Gen 1 Viper brakes reimagined

Brakes for your Classic Mopar

  1. racerjoe

    racerjoe Well-Known Member

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    I bought some Gen 1 Viper caliper years ago with intentions of using the Dr. Diff kit. I ended up putting the car back together with the FMJ 10.95" discs I had just to speed up getting the car back on the road. Now that the car is back together and has about 1500 miles of getting new build bugs worked out, it's time to start upgrading things. I decided against using the Dr. Diff kit and make my own.
    My first course of action was to measure the arc on the caliper to determine the maximum diameter rotor that could fit in the caliper. I wasn't able to get an exact measurement since the top of the caliper is open, but I got it close enough. By the magic of geomtery, I determined a rotor diamter of 13.25-13.5 would work. After way too much time researching rotor diamters on rock auto, I decided to start with a 13.25" modern mustang rotor as a test piece.
    Before I could test the rotor, I bought some 10.95" rotors and had a friend turn them down into hubs. I picked these up from rock auto for $25/ea.
    hubs 3.jpg hubs.jpg

    My calculations to determine the maximum rotor diamter appear to be close.

    rotor with caliper.jpg

    all of this looks great, until I figure out my wheel won't fit. The spokes hit the caliper... bummer. At this point I went back to searching for another rotor with a higher offset between the brake surface and the wheel mounting surface. During a convestation with another member on here, he recommneded I look at the 2010 Challenger RT rotor. This rotor. The offset on the challenger rotor was about .25" greater than the mustang rotor, and the diamter was slightly larger at 13.6" It looked like it would work, so I moved forward with designing a bracket.
    Since the car already had the FMJ spindle, I figured it would be easiest to design a bracket using those spindles instead of a drum spindle. After some measuring and cutting 3 different samples, I arrived at this:

    rotor.jpg

    It's a very simple design and would require about 1/4-3/8" worth of spacers between the bracket and the caliper. It was hard to determine exactly how much since the wood crushes when tightening. The wheel fit too, but would likely require a 3mm spacer for some piece of mind.
    wheel.jpg

    And why not compare the difference..

    comparisson.jpg

    I had a buddy convert my hand drawings into CAD and I sent the file to sendcutsend.com. I was amazed at their customer service. If you need anything laser cut and don't want to deal with the minimum quantities many local companies have, I suggest this company. They were great!
    Caliper bracket 2.jpg caliper bracket.jpg

    Test fitting everything with the new brackets:

    1.jpg 6.jpg

    Turns out a 3/8" spacer would be perfect.

    At this point, having a wheel spacer was really buggin me. For some reason, I decided to look at the rear rotor on a 2010 Challenger SRT. It has a really high offset, almost 1/2 more than the RT front rotor. This was good. The diamter did get slightly bigger again, up to 13.7". I figured I'd give it a try, so I picked up a rear SRT rotor locally even though I was apprehensive about the diameter exceeding what I thought would be the maximum for this caliper.
     
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    • racerjoe

      racerjoe Well-Known Member

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      The first thing I checked was the pad on the brake surface. It seemed to be fine. Rev3 e.jpg

      Since the offset was greater, and I had a 3/8" spacer between the bracket and the caliper already, I was excited to think this could go together with no spacers, or at least very thin spacers. I also wasn't sure if it everything would bolt up with the bracket I had made since the diamter grew. Turns out it did, but with only .010" between the caliper and the edge of the rotor.

      rev3 b.jpg rev3 c.jpg rev3 d.jpg rev3 d.jpg

      The only spacer required is a .100" washer between the bracket and the spindle.

      Now I have about 1/2" between the wheel and the caliper. I didn't measure, because it's plenty!

      Rev3 - Copy.jpg rev3 a.jpg

      I'm having another bracket cut to accomodate the larger diameter rotor and everything should be perfect. The only bad part to this is the wheel studs kinda broke the budget aspect of this project. I needed a stud with a large shoulder and the only ones I could find were $75 for 5. So now I'm into the hubs for $300, which is what the aluminum ones from Dr. Diff cost. In the end, I don't mind because I didn't enter this project to be 100% budget, but I also didn't want to buy a $2K brembo, or bear kit.

      rotor 2.jpg studs.jpg

      I have a Powerstop drilled and slotted rotors on the rear, so I'll purchase the matching set for the front. I also need to get some new front brake hoses. I'll post more updates as I get part installed.
       
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      • rumblefish360

        rumblefish360 I have escaped the evil Empire State! FABO Gold Member

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        Nice reimagining work! Now it’s time to get to work on mass production of brackets and parts and make some money!
         
      • Kendog 170

        Kendog 170 Let the boy go !

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        What size rim are you using?
         
      • racerjoe

        racerjoe Well-Known Member

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        They are Rocket Racing, Rocket Attack 18x8 with 5.5" backspace.
         
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        • racerjoe

          racerjoe Well-Known Member

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          Nah, I'll be happy to share the drawing when it's 100% confirmed.
           
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          • Needswork

            Needswork Well-Known Member

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            Great work! Thanks for sharing the info.
             
          • gzig5

            gzig5 Well-Known Member

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            Good job. That gives me a few ideas for my project. Love the wood mockup. By using the spacer washers, you could make the brackets on a drill press. The position of the holes is not overly critical. Wouldn't take much to do it on a manual milling machine from thicker material and eliminate the loose shims either.
            I was under the impression that Dr. Diff wouldn't sell the aluminum hubs by themselves, only with the kit?
             
          • racerjoe

            racerjoe Well-Known Member

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            I'd say the hole locations are critical if you want a nice tight bolt fit up. I don't see why you couldn't do on a drill press if you were precise with your measuring/centerpunching, etc. Fortunately, the spread on the spindle and the caliper are a nice round number. 3-1/8" on the spindle, and 100mm on the caliper. The measurement that took a few tries to get correct was the spread apart. I didn't have an accurate way to measure it, so it took some trial and error with the wood block. If you have a milling machine, you could certainly make it as you described. I don't have one. Honestly, .100" washer isn't a big deal. My understanding is most of the high end aftermarket brake kits require shimming to get the caliper centered on the rotor. Essentially, that's what that .100" shim is doing.
            Dr. Diff does sell the hubs. I don't know how they compare in terms of location of wheel mounting surface. Meaning, does he make the surface 1/4" further back so the wheel is in the factory position once the rotor is on there?

            FYI. Sendcutsend.com only charged $39 total to have these brackets cut. That's hardly worth the time to cut this out of 1/2" plate by hand.
             
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            • gzig5

              gzig5 Well-Known Member

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              I guess tolerances are relative, depending on what you are working on. I agree, that you don't want a lot of slop in the holes and would prefer minimum clearance. 0.005-.010" accuracy on the hole placement would probably give what is needed to make it work and should be achievable by a someone who understands how to use a layout and drill accurate hole with a press. A Bridgeport would be a slam dunk. By contrast, the project I'm currently dealing with at work has tolerance requirements of less than 0.001"for relative hole location accuracy, and that probably tainted my original comment. Regardless, I think you did a great job, and appreciate your efforts as they make it easier for those of us that follow.
               
            • racerjoe

              racerjoe Well-Known Member

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              Haha! Completely understood. I've worked with machinists in the past. They have a different way of thinking when it comes to tolerances.
               
            • DionR

              DionR Well-Known Member

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              I could be wrong, but I think the surface is actually further out. Pretty sure @72bluNblu has said the kit he uses increased the front track some.
               
            • 72bluNblu

              72bluNblu FABO Gold Member FABO Gold Member

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              I think the hub is basically the same as if you would turn the rotors off a stock rotor/hub. The addition of the floating rotor onto the hub widens the track width. So the aluminum hubs have the outer face of the hub in the same place as stock, so the thickness of the floating rotor is added.

              I know that with DoctorDiff’s 13” cobra kit about 3/16” is added to the 73+ factory track width. Which is about the thickness of the rotors at the hub face.
               
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              • DionR

                DionR Well-Known Member

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                Interesting. Thanks for clarifying it.
                 
              • 72bluNblu

                72bluNblu FABO Gold Member FABO Gold Member

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                I haven’t measured the hubs to be 100% sure. But 3/16” is pretty much exactly the thickness of the floating rotors used with the 13” kit on my Duster. So it has to be pretty close to the same.
                 
              • DionR

                DionR Well-Known Member

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                Makes sense.

                I am assuming the additional 3/16" of track width is per side?
                 
              • 72bluNblu

                72bluNblu FABO Gold Member FABO Gold Member

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                Yup, 3/16” per side. So I just add about +5mm of offset to the rims compared to what you’d use for 73+ disks.
                 
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                • DoctorDiff

                  DoctorDiff Well-Known Member

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                  You are correct.

                  Due to the thickness of the rotors, rear disc brakes also increase the track width 1/8" per side.
                   
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                  • DionR

                    DionR Well-Known Member

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                    I was pretty sure Andy moved the face of the hub around, but had no clue where your’s were. Seemed like there was overlap between you guys, but had no idea how much. Thanks for confirming the info.
                     
                  • racerjoe

                    racerjoe Well-Known Member

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                    Finally getting around to finishing up this conversion on my car. I have some brake lines to finish up, so nothing to report yet on performance gains. 1FA0924B-1117-40A3-9D5D-E854D82041CA.jpeg B6BAEEAC-6FDB-4276-932C-64900BC95D45.jpeg 776F507B-078C-4D3E-92A7-920121442DB5.jpeg D8E57247-E9FF-4568-93F6-4832D0CC8129.jpeg 4374B70A-A82B-45C7-8F26-136A4694F009.jpeg FE6D27EA-727D-4A11-8414-1D701E537813.jpeg FC555140-1BA2-4D9B-BAA1-2E6A05DB6A90.jpeg 254C7F2F-5680-41B4-9F1A-270398956B0C.jpeg 9A29831F-47B3-4DAD-A3BB-C0C02AAEB79E.jpeg
                     
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