Drum Brakes

[john phillips]

If I replace the drums and shoes on my 26 foot Avion how long should I expect the shoes to last and how many sets of shoes should I expect the drums
to last if I do not let the shoes get down the rivets or metal? What about adding Applied Control Arms to the drum brake repair?

How does that compare to replacing with a disc system such as Manny's Brakes?

--
Johnd01
John Phillips
Avion A2600 TZE064V101164
Rancho Cordova, CA (Sacramento)

 

[jim kanomata1]

I might be partial , but we test our units instead of just manufacturing
them.
I'm on the tied till Wednesday , but we can discuss how each work and maybe
you might decide you might need not spend on other non stock unit
800-752-7502

On Sat, Apr 14, 2018 at 8:12 PM John Phillips
wrote:

> If I replace the drums and shoes on my 26 foot Avion how long should I
> expect the shoes to last and how many sets of shoes should I expect the
> drums
> to last if I do not let the shoes get down the rivets or metal? What about
> adding Applied Control Arms to the drum brake repair?
>
> How does that compare to replacing with a disc system such as Manny's
> Brakes?
>
> --
> Johnd01
> John Phillips
> Avion A2600 TZE064V101164
> Rancho Cordova, CA (Sacramento)
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.appliedgmc.com
1-800-752-7502

 

[john r. lebetski]

Rear linings can last 500 miles or 50,000 miles all depending on driver habits. If you don't overheat and warp the drums then hardly any material
needs to be removed to resurface them and they will be within safe thickness spec. Probably for our lifetime.
--
John Lebetski
Woodstock, IL
77 Eleganza II

 

[Matt Colie]

John,

Before you go an mess with the brakes, find out all about what can be done. There are some issues with everything people do.

To answer your question as well as I can in the dark (we are at home, but on our own power and batteries), my coach still has the original drums at
170k. I did a very complete brake job about 3 years back (coach at 150K, but I can't get at that book right now because the power is out and my barn
is dangerous in the dark. The three remaining brake drums were all the original that were replace with a recall in about 1975 and I do not know the
miles on them exactly. When I did that rear brake job, the shoes that had to have at least 70K on then (how long we have has Chaumière) still had
room over the rivets.

Why three brake drums is a three beer story and I do not have the battery for it right now.

One thing I will tell (as will anybody else that has done the mod) the "Reaction Arms" on drum rear are a really good investment.

Mine is a lighter coach than most, but our stopping capability is very car like and without drama. I can and have locked the intermediate rears.
Actually, I can do a controlled lock of all four rears.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit

 

[Ken B]

On a 4 wheel vehicle weighing 1/2 that of a GMC we usually say 65 to 70% of the braking is done on the front wheels. On a GMC we have he same front
calipers and pads as cars and PU trucks of that era with double the weight. We also have 4 rear braking wheels instead of 2. So I assume that front
to rear ratio has changed some but probably not more than 50/50 front to rear.

Some people have tried improving the rear wheel braking only to have their rear wheels lock up on moderate braking. A lot of playing around with
both the front and rear braking has been done on the GMC and some improvements have been accomplished.

I have never needed to replace the rear shoes while I have replaced the front pads twice. So I still think that the rears have very little braking
effect on a stock GMC and that braking is spread over 4 rear wheels not the customary 2. So there is minimal rear shoe wear.

I do not have rear automatic adjusters. Some PO removed them years ago. I manually adjust the rears every year or 2 and it does not take more than
a few clicks. So I have very little rear shoe wear on my stock GMC brakes.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

 

[john phillips]

Thanks for the information. I need to replace the shoes on the center axle.
The Wheel cylinders on that axle are leaking but the shoes are worn out as
well. The back axle looks good with no leaks. My drums have been turned a
few times. They are close to maximum. Not sure if there is enough metal
left to turn them again. I wish the odometer had 1 or maybe 2 more digits.
Looking at the drums I am thinking this coach probably has more than 200k
miles. Looking at replacing all 4 drums and thinking rather than buying
more drums I should put some shoes in what I have and take it to someone
who would do a disk conversion.

It is also about time to do something with the front wheel bearings.
Last summer I talked to Manny about doing both but he told me to only do
one at a time.
I would not mind staying with drums. Do disks dissipate heat significantly
faster than drums?
Uniformity and control are the keys to good stopping all the tires should
lockup at the same time and there should be enough control the not quite
lock them up.

John Phillips
75 Avion vin A26000
Rancho Cordova ca.

> On a 4 wheel vehicle weighing 1/2 that of a GMC we usually say 65 to 70%
> of the braking is done on the front wheels. On a GMC we have he same front
> calipers and pads as cars and PU trucks of that era with double the
> weight. We also have 4 rear braking wheels instead of 2. So I assume that
> front
> to rear ratio has changed some but probably not more than 50/50 front to
> rear.
>
> Some people have tried improving the rear wheel braking only to have their
> rear wheels lock up on moderate braking. A lot of playing around with
> both the front and rear braking has been done on the GMC and some
> improvements have been accomplished.
>
> I have never needed to replace the rear shoes while I have replaced the
> front pads twice. So I still think that the rears have very little braking
> effect on a stock GMC and that braking is spread over 4 rear wheels not
> the customary 2. So there is minimal rear shoe wear.
>
> I do not have rear automatic adjusters. Some PO removed them years ago.
> I manually adjust the rears every year or 2 and it does not take more than
> a few clicks. So I have very little rear shoe wear on my stock GMC
> brakes.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--

*John Phillips*

 

[Ken B]

John,

I am not the one to advise on the merits or cost of going to rear disks. I have never done it. There are many here who have. So I'll defer comment
to them. I will say that there are many cars and trucks that still use drum rear brakes. My two Blazers have rear disks while my newer Colorado and
Heather's 2016 Honda has rear drums.

On the drums. The existing drums do not necessarily need to be turned. Some drum grooving with the installation of new shoes is allowable. So maybe
new drums or turned drums are not be necessary. If the rivets or shoe metal frames have not worn off enough braking material hit the drums, it
probably would be OK to use the drums as is and just install new shoes. I would have to see them in person to make that determination. On the
replacement of wheel cylinders. I suggest that you go to 1-1/16 cylinder for the mid axle and OEM 15/16" on for the rear axle if they need to be
replaced. Both sizes are cheap (less than $10.00 each). I do not have the part numbers in front of me but I'm sure the GMCMI or bdub parts look up
on line will have them. I did mine over 10 years ago and did not keep any records at the time. They were in stock at AutoZone and cheap.

Here I stole this from GMCMI on line. Do not tell anyone.

Wheel Cylinder, Oversize 1 1/16″
All Pro Rockhill (See #55, Page 3)WC13709
Bendix (See #55, Page 3)33709
Carlson (See #18, Pg 2, #36, Pg 3 & #55, P345024
EIS (See #55, Page 3)EW79767
NAPA United (UP)37290
Wagner (See #55-3, #18-2, #36-3)F7976

Wheel Cylinder, Standard 15/16″
GMC 78Z Parts Book-Superseded 5469302
All Pro Rockhill WC13469
Bendix-(Lines will need to be bent) 33469
Car Quest EW51081
Carlson 45003
Delco 172-1219 EIS51081 GMC18004890
NAPA United (UP)37048
Pontiac Bonneville (65-70)Reference
Raybestos 37048
Wagner 51081

One thing I should mention. People have been installing a rear reaction arm system with both drum and disk brakes. They seem to be very happy with
it. Again. I have never done it but you might want to look into that also.

Jim K. at Applied GMC sells the reaction arm and just about everything else GMC. I know Matt has installed it with drums and probably Colonel Ken has
done it with disks. I know that there are also many others. Matt Colie and Colonel Ken Henderson are good resources that will not steer you wrong.


You have lots of decisions to make. Good luck
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

 

[john phillips]

Thank you Ken

> John,
>
> I am not the one to advise on the merits or cost of going to rear disks.
> I have never done it. There are many here who have. So I'll defer comment
> to them. I will say that there are many cars and trucks that still use
> drum rear brakes. My two Blazers have rear disks while my newer Colorado
> and
> Heather's 2016 Honda has rear drums.
>
> On the drums. The existing drums do not necessarily need to be turned.
> Some drum grooving with the installation of new shoes is allowable. So
> maybe
> new drums or turned drums are not be necessary. If the rivets or shoe
> metal frames have not worn off enough braking material hit the drums, it
> probably would be OK to use the drums as is and just install new shoes. I
> would have to see them in person to make that determination. On the
> replacement of wheel cylinders. I suggest that you go to 1-1/16 cylinder
> for the mid axle and OEM 15/16" on for the rear axle if they need to be
> replaced. Both sizes are cheap (less than $10.00 each). I do not have
> the part numbers in front of me but I'm sure the GMCMI or bdub parts look up
> on line will have them. I did mine over 10 years ago and did not keep any
> records at the time. They were in stock at AutoZone and cheap.
>
> Here I stole this from GMCMI on line. Do not tell anyone.
>
> Wheel Cylinder, Oversize 1 1/16″
> All Pro Rockhill (See #55, Page 3)WC13709
> Bendix (See #55, Page 3)33709
> Carlson (See #18, Pg 2, #36, Pg 3 & #55, P345024
> EIS (See #55, Page 3)EW79767
> NAPA United (UP)37290
> Wagner (See #55-3, #18-2, #36-3)F7976
>
> Wheel Cylinder, Standard 15/16″
> GMC 78Z Parts Book-Superseded 5469302
> All Pro Rockhill WC13469
> Bendix-(Lines will need to be bent) 33469
> Car Quest EW51081
> Carlson 45003
> Delco 172-1219 EIS51081 GMC18004890
> NAPA United (UP)37048
> Pontiac Bonneville (65-70)Reference
> Raybestos 37048
> Wagner 51081
>
> One thing I should mention. People have been installing a rear reaction
> arm system with both drum and disk brakes. They seem to be very happy with
> it. Again. I have never done it but you might want to look into that
> also.
>
> Jim K. at Applied GMC sells the reaction arm and just about everything
> else GMC. I know Matt has installed it with drums and probably Colonel Ken
> has
> done it with disks. I know that there are also many others. Matt Colie
> and Colonel Ken Henderson are good resources that will not steer you
> wrong.
>
>
> You have lots of decisions to make. Good luck
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--

*John Phillips*

 

[dave stragand1]

Ken,

Will installing the larger rear wheel cylinders have any effect on the braking when braking boost is lost? Does is help or hurt in that situation.

Thanks,

-Dave
Near Pittsburgh
1978 Transmode

 

[Matt Colie]

> Ken,
>
> Will installing the larger rear wheel cylinders have any effect on the braking when braking boost is lost? Does is help or hurt in that
> situation.
>
> Thanks,
>
> -Dave
> Near Pittsburgh
> 1978 Transmode

Dave,

This is one of those times when geography matters. I will get back to that.

Something for you to try is:
Find a big open area.
Get the coach rolling, and shut the engine down.
Put one short jab on the brake pedal to blow the vacuum in the booster.
Now - see if you can stop the coach before Thursday.......

With no or little assist from the booster (you get only one try and not the two you have been told), it is very difficult to stop a 12K# coach. For
this reason, the first thing you should consider adding is some back-up vacuum system. Be it electric or just a HUGE reservoir, where you live I
would consider this essential to survival.

I can't tell you if there is any modification to the wheel brakes alone that will help in this case, but as an automotive engineer for decades (that
was assigned to foundation brakes for a short time) and a GMC owner for a dozen years, my educated guess would be "Not Much if Any".

Why does geography matter?
About 30 years ago we were on one of our regular trips the east coast to make appearances with family. I had just redone all the brakes of the VW
diesel. We popped over the top of a hill east of Pittsburgh on RT-30 and then I saw the sign that said, "Trucks use low gear next 7 miles"
Too Late... Diesels do not engine brake because they have no throttle plate. I pulled every trick I had in my bag to try to hold the speed down, but
ended up on the brakes enough so the brand new disks were blue and there was smoke coming out at the bottom of the hill. We let the kids play on the
grass for about 15 minutes (until I could not feel the heat coming off the disks). I replaced those disks and pads again when we got home.

I have avoided that road in the coach. I did add the electric vacuum pump some time back.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit

 

[Ken B]

> Ken,
>
> Will installing the larger rear wheel cylinders have any effect on the braking when braking boost is lost? Does is help or hurt in that
> situation.
>
> Thanks,
>
> -Dave
> Near Pittsburgh
> 1978 Transmode

Not really. What it does is apply a little more pressure against the middle axle shoes as compared to the rear axle shoes. On heavy braking the rear
axle tends to shift some of the weight to the middle axle. So we are trying to brake a little heavier on the middle.

--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

 

[dave stragand1]

Thanks, Matt.

I do plan on installing the composite Ford pump for those very reasons
and the instructions folks have posted are wonderful. On the cars we
have restored, we always focus on the following things first: stopping,
steering, wheels have to stay on, and it can't catch on fire or explode.
The way we figure it, if those four things are good, you can deal with
anything else later. I'll be adding the larger cylinders to our
shopping list.

I believe I know that section of road. I love Rt. 30, the old Lincoln
Highway, but as "the first highway", it's not a modern road by any
means. Did you see the huge section that just collapsed?
https://www.youtube.com/watch?v=gZqKzNL202M

Thanks!

-Dave
1978 Transmode, near Pittsburgh

-----Original Message-----
From: Gmclist [mailto:gmclist-bounces] On Behalf Of Matt
Colie
Sent: Monday, April 16, 2018 8:49 AM
To: gmclist
Subject: Re: [GMCnet] Drum Brakes

> Ken,
>
> Will installing the larger rear wheel cylinders have any effect on the
braking when braking boost is lost? Does is help or hurt in that
> situation.
>
> Thanks,
>
> -Dave
> Near Pittsburgh
> 1978 Transmode

Dave,

This is one of those times when geography matters. I will get back to
that.

Something for you to try is:
Find a big open area.
Get the coach rolling, and shut the engine down.
Put one short jab on the brake pedal to blow the vacuum in the booster.
Now - see if you can stop the coach before Thursday.......

With no or little assist from the booster (you get only one try and not
the two you have been told), it is very difficult to stop a 12K# coach.
For
this reason, the first thing you should consider adding is some back-up
vacuum system. Be it electric or just a HUGE reservoir, where you live
I
would consider this essential to survival.

I can't tell you if there is any modification to the wheel brakes alone
that will help in this case, but as an automotive engineer for decades
(that
was assigned to foundation brakes for a short time) and a GMC owner for
a dozen years, my educated guess would be "Not Much if Any".

Why does geography matter?
About 30 years ago we were on one of our regular trips the east coast to
make appearances with family. I had just redone all the brakes of the
VW
diesel. We popped over the top of a hill east of Pittsburgh on RT-30
and then I saw the sign that said, "Trucks use low gear next 7 miles"
Too Late... Diesels do not engine brake because they have no throttle
plate. I pulled every trick I had in my bag to try to hold the speed
down, but
ended up on the brakes enough so the brand new disks were blue and there
was smoke coming out at the bottom of the hill. We let the kids play
on the
grass for about 15 minutes (until I could not feel the heat coming off
the disks). I replaced those disks and pads again when we got home.

I have avoided that road in the coach. I did add the electric vacuum
pump some time back.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit

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Unsubscribe or Change List Options:
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[Jim Hupy]

Anything you do to the rear brakes relative to drum brakes, keep in mind
that it is a siamese system. All 4 drums share the exact same fluid
pressure. The different sized wheel cylinders somewhat lessens the braking
effort on the rear/rear brakes and helps prevent rear tires from locking up
and flat spotting. This is caused from weight transfer from rear to front,
thus unloading the rear/rear brakes upon heavy braking.
A better use of that weight transfer is through the Reaction Arm
braking system. It uses a floating brake and torsion bar system to transfer
rotational forces into downward forces on the rear of the coach. Several
systems out there, both drum and disc. They all work.
I consider the top of the line to be Manny T's 1 ton front end
conversion with 11" brake rotors, combined with the Chuck Algur disc brake
reaction arm coupled with cross frame torsion bar rear suspension. That
setup will stop a GMC as well as modern automobiles, and have the ease of
servicing of a all disc brake system. Easy to check remaining lining also.
Lots of differing opinions on this, so be advised.
Jim Hupy
Salem, Or
78 GMC ROYALE 403

> > Ken,
> >
> > Will installing the larger rear wheel cylinders have any effect on the
> braking when braking boost is lost? Does is help or hurt in that
> > situation.
> >
> > Thanks,
> >
> > -Dave
> > Near Pittsburgh
> > 1978 Transmode
>
>
> Not really. What it does is apply a little more pressure against the
> middle axle shoes as compared to the rear axle shoes. On heavy braking the
> rear
> axle tends to shift some of the weight to the middle axle. So we are
> trying to brake a little heavier on the middle.
>
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[johnny]

Let's not forget here, the amount of braking front to rear is somewhat more determined by the transfer of weight when stopping, as opposed to the
actual value of that weight. That being said, my experience has been if you keep the rears from premature lockup you'll get shorter stopping
distances. You can do this by installing any of the several kits which float the backing plates like a motorcycle - they're usually called 'reaction
arms'. I've only owned drum rears on my coaches with the arms. They seem to stop as well as the rear disks, although I suspect in the mountainous
parts of the country the disks would be less prone to fading if you run long downgrades and don't know how to properly keep the coach speed under
control.

--johnny
--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased