Disc brake conversion wheel hub sizing

Brakes for your Classic Mopar

  1. ChuckDock

    ChuckDock Well-Known Member

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    I have a 67 Barracuda. It has the 10 inch drums front and back. I'm looking at all the options out the to convert to a disc setup. Wilwood, Scarebird, Dr. Diff, Piratejack, oem 73+...omg

    I have aftermarket steel wheels with a hub size of 2 3/8.
    Do any of the kits going to disc allow for such a small hub size opening?

    I really rather not go to the bigger anything because I just got done doing uca offset bushings, lca bushings, new upper and lower ball joints (and more, new t-bars and sway bar). Just got done meaning the car is still on the lift with the brand new parts I just installed. Plus my wheels look good and tires are new.
     
  2. MoparLeo

    MoparLeo NRA PATRON LEVEL LIFE MEMBER

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  3. 72bluNblu

    72bluNblu FABO Gold Member FABO Gold Member

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    I don’t think you’ll have any luck finding a disk hub to fit a 2 3/8” wheel hub bore.

    The stock 73+ disks have a hub that’s about 2.6” to 2.7” in diameter, that does depend a little on who manufactures the disk. The DoctorDiff aluminum hubs have a base diameter of 2.7”. The current Wilwood kit for 10” drum spindles have a gigantic hub, it’s 3.24” at the base (!!!).

    I don’t know about the scarebird kits. The PirateJack kits are just 73+ disks, but the small bolt pattern kits do have the hub diameter machined down to work with earlier rims. I doubt they’re turned down to 2 3/8” though. The wall thickness of the rotor hub at the outer bearing is ~.3175, and the disk I have measures ~2.6” out there. Cutting that down to 2 3/8” would mean a wall thickness of .205” at the outer bearing, that’s like a 35% reduction.

    When I spoke with DoctorDiff about the hub diameter on his kit he seemed to think turning them down to 2.5” would be ok, although I didn’t want to cut that much. I ended up having my wheels machined instead, but they’re aluminum and don’t have the rolled shoulder that steel rims have. That’s not an option for you.
     
    Last edited: Apr 15, 2019
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    • RedFish

      RedFish Well-Known Member

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      I just measured 75 model a-body disc hub to be right at 2.78 inches.
      I'm thinking since the wheels you have do fit your drum brakes spindles hub, keeping those spindles with disc brakes, like scarebird does, may be the only option.
       
    • ChuckDock

      ChuckDock Well-Known Member

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      Ah, so thats what I was wonder about when I looked at scarebirds rotors, there are no hubs in them. So I would just re-use mine, which is fine by me except my drums are a miss match. One drum has the separate hub, when the other drum has the hub fixed to it. I looked on Rockauto and other part stores but don't see where I could purchase another hub, but have to believe they are out there. Maybe scarebird has some as well..
      Thanks all for the replies! Maybe there is hope after all.
       
    • ChuckDock

      ChuckDock Well-Known Member

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    • plumkrazee70

      plumkrazee70 FABO Gold Member FABO Gold Member

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      Scarebird isn't going to have the hubs. They recommend that you separate the drum
      from the Hub and press in new studs.

      Look at you hub/drum on the drum side, where the
      studs come through. If they are still "swedged" together, that will need to be removed and the assembly will separate.

      I've read using a 5/8 hole saw to cut the swedge.

      I have scarebird brakes on the front of mine and it all works well together, just be sure to get quality calipers (Napa).
       
    • ChuckDock

      ChuckDock Well-Known Member

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      I've been doing a bunch of googling and it really looks like those hubs are not made or available anymore which is a bummer. Yup, I've been reading posts on how to separate the hub from the drum, doesn't seem to bad.
      It's just, what do you do when the hub eventually goes bad?
       
    • plumkrazee70

      plumkrazee70 FABO Gold Member FABO Gold Member

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      Unless it gets damaged in some way, I'm not sure it ever go bad. The bearings and races are replaceable and are available.
       
    • RedFish

      RedFish Well-Known Member

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      Hub failures are bearing spinning inside the hub ruining the bore or lug stud spinning in the hole. Dorman did offer these 7/16 studs with oversized splines so a spinning stud was repairable. I don't know if still available. Scarebird requires longer studs anyway. I don't know if those will be 7/16 or 1/2 and I don't know if your wheels accept 1/2 inch studs. 1/2 inch lug nut will require a different lug wrench.
      Good used hubs for the 9 inch or the 10 inch drum assemblies are usually found through "parts wanted" here.
       
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