Author Topic: 12 bolt backing plates  (Read 2474 times)

SS396

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12 bolt backing plates
« on: August 29, 2011, 08:55:01 PM »
Does anybody know who sells  repo backing plates for a 68 12 bolt that is close to original as in appearance and thickness. Even better is it still possible to buy GM ones anywhere? Mine are badly rusted and beyond salvage.

1967RS/SS

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Re: 12 bolt backing plates
« Reply #1 on: August 29, 2011, 11:54:47 PM »
Don't know about the quality of their backing plates, but inline tube sells new ones.  I asked about their rear drum brake kit and the said there stuff is made in the USA.  Maybe an option???
1967 RS/SS L-48
Van Nuys 01C
Joe

mopar346

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Re: 12 bolt backing plates
« Reply #2 on: September 01, 2011, 12:09:57 AM »
I believe 10 bolt stuff swap over, I am not sure if they are identical though.

L78 steve

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Re: 12 bolt backing plates
« Reply #3 on: September 02, 2011, 02:33:38 PM »
10 bolt plates are identical.
69 Z/28 Dover White X33,ZL2,PS,M20,Std.int.04C
67 SS/RS Mt. Green 1W,2LGSR,3SL,4K,5BY,07C
70 Nova L78 Blk. Cherry,Sandalwood,M21,02B

BlackoutSteve

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Re: 12 bolt backing plates
« Reply #4 on: November 27, 2012, 02:23:33 AM »
Found this on-topic thread in a search.. :)

Also regarding the backing plates..
I aquired a used pair that have splash shields welded to them. I didn't know splash shields were ever added to drum backing plates and thought someone must have once added them. I was also considering removing them until I did a short Google search and found some with..

The afore mention In-Line Tube website has the option of with and without..
http://inlinetube.com/Drum%20Brakes/Drum%20Brakes.htm



Question: Where the shielded plates ever a Camaro option, standard or never available on them? If not, what were these normally fitted to?

Also, looking at the ones that I have that came off a 68 Camaro (no idea if original to the car), were the welds normally that rough? This is mainly why I assumed a back-yard welder had added them.

Restoring my RHD 69 Jane in Melbourne, Australia.
http://www.usmuscle.com.au/Forum/showthread.php?t=2840

BlackoutSteve

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Re: 12 bolt backing plates
« Reply #5 on: November 27, 2012, 02:32:09 AM »
Also, there are two different bore sizes for rear wheel cylinders available for rear drums.. 7/8" and 15/16"..

Was only one size available on 1st Gens, or were both sizes used depending on the application?
Thanks

z28rich

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Re: 12 bolt backing plates
« Reply #6 on: November 27, 2012, 05:12:00 AM »
Found this on-topic thread in a search.. :)

Also regarding the backing plates..
I aquired a used pair that have splash shields welded to them. I didn't know splash shields were ever added to drum backing plates and thought someone must have once added them. I was also considering removing them until I did a short Google search and found some with..

The afore mention In-Line Tube website has the option of with and without..
http://inlinetube.com/Drum%20Brakes/Drum%20Brakes.htm



Question: Where the shielded plates ever a Camaro option, standard or never available on them? If not, what were these normally fitted to?

Also, looking at the ones that I have that came off a 68 Camaro (no idea if original to the car), were the welds normally that rough? This is mainly why I assumed a back-yard welder had added them.




those were added.

69Z28-RS

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Re: 12 bolt backing plates
« Reply #7 on: November 27, 2012, 05:36:59 AM »
One can tell that isn't a factory weld....  looks more like my welding....  LOL....
Gary W / 09C 69Z28-RS, 72 B 720 cowl console rosewood tint
69 Corvette convertible, silver/black 350 hp,
60 Corvette white/red, 72 Corvette coupe, '70 Mach I 
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BlackoutSteve

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Re: 12 bolt backing plates
« Reply #8 on: November 27, 2012, 07:48:31 AM »
Thanks, then I guess I was right to question them..  :P

Any idea what bore size is correct re: the wheel cylinders?

KurtS

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Re: 12 bolt backing plates
« Reply #9 on: November 27, 2012, 07:17:57 PM »
That's a lot of work to find the right arc of metal to weld into place. Lots of factory welds aren't pretty, look at the subframe. :)
Not to say these are original, but I've seen these used somewhere before - maybe on later cars?
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william

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Re: 12 bolt backing plates
« Reply #10 on: November 27, 2012, 11:38:55 PM »
GM serviced 1st gen backing plates well into the '90s but the part numbers changed. They are in group 5.001 if someone has a P & A manual from that period. Maybe had other applications and could still be available.

BlackoutSteve

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Re: 12 bolt backing plates
« Reply #11 on: November 28, 2012, 06:33:13 AM »
That's a lot of work to find the right arc of metal to weld into place. Lots of factory welds aren't pretty, look at the subframe. :)
Not to say these are original, but I've seen these used somewhere before - maybe on later cars?

My thought exactly Kurt.. Appearance of the subframe welds and the effort to cut out the shape of the shield.. Hmmm..
Thanks William. I didn't see any numbers stamped on them and after stripping the paint, they appeared to have been sand blasted at one point.

69Z28-RS

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Re: 12 bolt backing plates
« Reply #12 on: November 29, 2012, 02:14:15 AM »
a factory frame weld may have welding flash, etc, but they generally aren't ground off as in the photos of that backing plate.  I suspect some one took those plates off another backing plate, and welding them to their factory backing plates, then ground off their 'welding ugly'..  :)

hotrod68

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Re: 12 bolt backing plates
« Reply #13 on: November 29, 2012, 03:50:12 AM »
   10-bolt plates will work, but you may have to grind the center axle bearing holes oversize a tad. I have a new Moser 12-bolt under my car and I used the backing plates from an old 10-bolt. I don't know of the Moser axle bearings are bigger than standard GM or not because I used C-clip eliminators. But the holes only need to be enlarged slightly. I used a carbide bit in a grinder and it's a snap. Hope this helps.

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68camaroz28

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Re: 12 bolt backing plates
« Reply #14 on: November 29, 2012, 05:04:02 AM »
Will look for a better pic but here is one of our 68's rear backing plates and other than a normal clean & prepare for paint (no grinding) its untouched.
Chick
68 Z/28 NOR 01B Orig motor/trans/rear
69 Z/28 NOR 07A Orig Block & GM Cross-ram/carbs
69 L34 Rest. Nova Father/Son Car
69 L78 Surv Nova Purch 4/69 31K miles
67 L89 Corv Tribute
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R 68Z build- http://www.camaros.net/forums/showthread.php?t=182584