member

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                      Here's a pretty good thread on that Bob. Looks like it's pretty close to the Dusters and Demons. '67-'69 Barracuda rear tire size

                      Jack
                       
                    • leblanc

                      leblanc member 2883

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                      Don't forget the Dart Sport too, this is the Demon's continuation 73-76. All 3 cars share mostly the same body except for the grills and tail panels.
                       
                    • roccodart440

                      roccodart440 Well-Known Member

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                      I run 225/50R16's on 8.5" vette wheels.

                      225 is about as small as I'd go on an 8" wheel.
                       
                    • toolmanmike

                      toolmanmike FABO Staff Staff Member FABO Gold Member

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                      tread width on 225/70's is only 6". A 8" rim would be a stretch. Literally.
                       
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                      • roccodart440

                        roccodart440 Well-Known Member

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                        yep... it's real close. The section width is just even with the outside of the wheel on a 8.5" wheel. On an 8" wheel it might be ever so slightly past it.
                         
                      • Garys72Duster

                        Garys72Duster Well-Known Member

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                        Just picked up my slicks mounted on 15" Cragar wheels. Brake drum face to spring measures 6" on the car. These wheels show 5 1/4 inches, from mount side of wheel to edge of sidewall when I measure. So I should have 3/4" to spare, right? Looks good on paper, anyway. LOL