#1  
Old 08-07-2019, 07:20 PM
kylek350's Avatar
kylek350 kylek350 is offline
Senior Member
 
Join Date: Aug 2007
Location: Kildeer, IL
Posts: 231
Send a message via AIM to kylek350
Default Same 9.5" Brake Drums for 10 & 12-Bolt Rear Ends?

Are the same 9.5" Drums used on both the 10-bolt and 12-bolt rear ends?

__________________
Kyle Kruszewski
  • 1970 Tempest Post Coupe - Baja Gold, Green interior, 350/TH350 - (1?)32k miles, original condition barring repaint
  • 1970 GTO - Granada Gold, Sandalwood, factory 455/M-21 - Awaiting restoration
  • 1951 Chieftain Deluxe Eight 4-Door Sedan - Saturn Gold, Hydra-Matic - Hibernating since 1969
  #2  
Old 08-08-2019, 09:53 AM
Murf Murf is offline
Ultimate Warrior
 
Join Date: Aug 2000
Location: St. Marys Ks. U.S.A.
Posts: 1,486
Default

I believe they are. When I changed my Firebird from a stock 10 bolt to a 12 bolt, I don’t remember getting different brakes. I ‘m pretty sure I just swapped them over.

It was 20 yrs ago, tho

Murf


Sent from my iPhone using Tapatalk Pro

  #3  
Old 08-08-2019, 10:07 AM
kylek350's Avatar
kylek350 kylek350 is offline
Senior Member
 
Join Date: Aug 2007
Location: Kildeer, IL
Posts: 231
Send a message via AIM to kylek350
Default

Thanks, Murf! I’m pretty sure they’d be the same, but just checking.


Sent from my iPhone using Tapatalk

__________________
Kyle Kruszewski
  • 1970 Tempest Post Coupe - Baja Gold, Green interior, 350/TH350 - (1?)32k miles, original condition barring repaint
  • 1970 GTO - Granada Gold, Sandalwood, factory 455/M-21 - Awaiting restoration
  • 1951 Chieftain Deluxe Eight 4-Door Sedan - Saturn Gold, Hydra-Matic - Hibernating since 1969
  #4  
Old 08-08-2019, 10:36 AM
Murf Murf is offline
Ultimate Warrior
 
Join Date: Aug 2000
Location: St. Marys Ks. U.S.A.
Posts: 1,486
Default

I should add, I swapped backing plates & drums over while changing rear ends.


Sent from my iPhone using Tapatalk Pro

  #5  
Old 08-08-2019, 10:46 AM
Sirrotica's Avatar
Sirrotica Sirrotica is offline
Ultimate Warrior
 
Join Date: Jan 2005
Location: Catawba Ohio
Posts: 7,193
Default

Other than the different divisions used different cooling fin designs, I believe that tons of GM cars used 9.5, 5 X 4.75 bolt circle drums than interchanged. 10 and 12 bolt should make zero difference.

__________________
Brad Yost
1973 T/A (SOLD)
2005 GTO
1984 Grand Prix

100% Pontiacs in my driveway!!! What's in your driveway?

If you don't take some of the RACETRACK home with you, Ya got cheated

  #6  
Old 08-08-2019, 10:56 AM
kylek350's Avatar
kylek350 kylek350 is offline
Senior Member
 
Join Date: Aug 2007
Location: Kildeer, IL
Posts: 231
Send a message via AIM to kylek350
Default

Thanks, Sirrotica!


Sent from my iPhone using Tapatalk

__________________
Kyle Kruszewski
  • 1970 Tempest Post Coupe - Baja Gold, Green interior, 350/TH350 - (1?)32k miles, original condition barring repaint
  • 1970 GTO - Granada Gold, Sandalwood, factory 455/M-21 - Awaiting restoration
  • 1951 Chieftain Deluxe Eight 4-Door Sedan - Saturn Gold, Hydra-Matic - Hibernating since 1969
  #7  
Old 08-09-2019, 07:35 AM
chrisp chrisp is offline
Ultimate Warrior
 
Join Date: Jul 2008
Location: upper dublin Pa.
Posts: 2,937
Default

Quote:
Originally Posted by kylek350 View Post
Are the same 9.5" Drums used on both the 10-bolt and 12-bolt rear ends?
No there is 2 different size register holes.

  #8  
Old 08-09-2019, 10:59 AM
Tom Vaught's Avatar
Tom Vaught Tom Vaught is offline
Boost Engineer
 
Join Date: Dec 2001
Location: The United States of America
Posts: 31,294
Default

Quote:
Originally Posted by chrisp View Post
No there is 2 different size register holes.
I believe that only applies if you are swapping Chevy 12 bolt vs Pontiac 10 bolt.

If you have a 70-72 Pontiac 12 bolt rear axle and swapping 10 bolt for 12 bolt, it should be a exact interchange, IF I remember the one 12 bolt rear I had under by GTO.

Course that was the 12 bolt that blew up like the 10 bolt rears too.

Tom V.

__________________
"Engineers do stuff for reasons" Tom Vaught

Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward.
  #9  
Old 08-09-2019, 11:18 AM
Sirrotica's Avatar
Sirrotica Sirrotica is offline
Ultimate Warrior
 
Join Date: Jan 2005
Location: Catawba Ohio
Posts: 7,193
Default

How is it that the wheels interchange between the two, but brake drums won't ?

Looking at brake drum specs the center hole is within 1/100th of an inch, 2.81 vs 2.82. A rat tail file and 2 minutes will make them the same ID. Rust on an axle flange is many times more than .01 thick, a rat tail file will make short work of that slight interference.

__________________
Brad Yost
1973 T/A (SOLD)
2005 GTO
1984 Grand Prix

100% Pontiacs in my driveway!!! What's in your driveway?

If you don't take some of the RACETRACK home with you, Ya got cheated

  #10  
Old 08-09-2019, 01:29 PM
HWYSTR455's Avatar
HWYSTR455 HWYSTR455 is offline
Ultimate Warrior
 
Join Date: Jan 2005
Location: Manassas, VA
Posts: 14,658
Default

It's the housing tube flange that can be different, due to the tube diameter, which would impact the backing plate fitment. It would look like crap if you tried to wobb it out with a file.

Drums can be slightly different, the depth/axle stand off, but in most cases will 'work'.

EDIT: Have to make sure it's not an 'O' 12 bolt too.

.
Attached Thumbnails
Click image for larger version

Name:	10-12-bolt.jpg
Views:	240
Size:	53.6 KB
ID:	517350   Click image for larger version

Name:	Flanges.jpg
Views:	224
Size:	59.7 KB
ID:	517353  

__________________
.

1970 GTO Judge Tribute Pro-Tour Project 535 IA2
http://forums.maxperformanceinc.com/...d.php?t=760624
1971 Trans Am 463, 315cfm E-head Sniper XFlow EFI, TKO600 extreme, 9", GW suspension, Baer brakes, pro tour car
https://forums.maxperformanceinc.com...ght=procharger
Theme Song: http://www.youtube.com/watch?v=7zKAS...ature=youtu.be

Last edited by HWYSTR455; 08-09-2019 at 01:37 PM.
  #11  
Old 08-09-2019, 02:42 PM
Sirrotica's Avatar
Sirrotica Sirrotica is offline
Ultimate Warrior
 
Join Date: Jan 2005
Location: Catawba Ohio
Posts: 7,193
Default

NO... it's the center hole on the brake drum that is .01 difference.

OPs original question is:

Quote:
Are the same 9.5" Drums used on both the 10-bolt and 12-bolt rear ends?
Not sure how backing plates got into the conversation, or how you turned my statement into opening up the backing plate holes with a file. Pretty sure my statement was the center hole in the brake drum could be opened up .01 if need be.

__________________
Brad Yost
1973 T/A (SOLD)
2005 GTO
1984 Grand Prix

100% Pontiacs in my driveway!!! What's in your driveway?

If you don't take some of the RACETRACK home with you, Ya got cheated

  #12  
Old 08-09-2019, 04:02 PM
HWYSTR455's Avatar
HWYSTR455 HWYSTR455 is offline
Ultimate Warrior
 
Join Date: Jan 2005
Location: Manassas, VA
Posts: 14,658
Default

Guess I didn't read carefully, my bad. I was thinking along the lines of swapping the complete brake setup over from rear to rear, and apologize if it came across as an attack.

.

__________________
.

1970 GTO Judge Tribute Pro-Tour Project 535 IA2
http://forums.maxperformanceinc.com/...d.php?t=760624
1971 Trans Am 463, 315cfm E-head Sniper XFlow EFI, TKO600 extreme, 9", GW suspension, Baer brakes, pro tour car
https://forums.maxperformanceinc.com...ght=procharger
Theme Song: http://www.youtube.com/watch?v=7zKAS...ature=youtu.be
  #13  
Old 08-09-2019, 06:55 PM
Murf Murf is offline
Ultimate Warrior
 
Join Date: Aug 2000
Location: St. Marys Ks. U.S.A.
Posts: 1,486
Default

Quote:
Originally Posted by Sirrotica View Post
NO... it's the center hole on the brake drum that is .01 difference.

OPs original question is:



Not sure how backing plates got into the conversation, or how you turned my statement into opening up the backing plate holes with a file. Pretty sure my statement was the center hole in the brake drum could be opened up .01 if need be.


That’s my fault, guys. I mentioned them in my reply. Sorry if I drove this thread into the ditch!


Sent from my iPhone using Tapatalk Pro

  #14  
Old 11-22-2019, 10:27 PM
Filthy frank Filthy frank is offline
Junior Member
 
Join Date: Nov 2019
Posts: 2
Default Rear axle register

Good question ! Now i have to go measure the register on the 12 bolt axles i made when i owned summers bros and the center of the 11 inch impala rear drum set-up with housing ends i made for a big ford bearing !

  #15  
Old 12-10-2019, 05:04 PM
hobbygto65's Avatar
hobbygto65 hobbygto65 is offline
Ultimate Warrior
 
Join Date: Jan 1970
Location: Brainerd,MN
Posts: 1,767
Default

Just some info, S10 rear brake drums are the same as 8.2. They even have the same part number.

The Following User Says Thank You to hobbygto65 For This Useful Post:
  #16  
Old 12-12-2019, 02:35 PM
jerry455 jerry455 is online now
Senior Chief
 
Join Date: Oct 2007
Location: sterling hts mi
Posts: 296
Default

I upgraded my rear brakes from the 9.5 drum set up to the 11" drums for my 1976 Firebird. I did the 1LE front set up and used the 11" rear drum set up form a 1977 Lemans. Went up an inch in the front and 1.5" in rear. Works great.

  #17  
Old 12-12-2019, 02:49 PM
Filthy frank Filthy frank is offline
Junior Member
 
Join Date: Nov 2019
Posts: 2
Default

Quote:
Originally Posted by jerry455 View Post
I upgraded my rear brakes from the 9.5 drum set up to the 11" drums for my 1976 Firebird. I did the 1LE front set up and used the 11" rear drum set up form a 1977 Lemans. Went up an inch in the front and 1.5" in rear. Works great.
I made impala housing ends to adapt 11 inch drum brakes and big ford bearings and made chevy c clip eliminator axles when i owned summers bros for my 63 nova , but sold the nova and im setting up a chevy rear end for my 63 lamans !

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 06:12 PM.

 

About Us

The PY Online Forums is the largest online gathering of Pontiac enthusiasts anywhere in the world. Founded in 1991, it was also the first online forum for people to gather and talk about their Pontiacs. Since then, it has become the mecca of Pontiac technical data and knowledge that no other place can surpass.

 




Copyright © 2017