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Author
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Topic: 10 x 2 1/2" Rear Brakes
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ConvertibleKen
Journeyman Posts: 26
From: Riverside California
Registered: OCT 2000
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posted 12-11-2000 08:05 PM
I've read an article by Sam Griffith (Signauenus) regarding upsizing the rear drum brakes to 10 x 2 1/2" for better stopping power. I've located several 1984/85/86 LTD Crown Victoria's at the local self service boneyards. These vehicles come with 8.8 rear ends which use c-clip axle retainers inside the center section instead of retainer plates that mount with the backing plate, like on my 8" stock rear end.
Question is......will these 8.8 backing plates fit on my existing 8" housing flange? And will they fit on a future 9" housing flange? I've been told that the 8" and 9" housing flanges are the same bolt pattern.------------------
70 Mustangs Rule, and Convertibles are the power behind the throne!
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jkilroy
Gearhead Posts: 1811
From: Vicksburg, MS
Registered: DEC 99
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posted 12-11-2000 08:40 PM
What up Ken? Welcome to M&M.8's and 9's have some stuff that will interchange, like axles, but I don't think anything from the 8.8 will swap over. The last time I did a drum brake upgrade was with my old 84 GT. I had swapped a 9" in place of the 7.5 and used backing plates and drums off of a F150. The same parts should bolt up for you also, look for a F150 thats early 80's or before. The big nines are also in Torino's, LTD's all over the place. The F150 drums where at least 10.5 x 2.5. All I know is I had to put in a brake balance valve after I did it cause the back brakes would lock up really easy when they were cold. Like if you could feel the pedal through your shoe they would lock up. Why don't you get a new housing end gasket from the parts store and take it with you to the bone yard. I wouldn't worry about getting the wheel cylinders, buy re-builts for a few bucks each. Also, you *might* need to change your brake lines a little if the rear cylinders have moved much. ------------------
Jay Kilroy
68' Fastback GT 390
"No such thing as a cam thats too big" [This message has been edited by jkilroy (edited 12-11-2000).]
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mellowyellow
Gearhead Posts: 8198
From: So. Fl.
Registered: AUG 2000
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posted 12-11-2000 10:26 PM
Question. What size brakes would be on a 68 Shelby 9" with 3.25 rear. It came out of a GT 350. I now have that rear in my 68 cvt. It has backing plates and that's it. I want to do the same change.
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Moneymaker
Administrator Posts: 29200
From: Lyons, IL, USA
Registered: MAY 99
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posted 12-12-2000 02:12 PM
As long as you have the backing plates Pete, you can put any width shoe that there is a drum available for. Ken, I believe that the backing plates will fit.  Alex------------------
Alex Denysenko Co-Administrator and Moderator
Fleet of FoMoCo's too long to list!
Moneymaker Bio
US Class Nationals link
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mellowyellow
Gearhead Posts: 8198
From: So. Fl.
Registered: AUG 2000
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posted 12-12-2000 02:37 PM
Alex, I believe you but where did all this hoopla start about changing the backing plates??? I wondered about this, too, but figured there was something I didn't know. I plan on buying new drums, hardware, lining and having at it!! Actually, there's a lot I dont't know. LOL!
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CRB
Gearhead Posts: 119
From: Raritan NJ
Registered: JUL 2000
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posted 12-12-2000 03:26 PM
As I understand it the backing plates have a different offset, so you can use the wider drums without changing the width of the rear end.thanks
chip
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Moneymaker
Administrator Posts: 29200
From: Lyons, IL, USA
Registered: MAY 99
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posted 12-12-2000 03:42 PM
I have no idea where all of the "hoopla" started. All I do know is that you can put 1.75, 2.0, or 2.5 linings (brake shoes)on any 10 inch FoMoCo backing plates from the 60's or 70's with the appropriate drums. I have only done it about 1000 times. But, then again, what do I know? Alex------------------
Alex Denysenko Co-Administrator and Moderator
Fleet of FoMoCo's too long to list!
Moneymaker Bio
US Class Nationals link
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Rich Pajzer
Gearhead Posts: 72
From: Newton, New Hampshire Boss 351
Registered: JUN 99
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posted 12-12-2000 05:16 PM
Well, I've only done this once, and no you cant with "any"! Backing plates all have different offsets to position the different width brake shoes in the proper posistion within the drum, and also in order to maintain the proper relationship with the axle flange. The posistion of the axle stud flange doesn't change, so you need a backing plate that offsets inward enough to fit the wider shoes into the drum. You also need backing plates that have the correct bolt spacing and center hole to bolt to the mustangs rear end housing, and also drums with the correct size center hole. 1972 351-429 Ranchero's used 10X 2.5 rear brakes, and is one of the few odd cars where the 72 Ranchero's/Torino's backing plates used the same bolt spacing as the Mustang rear housing. Late 80's Ford Areostar van rear drums, which all had 10x2.5 brakes, will work fine on a 9" rear, and resemble the wide drums used on the Shelby. The ONLY difference is in the casting numbers. (The Ranchero drum is too big externally.)This was all covered in two different Mustang magizines in the early 80's. Did you know that 79 Firebird Trams Am rear discs bolt right onto the mustang housing with a little work. The Pontiac emergency brake even still works. Try to find these parts now though???
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SteveLaRiviere
Administrator Posts: 48752
From: Saco, Maine
Registered: MAY 99
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posted 12-12-2000 05:24 PM
When I swapped my rear drums, {10 x 2.5 from a '70 Torino wagon with 351C/9 inch onto my '72 Mustang with 10 x 1 7/8"} I had to change the backing plates. There was a definite difference in offset. If I recall correctly, I learned that I needed the wagon's backing plates when the drums didn't sit on the axle flanges.------------------
SteveLaRiviere/Webmaster -- MCA # 47773
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sigtauenus
Gearhead Posts: 3969
From: Va Beach
Registered: JUN 2000
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posted 12-12-2000 06:00 PM
Ken, I start with the easy question regarding the interchangability. The Lincoln Town car I took my backing plates off had the c-clip retainers for the axels, but the backing plate still had the same 4 bolt holes for attaching it to the axel, and coincidently its has the same holes to bolt up to your old 8 or 9 inch and fit right.As for the need to use backing plates, I feel uneasy challenging Alex here because he does have more experience than me, but I do believe it is necessary to change the backing plates. If you look at the picture in my tech article, you can see the difference in the sizes of the drums. I think if you originally had 1.75" shoes the corresponding backing plate would not have enough offset to handle the 2.5" drum. You are increasing the width of the drum by 3/4", and there is not that much clearance between the 1.75" drum and backing plate. Thus, when you use the 1.75" backing plate and 2.5" drum, bolt everything together, the drum is going to hit the backing plate before the face of it hits the axel plate that has the lug nuts going through it. As for mellow's question, I think the only 68's that came with 2.5" brakes in the back were 428's.
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brockjoe
Gearhead Posts: 961
From: Sioux City, Iowa
Registered: OCT 99
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posted 12-12-2000 06:32 PM
if you have a 70 torino w/ 10x 2 linings you buy 70 torino 10x 2.5 linings and 70 torino 2.5 drums and it's a bolt up.
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Moneymaker
Administrator Posts: 29200
From: Lyons, IL, USA
Registered: MAY 99
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posted 12-12-2000 06:41 PM
OK, I quit! You guys win. I'm wrong and you're right! End of my participation on the subject. But next time try looking at the damned brake shoes and see how the flanges are centered. I have the FMSI numbers memorized. Alex------------------
Alex Denysenko Co-Administrator and Moderator
Fleet of FoMoCo's too long to list!
Moneymaker Bio
US Class Nationals link
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CRB
Gearhead Posts: 119
From: Raritan NJ
Registered: JUL 2000
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posted 12-13-2000 01:13 PM
First- I am not trying to cause contention, just trying to understand. The size of the standard drums on a 66 are 1.75. There is a small gap (1/4 inch) between the drum and the backing plate. This would indicated the distance from the backing plate to the front of the axle flange (where the drum sits) is about 1.5-1.75 inches. How can a drum that is 2.5 inches sit on the same axle flange and still not hit the backing plate. It seems the drum would extend past the backing plate. If I missed something please explain it. I really am asking this to learn. (Alex your input is also wanted) thanks
chip
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Dave_C
Gearhead Posts: 1123
From: Gadsden, Al
Registered: AUG 99
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posted 12-13-2000 07:16 PM
The drums don't have to hit the backing plates.
I have 11 X 2" drums on the rear of my 69 Fastback drag car. The backing plates were from a 72 Ford truck (came on the rear end that I narrowed). The drums are from a 65 Galaxie. I went with the Galaxie drums due to the bolt pattern for the wheel lugs. 5 on 4.5" vs 5 on 5" for the truck drums.The drums are slightly larger in diameter than the backing plates. The extend to the edge and possibly a hair past the backing plates. Don't see any reason why they couldn't extend past the baking plates as far as needed. Later, David Cole
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ConvertibleKen
Journeyman Posts: 26
From: Riverside California
Registered: OCT 2000
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posted 12-14-2000 02:10 AM
quote:
Originally posted by CRB:
First- I am not trying to cause contention, just trying to understand. The size of the standard drums on a 66 are 1.75. There is a small gap (1/4 inch) between the drum and the backing plate. This would indicated the distance from the backing plate to the front of the axle flange (where the drum sits) is about 1.5-1.75 inches. How can a drum that is 2.5 inches sit on the same axle flange and still not hit the backing plate. It seems the drum would extend past the backing plate. If I missed something please explain it. I really am asking this to learn. (Alex your input is also wanted) thanks
chip
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ConvertibleKen
Journeyman Posts: 26
From: Riverside California
Registered: OCT 2000
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posted 12-14-2000 02:16 AM
The key is in the offset of the backing plate. The 10 x 1.5 backing plate is flat. The 10 x 2.5 backing plate is an inch offset towards the inside. Same axle flange location, but the drums have to be for 2.5 wide shoes to match the plate. Then it all should flow together.------------------
70 Mustangs Rule, and Convertibles are the power behind the throne!
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TomP
Gearhead Posts: 6376
From: Delta BC Canada
Registered: DEC 99
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posted 12-14-2000 04:06 AM
actually not... the drum has more material towards the front side, the 10x 1.75" drums are very domed shaped,the 10 x 2.5" has very squared edges. But there are 2 different offsets on backing plates,the axle bearing to wheel flange dimension can be either 2.25" or 2.5" older ones are the smaller size. You cant just stick Maverick drums on a 57 Ford even if they are both the same lining size. Most other combos will work tho.The Crown Vic backing plates are the same bolt pattern,but what may happen is the rounded lower edge of your axle housing flange may not fit in the recess made for a more rectangular housing end. You can grind the arc-shape flatter (imagine making a "D" into an "[]") I had to do this to use 92 Crown Vic discs on a 9" [This message has been edited by TomP (edited 12-14-2000).]
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CRB
Gearhead Posts: 119
From: Raritan NJ
Registered: JUL 2000
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posted 12-14-2000 09:51 AM
TomP- If I understand you correctly- it is the design (shape) of the drum that is different that makes up for the difference between using 1.75 and 2.5 inch drums? So On my 66 I can use the original backing plate with newer 2.5 inch drums and shoes? The other question is then is all the other hardware the same? thanks
chip
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brockjoe
Gearhead Posts: 961
From: Sioux City, Iowa
Registered: OCT 99
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posted 12-14-2000 11:13 AM
yes the drum has the offset. ALLWAYS replace hardware and software at EVERY brake overhaul.
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Joe
71 Coupe
302 w/2x4
Boycott NASCAR
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steve'66
Gearhead Posts: 9835
From: Sonoma,CA,USA
Registered: MAR 2000
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posted 12-14-2000 11:38 AM
TomP,I'm in the process of changing axles on the '57 9" and the axles from it were 2.25" from bearing to flange. The '66 8" axles are 2.375" from bearing to flange. I had a problem with the drums rubbing the backing plates when using the '57 axles. FWIW I used the '66s backing plates when I did the swap. The new axles will have the '66s dimensions. SteveW
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