Backing Plates?

Backing Plates?

Postby Astro Pop [OP] » April 19th 2017, 5:19am

Has anyone found a source for the drum brake backing plates? Been looking for a month. Mine are so grooved from the shoes riding on them that they now hang up in the grooves.
Anyone....anyone?
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Re: Backing Plates?

Postby MI_Ghost » April 19th 2017, 9:18am

As you will have to pull the axle shafts to remove the backing plates. Why not just upgrade to the proven 11" drum brake upgrade. Either way you are looking at sourcing used backing plates.

It would be necessary to find out what the change was on the 98-02 axle to determine if those backing plates will interchange. The only thing I can come up with is a change from a self tapping screw to an M6 bolt. Maybe for the wheel cylinder??

CargoCrawler has done the 11" brake on a 98 and markmitch has done it on a 89. I see no reason why the later backing plates will not work on the earlier axle. But your still looking for a used Left side.

85-97
PLATE. Brake Flange/Backing R (Discontinued)
Part Number: 18012022 ; 18012153

PLATE. Brake Flange/Backing L (Discontinued)
Part Number: 18012021 ; 18012152;

Which interchange with 92-97 S-10/Blazer, 94-96 Caprice/Impala, 93-97 Camaro/Firebird

98-02
PLATE. Brake Flange/Backing R
Part Number: 18046187 ; 18046191
98-02 Astro/Safari

PLATE. Brake Flange/Backing L (Discontinued)
Part Number: 18046186 ; 18046190
98-02 Astro/Safari

Which curiously enough interchange with the 98-03 S-10/Blazer that also came equipped with rear disc brakes.
If the rear disc conversion might tickle your fancy. You van find a great write up on it over on NastyZ28.
http://nastyz28.com/threads/s10-blazer- ... on.109454/
~Ghost
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Re: Backing Plates?

Postby Astro Pop [OP] » April 19th 2017, 5:14pm

Thanks Ghost. I was thinking of that anyway, just at some later date. So I'll do it now. My only question is that he mentions 2 LH Calipers for the changing the Camaro. Do you think that is true for the Astro conversion too?
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Re: Backing Plates?

Postby MI_Ghost » April 19th 2017, 11:08pm

Astro Pop wrote:Thanks Ghost. I was thinking of that anyway, just at some later date. So I'll do it now. My only question is that he mentions 2 LH Calipers for the changing the Camaro. Do you think that is true for the Astro conversion too?


The shock placement on the Camaro is the reason for the 2 left calipers. On the Camaro and S-10 the shocks are mounted out at the springs. This makes the staggered front/rear caliper mounting necessary on the Camaro to avoid conflict with the shocks. In this case the calipers are the same part.

The Astro has the shocks mounted a few inches inward from the springs so this issue with the shocks is not present. You can do either the front mount calipers or the staggered front/rear mount calipers on the Astro. Only the staggered mount will require the 2 left calipers.

You need to note also that it is a combination of 2WD and 4WD parts used. The S-10/Blazer fill the junk yards right now so if you have problems finding the backing/mounting plates new. They will be easy to find at a U-pull. If you go the U-pull route get the mounting plates and calipers from the same axle. Use the calipers for the core charge on new ones.

Here are the part #'s for all the possible backing/mount plates for the S-10/Blazer
Parking Brake/ Caliper Mount Plate S10/Blazer
s10 2wd
GM 18046187 L 98-03
GM 18046186 R 98-03
GM 18043288 L&R 00-02

Blazer 2wd Staggered Shock
GM Part 12376603 L 98-00
GM Part 12376604 R 98-00
GM Part 88935975 L 01-05
GM Part 88935976 R 01-05

Blazer/S10 4wd
GM Part 88935985 L 98-05
GM Part 88935986 R 98-05

This is not a confirmed bolt on.
As this has not been done specifically on an Astro axle yet. There are unanswered questions that I still have.

Brake Rotors:
Which rotors? 94-96 Impala?
The 94-96 Impala was the go to conversion for rear disc brakes but part shortage has made this extremely difficult to put together the needed parts. The 94-96 impala disc brakes have been done on the Astro and is a confirmed bolt on. I have not found a good reference to compare the Impala and S-10 brakes as yet.
The difference in wheel bolt circle eliminates the S-10/Blazer rotors. Redrilled rotors possible??
There is a 0.53" difference in rotor height. Impala: Height - 2.34", S-10: Height - 2.87". This is a factor for the spacer used to mount the plate to the axle. Might need a 0.75"-0.78" thick spacer instead of 0.25" thick spacer in the write up.

Edit:
Another possible option is the caliper mounting brackets. I have not looked into this to see if the Impala brackets will bolt to the S-10 backing plates.


Which parking brake cables?
I have not done much research on this. I still have questions about length, routing, and connections.

The S-10 rear disc conversion has always been dismissed on the bases of the difference in the bolt circles but that only affects the rotor. The actual working parts (Mounting plate, Calipers) of the system will mount up to the Astro axle. Redrilled rotors or thicker spacer could make this possible.
~Ghost
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Re: Backing Plates?

Postby MI_Ghost » April 20th 2017, 8:40am

Here is the other post that was done on it.
http://nastyz28.com/threads/blazer-s10-rear-disc.94303/

Did some looking in to this again. The Kits which include backing plate, dust shield, hardware, and parking brake lining are still showing available. Not badly priced either.

BRAKE. Parking Brake Apply
Part Number: 15064303 ; 15047016
BRAKE,PARK(INCLS BRAKE KIT, LINING KIT, PLATE & SHIELD) - RH
97-05 S-10/Blazer

BRAKE. Parking Brake Apply
Part Number: 15064302 ; 15047015
BRAKE,PARK(INCLS BRAKE KIT, LINING KIT, PLATE & SHIELD) - LH.
97-05 S-10/Blazer

I do not know if these are staggered or front mount.
Calipers and rotors are commonly available.

One other note on the rotors.
If you go the route of redrilling the S-10 rotors to fit the 5x5 bolt circle. You will also need to open up the center hole to fit the axle hub. Astro/Impala: 3.07", S-10: 2.79"

Did some looking in to the parking brake cables also.
The great news is that the connector for the front and rear cables is the same for all 85-02, and the front cable for the 03-05 is the same as for all 96-05. That means the 03-05 parking brake cables are a possible option. There is different hardware to connect to the front cable which is still available but the cable has the eyelet end need for the parking brake application. The only concern would be if the eyelet is the correct size, This will be easy to check.

I definitely think this is possible. The rotor/caliper spacing is about the only issue and you deal with that on any rear disc conversion.

I will put together a parts list and get it posted.
Thanks for the push to finally finish my research on this.
~Ghost
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Re: Backing Plates?

Postby MI_Ghost » April 21st 2017, 9:19am

This is the post that I take as confirmation that the S-10/Blazer rear disc will work.
http://nastyz28.com/threads/s10-blazer- ... st-2300604
I used the rear from a 94 Caprice 9C1, a 10-bolt with larger 30-spline axles and used the S10 backing plates but two passenger side 9C1 calipers with matching caliper brackets. Not sure if there's a performance advantage but when looking at the S10 vs 9C1 caliper, the 9C1 seemed better. Since the Caprice is 5x5, I used Caprice rotors, but the backing plates required a 1/2" spacer at the axle housing to get everything to line up properly. An Impala SS donated its front spindles to the cause and finished the 5x5 conversion.


As noted in bold above. The use of the Caprice/Impala Rotors will need a 0.50" spacer between the axle housing and backing plate to center the caliper on the rotor. These will be the only special made parts needed (QTY:2).

With the 94-96 Caprice/Impala rear disc being a confirmed fit.
This makes the parts for the conversion as follows.

98-05 S-10/Blazer 4WD backing plates. (Front Mount Calipers)
GM Part 88935985 L 98-05 Front Mount, 88935987 (Left Dust Shield)
https://www.amazon.com/ACDelco-88935985 ... B004JBG276
GM Part 88935986 R 98-05 Front Mount, 88935988 (Right Dust Shield)
https://www.amazon.com/ACDelco-88935986 ... B004JBC784

94-96 Caprice/Impala Calipers
94-96 Caprice/Impala Rotors
94-96 Caprice/Impala Flex Hoses (May need adapter to Astro hard line)

03-05 Astro Parking brake cables (Still need confirmation)
Left: ACDELCO 18P2786
Right: ACDELCO 18P97205

Parking brake shoe & hardware
94-96 Caprice/Impala and 98-05 S-10/Blazer use the same parking brake shoe

94-96 Caprice/Impala
Parking Brake Kit ACDelco GM Original Equipment 179-2115 (Kit includes both sides)

98-05 S-10/Blazer
BRAKE KIT. Parking Brake Shoe
Part Number: 12376596
BRAKE KIT,RR PARK(INCLS LEVER, ROD, PAWLS, LINING & SPRINGS)(ACDelco #179-2047)
NOTE:(This can easily wipe out any savings of buying separate parts)

The backing plate kits noted earlier are the front mount plates but price shopping shows it to be much cheaper to buy the separate parts if you can get the break lining kit at a good price.

BRAKE. Parking Brake Apply
Part Number: 15064303 ; 15047016
BRAKE,PARK(INCLS BRAKE KIT, LINING KIT, PLATE & SHIELD) - RH
97-05 S-10/Blazer

BRAKE. Parking Brake Apply
Part Number: 15064302 ; 15047015
BRAKE,PARK(INCLS BRAKE KIT, LINING KIT, PLATE & SHIELD) - LH.
97-05 S-10/Blazer
~Ghost
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User avatar
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