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-   -   12 Bolt Drum Brake Upgrade (https://67-72chevytrucks.com/vboard/showthread.php?t=692672)

aggie91 01-15-2016 11:43 AM
Re: 12 Bolt Drum Brake Upgrade
 
Quote:
Originally Posted by jjzepplin (Post 7448493)
So I guess the backing plates are offset more to the inside and the shoes are 3/4" wider as well as the drums?
Yes. Does not change the overall width of the axle.

aotte1 01-24-2016 08:11 PM
Re: 12 Bolt Drum Brake Upgrade
 
5 Attachment(s)
Karl,

Finally got the side by side photos, took me forever to get the work bench cleaned off!!! Let me know if more photos will help.
The '79 brake shoes are on the left and the '77 brake shoes are on the right. The lining material area is the same on both. The size specification are the same for both. They do have different part numbers. The brake shoe frames are made a little different, however, both sets of shoes, mounting hardware and emergency brake fit the '77 backing plate. The '79 brake shoe frame is a little thicker then the '77. The '77 frame has double material at the top, which you can see in later photos. The holes in the frames are also a little different, however, those used for this application are the same - so no matter. Also, more information is provided in above posts.

Les

aotte1 01-24-2016 08:34 PM
Re: 12 Bolt Drum Brake Upgrade
 
4 Attachment(s)
A few more photos. In the second photo you can see additional material added at the top of the '77 brake shoes. Photo three shoes the '79 without this additional layer, however, the frame material is thicker then the '77.

Les



Attachment 1491513

Attachment 1491514

Attachment 1491516

aggie91 01-25-2016 12:57 PM
Re: 12 Bolt Drum Brake Upgrade
 
That's what I thought was the difference between the years. So, the later model shoes will work and fit in place of the 76-77 shoes with no issues. It appeared to be a manufacturing/engineering change to the frame and not to the actual lining. The frame change on the shoe would have made them quicker and less expensive to produce those parts.

aotte1 01-25-2016 10:54 PM
Re: 12 Bolt Drum Brake Upgrade
 
O
Quote:
That's what I thought was the difference between the years. So, the later model shoes will work and fit in place of the 76-77 shoes with no issues. It appeared to be a manufacturing/engineering change to the frame and not to the actual lining. The frame change on the shoe would have made them quicker and less expensive to produce those parts.
Yes, that is correct, from what I can see.

Note: The brake drums for this application are a LOT bigger, then the smaller two inch ones that came on the '65 12 bolt.

Les

TheFix 07-14-2016 06:53 PM
Re: 12 Bolt Drum Brake Upgrade
 
Going to dredge up an older thread here, but I was wondering where someone could buy the backing plates? I can get every part from the auto store, except the backing plates. Any info is appreciated.

aotte1 07-14-2016 11:48 PM
Re: 12 Bolt Drum Brake Upgrade
 
Not sure if new ones are available? Lots of them should be available on trucks, subs and blazers being parted out with 12 bolt rears. Also, could post a WTB request in the parts section. Not sure when first used, '77 to '87 trucks and '91 subs/ blazer could have them. A key way to identify vehicles, that have these backing plates is to look for 1 1/4 inch wide front rotors, they are the JB5 brake package.

Hope this helps,
Les

SCOTI 07-15-2016 12:22 PM
Re: 12 Bolt Drum Brake Upgrade
 
Quote:
Originally Posted by aotte1 (Post 7653660)
Not sure if new ones are available? Lots of them should be available on trucks, subs and blazers being parted out with 12 bolt rears. Also, could post a WTB request in the parts section. Not sure when first used, '77 to '87 trucks and '91 subs/ blazer could have them. A key way to identify vehicles, that have these backing plates is to look for 1 1/4 inch wide front rotors, they are the JB5 brake package.

Hope this helps,
Les
If you're in a wrecking yard, the easy way to spot the HD brake option is the much larger/wider drums when peeking under the vehicle.

TheFix 07-15-2016 12:55 PM
Re: 12 Bolt Drum Brake Upgrade
 
Quote:
Originally Posted by aotte1 (Post 7653660)
Not sure if new ones are available? Lots of them should be available on trucks, subs and blazers being parted out with 12 bolt rears. Also, could post a WTB request in the parts section. Not sure when first used, '77 to '87 trucks and '91 subs/ blazer could have them. A key way to identify vehicles, that have these backing plates is to look for 1 1/4 inch wide front rotors, they are the JB5 brake package.

Hope this helps,
Les
Quote:
Originally Posted by SCOTI (Post 7654097)
If you're in a wrecking yard, the easy way to spot the HD brake option is the much larger/wider drums when peeking under the vehicle.
Thank you for the information.

ratty69 08-01-2016 08:03 PM
Re: 12 Bolt Drum Brake Upgrade
 
So just to confirm that these will work on pre-70.5 (narrow axle) trucks as well? I have searched and googled and know they WILL work with anything 70.5-87 (wide axle). Can't find anything confirming fitment on narrow axles.

I have an 87 Blazer setup I'd like to install on my 69.

Thanks in advance.

racecougar 08-02-2016 10:21 AM
Re: 12 Bolt Drum Brake Upgrade
 
Quote:
Originally Posted by ratty69 (Post 7671204)
So just to confirm that these will work on pre-70.5 (narrow axle) trucks as well? I have searched and googled and know they WILL work with anything 70.5-87 (wide axle). Can't find anything confirming fitment on narrow axles.

I have an 87 Blazer setup I'd like to install on my 69.

Thanks in advance.
Correct. It will be a bolt-on upgrade for your '69.

ratty69 08-02-2016 10:22 PM
Re: 12 Bolt Drum Brake Upgrade
 
" Correct. It will be a bolt-on upgrade for your '69. "


Sweet. Thanks racecougar!

invicta455 08-04-2016 10:17 AM
Re: 12 Bolt Drum Brake Upgrade
 
Hope to find a set up in the bone yard

SCOTI 11-17-2016 11:47 AM
Re: 12 Bolt Drum Brake Upgrade
 
Quote:
Originally Posted by jjzepplin (Post 7448493)
So I guess the backing plates are offset more to the inside and the shoes are 3/4" wider as well as the drums?
Correct.

Sgtfluffy16 03-15-2018 10:07 PM
Re: 12 Bolt Drum Brake Upgrade
 
I know this is an old thread but i need help I NEED a set of backing plates for my 12 bolt with the 2.75 inch wide shoes. Where can i buy these backing plates. I had a guy send me a set off of these off of this site and i JUST found out they are for the 2 inch wide shoes. nothing will line up. I'm in desperate need of these backing plates. Help me find a set

racecougar 03-15-2018 10:25 PM
Re: 12 Bolt Drum Brake Upgrade
 
AFAIK, the only way to get a set is off a later 12-bolt. I haven't seen them reproduced.

Sgtfluffy16 03-15-2018 10:28 PM
Re: 12 Bolt Drum Brake Upgrade
 
Quote:
Originally Posted by racecougar (Post 8212880)
AFAIK, the only way to get a set is off a later 12-bolt. I haven't seen them reproduced.

so is that going to be a 73-87 chevy k10 pick up? Any thing else i can look for I GOTTA get a set

aggie91 03-16-2018 08:17 AM
Re: 12 Bolt Drum Brake Upgrade
 
Quote:
Originally Posted by Sgtfluffy16 (Post 8212885)
so is that going to be a 73-87 chevy k10 pick up? Any thing else i can look for I GOTTA get a set
Yes, but look at the 1/2 ton vans of the same era, they should have the same rear axle and could possibly have the correct backing plates too.


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