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10" Brake drums on 9" Ford rear with GM axles

Discussion in 'The Hokey Ass Message Board' started by chizzy, Mar 1, 2013.

  1. chizzy
    Joined: May 14, 2009
    Posts: 5

    chizzy
    Member
    from Waxhaw, NC

    Ok, so I have 9" Ford rear in my '55 Chevy running 10" Ford drums with GM 4-3/4" bolt pattern (the previous owner did a pretty lousy job of drilling out the old drums). Drums are shot and need replaced, but I've been unable to find replacements. I was considering having new 10" Ford drums re-drilled at a machine shop to match the GM bolt pattern, but not sure the best way to accomplish that, or maybe someone can point me in the right direction for a new set. Any help would be appreciated.:confused:
     
  2. 95% sure that you neef ford drums and they need to be drilled to match
     
  3. classic gary
    Joined: Sep 24, 2009
    Posts: 504

    classic gary
    Member

    Well the difference is only 1/8" "per side", so just drill the existing holes 1/8" larger.......
    You are going to need to use ford drums for the center hole fitment, and brake shoe fit.
     
  4. bigEkustoms
    Joined: Jan 21, 2009
    Posts: 105

    bigEkustoms
    Member

    I would have a machine shop drill the chevy bolt pattern on new ford drums. Having the correct size and spacing is critical to the correct operation of the drums. Please update with some pictures and machine shop you used for us guys in the Charlotte area. E
     

  5. Easy to do yourself, its just math. Take dial calipers, scribe out a circle for the bolt pattern you need, mark the first hole, than mic out your distance center to center of your lug studs, and mark the drum. If you are equal distance on your scribed line to all 5 holes, you did it right and start drilling.
     
  6. I'm doing the same - 9", custom axles for Chevy 5x4 3/4 pattern. I plan on running drums and my current idea is something I read elsewhere. I have the ford backing plates and I can get Chevy ones. The idea is to cut out the ford center and weld it into the Chevy backing plate.....then I can use the Chevy brakes and drums and not have to drill holes and "weaken" the drum by having 10 holes in a 4 1/2 to 4 3/4 circle....

    Or should I just go with Ford brakes and redrill the drums for the Chevy pattern? Is that strong enough?

    Thoughts?
     
    Last edited: Dec 21, 2014
  7. A 1/8 larger hole will only give 1/16 "per side" increase in the bolt circle.
     
  8. squirrel
    Joined: Sep 23, 2004
    Posts: 55,942

    squirrel
    Member

    I have a big bearing early 9" in my Chevy II, with the early Ford 11" backing plates, custom 31 spline axles, and Chevy 11x2" drums, and the Chevy bolt pattern for the wheels. The only tricky part was ordering the axles, getting dimensions just right.
     
  9. Ddooce
    Joined: Oct 27, 2010
    Posts: 132

    Ddooce
    Member
    from Memphis Tn

    Rotten Leonards make a really useful jig to redrill drums and axle shafts - and they are Alliance suppliers
     
  10. Andy
    Joined: Nov 17, 2002
    Posts: 5,117

    Andy
    Member

    The axle is drilled and the drum will pilot on the axle. The holes do not need to be perfect. Drill them the best you can and file as required. Drums are often loose on the studs.
     

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