rear disc brakes

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Around the middle of September we had a discussion about using 76-78
Cadillac rear disc brakes on the GMC motorhome.

For some reason this discussion abruptly stopped without any conclusions.

Originally Tom Werner wanted to know if anyone had the parts from the 76-78
Cadillac to make the conversion and Patrick Flowers stated he was going to
check his spare rotor and rear drum to see if the front rotor could be used
on the rear hub.

Paul Bartz listed the parts needed to install the Cadillac parts on the GMC.

Since that time I have located the Cadillac parts required and want to know
the following.

1. Tom, are you still interested in developing a lower cost alternative to
the existing suppliers for rear disc brakes and do you still want the
Cadillac parts to evaluate? If you are, I will send you whatever you need as
long as you return them whenever you are through.

2. Patrick, did you ever get a chance to check out the possibility of using
the front rotor ( without modification ) for use on the rear hub?

3. Paul, do you know anyone who has modified the GMC as you described and if
so what are the results?

I hope I am not beating a dead horse by reviving this subject but it appears
that disc brakes have a distinct advantage, especially in mountain driving
and emergency stops as well as being self adjusting, and if many of you are
like me and looking for a low cost alternative to what is presently
available I think we should pursue this until we determine if a low cost
alternative is practical or not.

If anyone wants to refresh their memory on this subject check the posts
around Sept. 14 - 16.

I don't have any answers only questions.

Thanks for any additional information you can provide.

Dick Roberts
Hot and Sunny San Diego
 
Dick I am interested in developing rear disk brakes. AFter the November 2
elections here I will have more time to do it. I am running for Town
Supervisor here.

However I am thinking about starting from scratch and designing the whole
thing using GM off the shelf parts. A dream? Maybe

>Around the middle of September we had a discussion about using 76-78
>Cadillac rear disc brakes on the GMC motorhome.
>
>For some reason this discussion abruptly stopped without any conclusions.
>
>Originally Tom Werner wanted to know if anyone had the parts from the 76-78
>Cadillac to make the conversion and Patrick Flowers stated he was going to
>check his spare rotor and rear drum to see if the front rotor could be used
>on the rear hub.
>
>Paul Bartz listed the parts needed to install the Cadillac parts on the GMC.
>
>Since that time I have located the Cadillac parts required and want to know
>the following.
>
>1. Tom, are you still interested in developing a lower cost alternative to
>the existing suppliers for rear disc brakes and do you still want the
>Cadillac parts to evaluate? If you are, I will send you whatever you need as
>long as you return them whenever you are through.
>
>2. Patrick, did you ever get a chance to check out the possibility of using
>the front rotor ( without modification ) for use on the rear hub?
>
>3. Paul, do you know anyone who has modified the GMC as you described and if
>so what are the results?
>
>I hope I am not beating a dead horse by reviving this subject but it appears
>that disc brakes have a distinct advantage, especially in mountain driving
>and emergency stops as well as being self adjusting, and if many of you are
>like me and looking for a low cost alternative to what is presently
>available I think we should pursue this until we determine if a low cost
>alternative is practical or not.
>
>If anyone wants to refresh their memory on this subject check the posts
>around Sept. 14 - 16.
>
>I don't have any answers only questions.
>
>Thanks for any additional information you can provide.
>
>Dick Roberts
>Hot and Sunny San Diego
>
>
>
>
>
 
Dick:

I know a number of people who have converted to rear wheel disk brakes using
the El Dorado baking plates. I've even driven two of them on the highway.
They equal the braking ability I have with Leigh Harrison's brake system,
since they use a number of the same components.

Paul Bartz

From: warner [mailto:warner]
Sent: Thursday, October 14, 1999 1:59 AM

Dick I am interested in developing rear disk brakes. AFter the November 2
elections here I will have more time to do it. I am running for Town
Supervisor here.

However I am thinking about starting from scratch and designing the whole
thing using GM off the shelf parts. A dream? Maybe

>Around the middle of September we had a discussion about using 76-78
>Cadillac rear disc brakes on the GMC motorhome.
>
>For some reason this discussion abruptly stopped without any conclusions.
>
>Originally Tom Werner wanted to know if anyone had the parts from the 76-78
>Cadillac to make the conversion and Patrick Flowers stated he was going to
>check his spare rotor and rear drum to see if the front rotor could be used
>on the rear hub.
>
>Paul Bartz listed the parts needed to install the Cadillac parts on the
GMC.
>
>Since that time I have located the Cadillac parts required and want to know
>the following.
>
>1. Tom, are you still interested in developing a lower cost alternative to
>the existing suppliers for rear disc brakes and do you still want the
>Cadillac parts to evaluate? If you are, I will send you whatever you need
as
>long as you return them whenever you are through.
>
>2. Patrick, did you ever get a chance to check out the possibility of using
>the front rotor ( without modification ) for use on the rear hub?
>
>3. Paul, do you know anyone who has modified the GMC as you described and
if
>so what are the results?
>
>I hope I am not beating a dead horse by reviving this subject but it
appears
>that disc brakes have a distinct advantage, especially in mountain driving
>and emergency stops as well as being self adjusting, and if many of you are
>like me and looking for a low cost alternative to what is presently
>available I think we should pursue this until we determine if a low cost
>alternative is practical or not.
>
>If anyone wants to refresh their memory on this subject check the posts
>around Sept. 14 - 16.
>
>I don't have any answers only questions.
>
>Thanks for any additional information you can provide.
>
>Dick Roberts
>Hot and Sunny San Diego
>
>
>
>
>
 
Whats wrong for a start of just duplicating the cadillac rear disc brakes
with all of the mods. I can have all of the parts manufactured at a very
reasonable price. Whats anyone else think and how much interest is there?

>Tom, Dick (too bad MY name isn't "Harry") :-))
> I'd love to participate in this project as I have had several
>conversations with the guys at TSM on the topic of moving to 80mm pistons
>for the rears (vs.their current 60 or 65mm units). Had several exchanges
>then this dialog died as well.
>I am DEFINITELY going to slap discs on the back of this sucker (it can't
>come off the blocks until I do) and will spend the grand + to get them from
>TSM or more to get them from the gentleman from Virginia if necessary.
>I've held off on the basis that a little voice in the back of my alleged
>brain keeps screaming that their's a better (and CHEAPER way, which explains
>the voice's Scotch burr).
>If someone wants to spearhead the project, I'd be happy to play a supporting
>role. I've been in the crane, hoist and supporting steel structural design
>business for 30 years and might be able to bring something to the table.
>Given his recent work on the bearing puller, I nominate Town Supervisor
>to-be Tom.
>We may have another GMC guru in the making here.
>Dick 75 PB (in need of bogie brakes) in Atlanta
>
>

>>Dick I am interested in developing rear disk brakes. AFter the November 2
>>elections here I will have more time to do it. I am running for Town
>>Supervisor here.
>>
>>However I am thinking about starting from scratch and designing the whole
>>thing using GM off the shelf parts. A dream? Maybe
>>

>>>Around the middle of September we had a discussion about using 76-78
>>>Cadillac rear disc brakes on the GMC motorhome.
>>>
>>>For some reason this discussion abruptly stopped without any conclusions.
>>>
>>>Originally Tom Werner wanted to know if anyone had the parts from the 76-78
>>>Cadillac to make the conversion and Patrick Flowers stated he was going to
>>>check his spare rotor and rear drum to see if the front rotor could be used
>>>on the rear hub.
>>>
>>>Paul Bartz listed the parts needed to install the Cadillac parts on the GMC.
>>>
>>>Since that time I have located the Cadillac parts required and want to know
>>>the following.
>>>
>>>1. Tom, are you still interested in developing a lower cost alternative to
>>>the existing suppliers for rear disc brakes and do you still want the
>>>Cadillac parts to evaluate? If you are, I will send you whatever you need as
>>>long as you return them whenever you are through.
>>>
>>>2. Patrick, did you ever get a chance to check out the possibility of using
>>>the front rotor ( without modification ) for use on the rear hub?
>>>
>>>3. Paul, do you know anyone who has modified the GMC as you described and if
>>>so what are the results?
>>>
>>>I hope I am not beating a dead horse by reviving this subject but it appears
>>>that disc brakes have a distinct advantage, especially in mountain driving
>>>and emergency stops as well as being self adjusting, and if many of you are
>>>like me and looking for a low cost alternative to what is presently
>>>available I think we should pursue this until we determine if a low cost
>>>alternative is practical or not.
>>>
>>>If anyone wants to refresh their memory on this subject check the posts
>>>around Sept. 14 - 16.
>>>
>>>I don't have any answers only questions.
>>>
>>>Thanks for any additional information you can provide.
>>>
>>>Dick Roberts
>>>Hot and Sunny San Diego
>>>
>>>
>>>
>>>
>>>
>>
>>
>
>
>
 
Hi All

Does anyone have the connections to check out the rear disk brakes used on
the new GMC pickup trucks. If they can be adapted at a reasonable cost they
would have the advantage of being a currently produced, 1999 technology
part. These trucks use 15 or 16" wheels so clearance should not be a
problem. The ABS system is located at the master cylinder so this should
not interfere.

Just a thought. Service on the road would be easier with current parts.

Dave
 
Tom, Dick (too bad MY name isn't "Harry") :-))
I'd love to participate in this project as I have had several
conversations with the guys at TSM on the topic of moving to 80mm pistons
for the rears (vs.their current 60 or 65mm units). Had several exchanges
then this dialog died as well.
I am DEFINITELY going to slap discs on the back of this sucker (it can't
come off the blocks until I do) and will spend the grand + to get them from
TSM or more to get them from the gentleman from Virginia if necessary.
I've held off on the basis that a little voice in the back of my alleged
brain keeps screaming that their's a better (and CHEAPER way, which explains
the voice's Scotch burr).
If someone wants to spearhead the project, I'd be happy to play a supporting
role. I've been in the crane, hoist and supporting steel structural design
business for 30 years and might be able to bring something to the table.
Given his recent work on the bearing puller, I nominate Town Supervisor
to-be Tom.
We may have another GMC guru in the making here.
Dick 75 PB (in need of bogie brakes) in Atlanta


>Dick I am interested in developing rear disk brakes. AFter the November 2
>elections here I will have more time to do it. I am running for Town
>Supervisor here.
>
>However I am thinking about starting from scratch and designing the whole
>thing using GM off the shelf parts. A dream? Maybe
>

>>Around the middle of September we had a discussion about using 76-78
>>Cadillac rear disc brakes on the GMC motorhome.
>>
>>For some reason this discussion abruptly stopped without any conclusions.
>>
>>Originally Tom Werner wanted to know if anyone had the parts from the 76-78
>>Cadillac to make the conversion and Patrick Flowers stated he was going to
>>check his spare rotor and rear drum to see if the front rotor could be used
>>on the rear hub.
>>
>>Paul Bartz listed the parts needed to install the Cadillac parts on the GMC.
>>
>>Since that time I have located the Cadillac parts required and want to know
>>the following.
>>
>>1. Tom, are you still interested in developing a lower cost alternative to
>>the existing suppliers for rear disc brakes and do you still want the
>>Cadillac parts to evaluate? If you are, I will send you whatever you need as
>>long as you return them whenever you are through.
>>
>>2. Patrick, did you ever get a chance to check out the possibility of using
>>the front rotor ( without modification ) for use on the rear hub?
>>
>>3. Paul, do you know anyone who has modified the GMC as you described and if
>>so what are the results?
>>
>>I hope I am not beating a dead horse by reviving this subject but it appears
>>that disc brakes have a distinct advantage, especially in mountain driving
>>and emergency stops as well as being self adjusting, and if many of you are
>>like me and looking for a low cost alternative to what is presently
>>available I think we should pursue this until we determine if a low cost
>>alternative is practical or not.
>>
>>If anyone wants to refresh their memory on this subject check the posts
>>around Sept. 14 - 16.
>>
>>I don't have any answers only questions.
>>
>>Thanks for any additional information you can provide.
>>
>>Dick Roberts
>>Hot and Sunny San Diego
>>
>>
>>
>>
>>
>
>
 
I'm very interested. I conclude that my rear drums have a limited life.
I don't drive in the salt, but they still look bad.
I'd give 'em another 3-4 years tops.
That was the life of other GM drums that looked like these.

Mark

| Subject: Re: GMC: rear disc brakes
|
| Whats wrong for a start of just duplicating the cadillac rear disc brakes
| with all of the mods. I can have all of the parts manufactured at a very
| reasonable price. Whats anyone else think and how much interest is there?
 
Tom:

I believe I could find a number of people who would be interested in
obtaining the requisite backing plates if they knew they were available.
All the other pieces are already available.

If you need it, I have a photo of the backing plate I can scan and e-mail to
you, plus the machining specifications to enlarge the El Dorado plate for it
to fit our axle.

Paul Bartz

From: Mark Grady [mailto:grady]
Sent: Thursday, October 14, 1999 1:17 PM

I'm very interested. I conclude that my rear drums have a limited life.
I don't drive in the salt, but they still look bad.
I'd give 'em another 3-4 years tops.
That was the life of other GM drums that looked like these.

| Subject: Re: GMC: rear disc brakes
|
| Whats wrong for a start of just duplicating the cadillac rear disc brakes
| with all of the mods. I can have all of the parts manufactured at a very
| reasonable price. Whats anyone else think and how much interest is there?
 
Tom, This has 100% of MY attention. If the Caddy parts will fit into the
"envelope" of the 16" diameter wheels, we should go for it. If it weren't
for my CMT (little cousin to MS mainly affecting the lower legs), I'd have
been scrounging the auto junk yards here in Atlanta for the Caddy/Toro parts
necessary. Just can't handle rough terrain as I once did. One more torn up
knee or ankle and my wife has threatened to shoot me! (Didn't mean to wax
apologetic, but as Dirty Harry once remarked "A man's gotta know his
limitations" and this is one of mine. My wife has a long and comprehensive
list of my other limitations.)
Anyway, if we can pull the right stuff together and make it all fit and make
it safe at a reasonable price, I'm on the list for sure.
One of my conversations with TSM was an offer from them to proto an 80mm
piston caliper bracket, they would send it out to me or another cooperating
GMC owner to test fit it under the 16" wheel to check for proper clearance.
The larger caliper pistons offer the potential for making these beasts halt
sooner in those situations where even a few feet make the difference between
"Whew" and "Damn."
Just my nickle's worth.
Dick 75 PB in Atlanta

>Whats wrong for a start of just duplicating the cadillac rear disc brakes
>with all of the mods. I can have all of the parts manufactured at a very
>reasonable price. Whats anyone else think and how much interest is there?
>
>

>>Tom, Dick (too bad MY name isn't "Harry") :-))
>> I'd love to participate in this project as I have had several
>>conversations with the guys at TSM on the topic of moving to 80mm pistons
>>for the rears (vs.their current 60 or 65mm units). Had several exchanges
>>then this dialog died as well.
>>I am DEFINITELY going to slap discs on the back of this sucker (it can't
>>come off the blocks until I do) and will spend the grand + to get them from
>>TSM or more to get them from the gentleman from Virginia if necessary.
>>I've held off on the basis that a little voice in the back of my alleged
>>brain keeps screaming that their's a better (and CHEAPER way, which explains
>>the voice's Scotch burr).
>>If someone wants to spearhead the project, I'd be happy to play a supporting
>>role. I've been in the crane, hoist and supporting steel structural design
>>business for 30 years and might be able to bring something to the table.
>>Given his recent work on the bearing puller, I nominate Town Supervisor
>>to-be Tom.
>>We may have another GMC guru in the making here.
>>Dick 75 PB (in need of bogie brakes) in Atlanta
>>
>>

>>>Dick I am interested in developing rear disk brakes. AFter the November 2
>>>elections here I will have more time to do it. I am running for Town
>>>Supervisor here.
>>>
>>>However I am thinking about starting from scratch and designing the whole
>>>thing using GM off the shelf parts. A dream? Maybe
>>>

>>>>Around the middle of September we had a discussion about using 76-78
>>>>Cadillac rear disc brakes on the GMC motorhome.
>>>>
>>>>For some reason this discussion abruptly stopped without any conclusions.
>>>>
>>>>Originally Tom Werner wanted to know if anyone had the parts from the 76-78
>>>>Cadillac to make the conversion and Patrick Flowers stated he was going to
>>>>check his spare rotor and rear drum to see if the front rotor could be used
>>>>on the rear hub.
>>>>
>>>>Paul Bartz listed the parts needed to install the Cadillac parts on the GMC.
>>>>
>>>>Since that time I have located the Cadillac parts required and want to know
>>>>the following.
>>>>
>>>>1. Tom, are you still interested in developing a lower cost alternative to
>>>>the existing suppliers for rear disc brakes and do you still want the
>>>>Cadillac parts to evaluate? If you are, I will send you whatever you need as
>>>>long as you return them whenever you are through.
>>>>
>>>>2. Patrick, did you ever get a chance to check out the possibility of using
>>>>the front rotor ( without modification ) for use on the rear hub?
>>>>
>>>>3. Paul, do you know anyone who has modified the GMC as you described and if
>>>>so what are the results?
>>>>
>>>>I hope I am not beating a dead horse by reviving this subject but it appears
>>>>that disc brakes have a distinct advantage, especially in mountain driving
>>>>and emergency stops as well as being self adjusting, and if many of you are
>>>>like me and looking for a low cost alternative to what is presently
>>>>available I think we should pursue this until we determine if a low cost
>>>>alternative is practical or not.
>>>>
>>>>If anyone wants to refresh their memory on this subject check the posts
>>>>around Sept. 14 - 16.
>>>>
>>>>I don't have any answers only questions.
>>>>
>>>>Thanks for any additional information you can provide.
>>>>
>>>>Dick Roberts
>>>>Hot and Sunny San Diego
>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>
>>
>>
>
>
 
would love to see it paul. Please send it.

>Tom:
>
>I believe I could find a number of people who would be interested in
>obtaining the requisite backing plates if they knew they were available.
>All the other pieces are already available.
>
>If you need it, I have a photo of the backing plate I can scan and e-mail to
>you, plus the machining specifications to enlarge the El Dorado plate for it
>to fit our axle.
>
> Paul Bartz
>
>From: Mark Grady [mailto:grady]
>Sent: Thursday, October 14, 1999 1:17 PM
>
>I'm very interested. I conclude that my rear drums have a limited life.
>I don't drive in the salt, but they still look bad.
>I'd give 'em another 3-4 years tops.
>That was the life of other GM drums that looked like these.
>

>| Subject: Re: GMC: rear disc brakes
>|
>| Whats wrong for a start of just duplicating the cadillac rear disc brakes
>| with all of the mods. I can have all of the parts manufactured at a very
>| reasonable price. Whats anyone else think and how much interest is there?
>
>
 
Thanks Tom,Paul and everyone who has responded to the rear disc brake
discussion.(Still waiting to hear from Patrick about the use of front rotors
on the rear.) (G)

Paul published a list of parts required to convert to rear disc brakes using
Cadillac parts. (Dated 9/15/99) I am assuming that the installation used the
following parts.

1. 1976-78 Cadillac rear disc brake backing plates with center hole machined
to 2.250"and chamfer on rear of hole, no other modifications needed.
Requires a total of 4 backing plates.

2. 1976-78 Cadillac rear disc brake rotors. Total of 4 rotors.These are 5
hole rotors that need to have 3 additional holes drilled using the same size
holes and bolt circle. Of these 8 holes only 4 are used to attach the rotor
to the original GMC rear hubs. (Three of the original holes will not be used
since they will not match the bolt pattern of the hub. This would leave 4 of
the holes in the hub unused. Center hole of rotor needs to be machined to
the OD of the hub. (I don't know this dimension but assume it is around 4".

3. 1976-78 Cadillac rear calipers. A total of two to be used on the
rear-rear axles. This allows the emergency brake to be utilized on the
rear-rear axle.

4. Two 80 mm calipers to be used on the front-rear axle to provide
additional braking power. No emergency brake is possible with these
calipers.

5. Due to weight transfer during braking, the front-rear needs the larger
calipers and better pads. If these were also installed on the rear-rear axle
the rear-rear wheels would probably lock up under heavy braking.

6. Because of the larger front-rear calipers (80mm) it is necessary to use a
larger master cylinder.

7. There are no other major modification required to change from drum to
disc brakes, (No spacers required, no clearance problems,etc.)

Paul or anyone else knowledgeable please confirm or correct the above
assumptions.

I have a couple of other questions and comments.

1.Since the cost of rebuilt Cadillac rear calipers is so high ($70 - $100) I
am thinking of buying a rebuild kit ($15-$20) and doing the rebuild myself.
Any suggestions or advise?

2. I do not want to use a larger master cylinder at this time and would like
to have emergency brakes on all four rear wheels, so I am thinking about
using the Cadillac rear calipers on all four rear wheels. (I already have
the parts out of a junkyard) Is there any other downside other than the
braking is somewhat better with 80mm? (Still much better than original)

3. When installing the rear disc brakes are the calipers oriented in the
same position as on the Cadillac or do they have to be rotated to accomodate
the emergency brake,etc?

I appreciate any and all comments / information.

Dick Roberts
 
Do you have the part # for the master cylinder or know the aplication or
just cylinder bore?
Thanks
R/A
Bandon Or
- -----Original Message-----
From: rtroberts
To: gmcmotorhome
Date: Thursday, October 14, 1999 9:33 PM
Subject: Re: GMC: Rear disc brakes

>
>Thanks Tom,Paul and everyone who has responded to the rear disc brake
>discussion.(Still waiting to hear from Patrick about the use of front
rotors
>on the rear.) (G)
>
>Paul published a list of parts required to convert to rear disc brakes
using
>Cadillac parts. (Dated 9/15/99) I am assuming that the installation used
the
>following parts.
>
>1. 1976-78 Cadillac rear disc brake backing plates with center hole
machined
>to 2.250"and chamfer on rear of hole, no other modifications needed.
>Requires a total of 4 backing plates.
>
>2. 1976-78 Cadillac rear disc brake rotors. Total of 4 rotors.These are 5
>hole rotors that need to have 3 additional holes drilled using the same
size
>holes and bolt circle. Of these 8 holes only 4 are used to attach the rotor
>to the original GMC rear hubs. (Three of the original holes will not be
used
>since they will not match the bolt pattern of the hub. This would leave 4
of
>the holes in the hub unused. Center hole of rotor needs to be machined to
>the OD of the hub. (I don't know this dimension but assume it is around 4".
>
>3. 1976-78 Cadillac rear calipers. A total of two to be used on the
>rear-rear axles. This allows the emergency brake to be utilized on the
>rear-rear axle.
>
>4. Two 80 mm calipers to be used on the front-rear axle to provide
>additional braking power. No emergency brake is possible with these
>calipers.
>
>5. Due to weight transfer during braking, the front-rear needs the larger
>calipers and better pads. If these were also installed on the rear-rear
axle
>the rear-rear wheels would probably lock up under heavy braking.
>
>6. Because of the larger front-rear calipers (80mm) it is necessary to use
a
>larger master cylinder.
>
>7. There are no other major modification required to change from drum to
>disc brakes, (No spacers required, no clearance problems,etc.)
>
>Paul or anyone else knowledgeable please confirm or correct the above
>assumptions.
>
>I have a couple of other questions and comments.
>
>1.Since the cost of rebuilt Cadillac rear calipers is so high ($70 - $100)
I
>am thinking of buying a rebuild kit ($15-$20) and doing the rebuild myself.
>Any suggestions or advise?
>
>2. I do not want to use a larger master cylinder at this time and would
like
>to have emergency brakes on all four rear wheels, so I am thinking about
>using the Cadillac rear calipers on all four rear wheels. (I already have
>the parts out of a junkyard) Is there any other downside other than the
>braking is somewhat better with 80mm? (Still much better than original)
>
>3. When installing the rear disc brakes are the calipers oriented in the
>same position as on the Cadillac or do they have to be rotated to
accomodate
>the emergency brake,etc?
>
>I appreciate any and all comments / information.
>
>Dick Roberts
>
>
>
>
 
>
> Thanks Tom,Paul and everyone who has responded to the rear disc brake
> discussion.(Still waiting to hear from Patrick about the use of front rotors
> on the rear.) (G)

Dick, I'm away from home until Sunday. I'll try to have a look at the
rotor and drum Sunday or Monday evening.

Patrick
- --
Patrick Flowers
Mailto:patrick

The GMC Motorhome Page
http://www.gmcmotorhome.com
 
From: "R Anderson"
Subject: Re: GMC: Rear disc brakes

Do you have the part # for the master cylinder or know the aplication or
just cylinder bore?
Thanks
R/A
Bandon Or

R Anderson,

Is this the information you are looking for?

Dick Roberts
>
>Although there was some degree of controversy on this subject a number
>of
>months back, you may want to consider going to a larger master cylinder
>if
>making the switch to larger the calipers. If so, it's available from
>Autozone, p/n 10166, $53.43, and does require an ~ 0.010" longer brake
>rod
>(p/n GM 5469384)(between master cylinder and brake booster) as well as a
>
>modified mounting bracket. If you need further details on this
>modification, let me know.
>
> Paul Bartz
>
 
Thanks Dick
Yess that was what i was looking for.
R/A
- -----Original Message-----
From: rtroberts
To: gmcmotorhome
Date: Friday, October 15, 1999 9:00 AM
Subject: Re: GMC: Rear Disc Brakes

> From: "R Anderson"
>Subject: Re: GMC: Rear disc brakes
>
>Do you have the part # for the master cylinder or know the aplication or
>just cylinder bore?
>Thanks
>R/A
>Bandon Or
>
>R Anderson,
>
>Is this the information you are looking for?
>
>Dick Roberts
>>
>>Although there was some degree of controversy on this subject a number
>>of
>>months back, you may want to consider going to a larger master cylinder
>>if
>>making the switch to larger the calipers. If so, it's available from
>>Autozone, p/n 10166, $53.43, and does require an ~ 0.010" longer brake
>>rod
>>(p/n GM 5469384)(between master cylinder and brake booster) as well as a
>>
>>modified mounting bracket. If you need further details on this
>>modification, let me know.
>>
>> Paul Bartz
>>
>
>
>
>
>
>
 
Put me down as interested. I'd love to have 6 wheel disks but don't want
to spend thousands of dollars on it.

bdub

>Whats wrong for a start of just duplicating the cadillac rear disc brakes
>with all of the mods. I can have all of the parts manufactured at a very
>reasonable price. Whats anyone else think and how much interest is there?
 
I'm interested keep me posted.

> Whats wrong for a start of just duplicating the cadillac rear disc brakes
> with all of the mods. I can have all of the parts manufactured at a very
> reasonable price. Whats anyone else think and how much interest is there?
>
 
From: rtroberts [mailto:rtroberts]
Sent: Friday, October 15, 1999 12:31 AM

Thanks Tom, Paul and everyone who has responded to the rear disc brake
discussion.(Still waiting to hear from Patrick about the use of front rotors
on the rear.) (G)
Paul published a list of parts required to convert to rear disc brakes using
Cadillac parts. (Dated 9/15/99) I am assuming that the installation used the
following parts.
1. 1976-78 Cadillac rear disc brake backing plates with center hole machined
to 2.250" and chamfer on rear of hole, no other modifications needed.
Requires a total of 4 backing plates.
2. 1976-78 Cadillac rear disc brake rotors. Total of 4 rotors.These are 5
hole rotors that need to have 3 additional holes drilled using the same size
holes and bolt circle. Of these 8 holes only 4 are used to attach the rotor
to the original GMC rear hubs. (Three of the original holes will not be used
since they will not match the bolt pattern of the hub. This would leave 4 of
the holes in the hub unused. Center hole of rotor needs to be machined to
the OD of the hub. (I don't know this dimension but assume it is around 4".
Dimension is 3.875" with 45 degree x 1/16" chamfer on the front side.
3. 1976-78 Cadillac rear calipers. A total of two to be used on the
rear-rear axles. This allows the emergency brake to be utilized on the
rear-rear axle.
4. Two 80 mm calipers to be used on the front-rear axle to provide
additional braking power. No emergency brake is possible with these
calipers.
5. Due to weight transfer during braking, the front-rear needs the larger
calipers and better pads. If these were also installed on the rear-rear axle
the rear-rear wheels would probably lock up under heavy braking.
6. Because of the larger front-rear calipers (80mm) it is necessary to use a
larger master cylinder.
7. There are no other major modification required to change from drum to
disc brakes, (No spacers required, no clearance problems,etc.)
Paul or anyone else knowledgeable please confirm or correct the above
assumptions.
I have a couple of other questions and comments.
1.Since the cost of rebuilt Cadillac rear calipers is so high ($70 - $100) I
am thinking of buying a rebuild kit ($15-$20) and doing the rebuild myself.
Any suggestions or advise?
2. I do not want to use a larger master cylinder at this time and would like
to have emergency brakes on all four rear wheels, so I am thinking about
using the Cadillac rear calipers on all four rear wheels. (I already have
the parts out of a junkyard) Is there any other downside other than the
braking is somewhat better with 80mm? (Still much better than original)
3. When installing the rear disc brakes are the calipers oriented in the
same position as on the Cadillac or do they have to be rotated to accomodate
the emergency brake, etc?
Backing plate on the leading wheel is oriented so that the caliper faces the
front of the coach. Opposite for the trailing wheel.
 
Paul and Patrick.

Thanks for your responses regarding rear disc brakes.

Dick Roberts
>radius than the drum bolt circle. Also, the inner radius of the
>rotor(where the hub passes through) is approximately 1/4 inch smaller
>than that of the brake drum.
>
>Patrick
>- --
 
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