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61 Hawk rear finned brake drum

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  • Brakes: 61 Hawk rear finned brake drum

    Hello, fairly early on in the resto of my 61 Hawk, I organised all the brakes to be re- done, all 4 drums got machined, the brake guy said one was warped , so I took over a spare I had. The spare one was good, & machined up ok, but it didn’t have the studs & hub pressed in, I thought he would do that on pick-up, but he said I’m better off putting on the wheel & the nuts & wheel will press it on. Anyway, that didn’t work. Around the stud holes on the drum, there is a bit of protruding if that’s the right word, where it goes over the stud flanges. Question is, is it saveable if I get the hub back off & get it properly pressed back on, will the drum centre with the stud holes have to be flattened out. The way it is now, it doesn’t spin true & fowls on the backing plate. Or look for another complete drum & hub, regards Cus
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  • #2
    Been there - done that, and your dilemma sounds all too familiar. (I assume you are talking about a rear drum?) Sounds like your machinist is blessed with a machine that turns drums, both on and off the hub. Those machines and adapters are getting hard to find.

    But you also need a competent machinist. If his advice was to mount the drum on the hub by using the lug nuts to force it on, I seriously question his competency. Giving him the benefit of doubt, possibly he did not inspect the hub, so was unaware of the swaged studs. As is, your drum is still likely salvageable, just place a heavy metal block against the back side, flat against the surface, then use a small hammer to ping the 'protruding' surface back down flat. You will then still be faced with how to push the drums onto the still swaged studs. Swage is sorta like brading; the studs are mushroomed against the drum, to capture it permanently in place against the hub. Swaging is not necessary, since the wheel, with torqued lug nuts, will hold the drum in place, and the stud shoulders will keep it centered.

    So, before attempting to remount the drum onto the hub, you first need to remove the swage (beaded, mushroomed area) from the studs. You could use a file, if you have lots of time and patience. Or you can use a 5/8", good quality hole saw ( I use LENOX), which has an ID that perfectly slips over the stud, to keep it on center and shave the swage away. Be careful, use a drill with variable trigger and go slow, since the metal is softer than you'd think, and you will cut the swage away in a few seconds. Be careful to stop at the swage, and do not cut the shoulder off the stud, or else you'll need to replace the stud(s). With the swages removed, the drum will slip right onto the hub, all the way home against the hub surface. If you don't wanna cut the swages, or goof up in doing so, just install all new studs. But you'll have to press them out/in, and cutting the swage is much easier.

    The next obstacle you may face: some hub & drum assemblies, from the factory, were not centered, so (I believe) the drum brake surface was machined to bring it into spec as an assembly. I was astonished to find this out, till I found out Moser made the same mistake with the first few flagged axles they made for our vendors around 2005. You can check it easy enough, once the drum is mounted, by adjusting the shoes out till they are dragging against the drum, but you can still turn the drum by hand. Rotate the drum slowly and feel for high/low spots. To do this without the tire/wheel mounted, turn the lug nuts around backward and tighten them against the drum.

    As for the drum kissing the backplate lip, sometimes that is due to the axle end play spacers on the wrong side (should be on passenger side), especially if it is occurring on the driver's side. Sometimes you can alleviate it by simply swapping drums, left to right. Sometimes it is due to worn hub taper and/or worn axle taper, allowing the hub/drum to slip too far onto the axle. Regardless, if all else fails, you can simply grind the lip of the back plate, and/or the lip inside the drum. Just be careful, and a handheld grinder will do the job in short order, but only take a little off at a time. First, determine exactly where it is rubbing, by looking for shiny spots. You may even need to drive the car a bit in order to get it to wear the shiny spots enough to see easily; it will also become audible when driving, especially in left or right turns. If driving, note whether it is more pronounced in left or right turns, since that will help determine which side it is coming from.

    Good luck, and I hope this helps.
    Joe H
    Last edited by JoeHall; 02-23-2021, 05:27 PM.

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    • #3
      Hello Joe,
      Amazing advice, many thanks, I'll give it a go & report back,

      regards, Cus
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      • #4
        After a closer inspection & running the drum all bolted down, with the car on axle stands, I can see that the drum is out, so I've ordered a new drum & studs & will have
        it properly pressed with the studs going through to the drum as per original. I also noticed the hub was not that true while spinning, I have a spare which seemed to be better,
        Not bad, one out of 4, the other 3 are fine, & very happy with braking at this stage.

        regards, Cus
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