Home » Public Forums » GMCnet » Turning/resurfacing the rear drums
| Turning/resurfacing the rear drums [message #235588] |
Thu, 09 January 2014 10:29  |
An87ttype
Messages: 157
Registered: September 2012
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Is there a spec for how much the drums can be cut? Mine are a little out of round and I'm hoping they can just be resurfaced. I have not found any measuments or whether or not it should be attempted. Thanks all...
1975 Eleganza II
Hudson Valley NY
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| Re: [GMCnet] Turning/resurfacing the rear drums [message #235605 is a reply to message #235600] |
Thu, 09 January 2014 11:46  |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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I only have them turned if they are out of round. If scoring is light and
circumferential, I rough them up with 60 grit, clean the heck out of them
with brake kleen, and dry rags. If scoring is deep, like from a broken
brake spring or rivets, only cure for that is replacement. I keep the same
diameter drums in pairs across the coach, not the same side. Just what I
do. Brakes are nothing to "CHEAP OUT" on. Fix them right, your life or
someone else's might well depend on it.
Jim Hupy
Salem, Or
78 GMC Royale 403
On Jan 9, 2014 9:36 AM, "Larry" <weidnerl@wwt.net> wrote:
>
>
> An87ttype wrote on Thu, 09 January 2014 11:20
> > Found it. The max turning diameter is 11.060. Max discard 11.090
>
> I don't know what the Max "out of round" should be (ideal is perfectly
> round) but I'd be inclined not to turn them if you don't have to. They are
> a rare bird and expensive to replace. I know that some would not approve
> of this but when I did my brakes, I roughed up the surface of the drums
> good with a 40 grit emery cloth...or the roughest I could find, to assist
> the new shoes in break-in. That worked for me.
> Just what I did. Your milage may vary.
> --
> Larry :)
> 78 Royale w/500 Caddy
> Menomonie, WI.
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| Re: [GMCnet] Turning/resurfacing the rear drums [message #235610 is a reply to message #235605] |
Thu, 09 January 2014 12:13 |
Larry
Messages: 2875
Registered: January 2004
Location: Menomonie, WI
Karma: 10
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| James Hupy wrote on Thu, 09 January 2014 11:46 |
I only have them turned if they are out of round. If scoring is light and
circumferential, I rough them up with 60 grit, clean the heck out of them
with brake kleen, and dry rags. If scoring is deep, like from a broken
brake spring or rivets, only cure for that is replacement. I keep the same
diameter drums in pairs across the coach, not the same side. Just what I
do. Brakes are nothing to "CHEAP OUT" on. Fix them right, your life or
someone else's might well depend on it.
Jim Hupy
Salem, Or
78 GMC Royale 403
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Yup, pretty much the way I handle it. Had not thought of " I keep the same
diameter drums in pairs across the coach, not the same side." but good suggestion.
Larry 
78 Royale w/500 Caddy
Menomonie, WI.
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| Re: [GMCnet] Turning/resurfacing the rear drums [message #235639 is a reply to message #235605] |
Thu, 09 January 2014 17:21 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Jim,
I wonder it there are any shops out there that re-arc new shoes to match the turned drums?
I dated myself with that question didn't I? ;-)
Regards,
Rob M.
Sydney, Australia
-----Original Message-----
From: James Hupy
I only have them turned if they are out of round. If scoring is light and
circumferential, I rough them up with 60 grit, clean the heck out of them
with brake kleen, and dry rags. If scoring is deep, like from a broken
brake spring or rivets, only cure for that is replacement. I keep the same
diameter drums in pairs across the coach, not the same side. Just what I
do. Brakes are nothing to "CHEAP OUT" on. Fix them right, your life or
someone else's might well depend on it.
Jim
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] Turning/resurfacing the rear drums [message #235642 is a reply to message #235639] |
Thu, 09 January 2014 17:51 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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I know of one in my area. Salem Brake and Wheel. They won't touch asbestos
lining today though. Back before we knew better, they ground and arced the
stuff in the open air frequently. Son in law has the place now. His wife's
dad is my age. Ground the stuff without respirators for 35 years or so.
Mettalics & Ceramics too. Sure wouldn't do that myself. All environment
enclosed with hepa filtered air now.
Jim Hupy
Salem, Or
78 GMC Royale 403
On Jan 9, 2014 3:21 PM, "Robert Mueller" <robmueller@iinet.net.au> wrote:
> Jim,
>
> I wonder it there are any shops out there that re-arc new shoes to match
> the turned drums?
>
> I dated myself with that question didn't I? ;-)
>
> Regards,
> Rob M.
> Sydney, Australia
>
> -----Original Message-----
> From: James Hupy
>
> I only have them turned if they are out of round. If scoring is light and
> circumferential, I rough them up with 60 grit, clean the heck out of them
> with brake kleen, and dry rags. If scoring is deep, like from a broken
> brake spring or rivets, only cure for that is replacement. I keep the same
> diameter drums in pairs across the coach, not the same side. Just what I
> do. Brakes are nothing to "CHEAP OUT" on. Fix them right, your life or
> someone else's might well depend on it.
> Jim
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: [GMCnet] Turning/resurfacing the rear drums [message #235657 is a reply to message #235653] |
Thu, 09 January 2014 19:11 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Back in the era of drum brakes, it was very common to be able to purchase
extra thick riveted on brake lining. A competent brake repair business
would drill out the rivets on your old linings, clean up your existing
shoes, and rivet on oversized linings. Then after the drums had been turned
to remove the out of round or scoring or glazed hard spots in the them, a
careful measurement would give them the outside diameter of the finished
linings. After chamfering the appropriate ends of the new linings and
grinding them to fit the drums, you could reassemble the brakes. This
produced a very good stopping system for the day. No comparison to a good 4
wheel disc ABS system of today though. There is one very lucky aussie
shepherd alive today because I was able to stop in time yesterday with my
PT Cruiser on the way back from a lab test. Good brakes are the most
necessary mechanical system on a GMC.
Jim Hupy
Salem, OR
78 GMC Royale 403
On Thu, Jan 9, 2014 at 4:57 PM, Gary Berry <duallycc@gmail.com> wrote:
> Bert and Fay had a problem a number of years ago with drum brakes and not
> arcing the shoes. It caused them a ton of consternation while on a trip.
> The outcome was to have them arced. Maybe they will post about that
> experience once again for some of the young folks here...
>
> --
> Gary and Diana Berry
> 73 CL Stretch in Wa
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| Re: Turning/resurfacing the rear drums [message #235711 is a reply to message #235588] |
Fri, 10 January 2014 09:26 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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If you had your own brake lathe, you could cut as little as possible to get them round and then remeasure. Then is a keep or toss. Trying to tell a guy to cut as little as possible is tough as they usually wait on another customer while the lathe is doing it's thing. Hard to put the shavings back on. I have a spin balancer but a used tire machine and lathe are on the eBay wish list to keep it in house.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Turning/resurfacing the rear drums [message #235723 is a reply to message #235711] |
Fri, 10 January 2014 14:07 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Get a machinists lathe with a tool post, and take your discs/drums down with a tool post grinder rather than a tipped cutter. It will surprise you how much smoother the brake action is. We had one at Mac's which was actually used to ream the bushings on Lycoming flat motor crankshaft weights. Worked gret on the race car and race bikes as well as our drivers.
--johnny
________________________________
From: John R. Lebetski <gransport@aol.com>
To: gmclist@temp.gmcnet.org
Sent: Friday, January 10, 2014 10:26 AM
Subject: Re: [GMCnet] Turning/resurfacing the rear drums
If you had your own brake lathe, you could cut as little as possible to get them round and then remeasure. Then is a keep or toss. Trying to tell a guy to cut as little as possible is tough as they usually wait on another customer while the lathe is doing it's thing. Hard to put the shavings back on. I have a spin balancer but a used tire machine and lathe are on the eBay wish list to keep it in house.
--
John Lebetski
Chicago, IL
77 Eleganza II
Source America First
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Foolish Carriage, 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
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| Re: [GMCnet] Turning/resurfacing the rear drums [message #235758 is a reply to message #235674] |
Fri, 10 January 2014 19:46 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Even if you find someone who'll turn drums beyond the specified maximum
diameter, DON'T DO IT. My second car, a '39 Olds, in 1954, taught me that:
Before my Dad would let me drive it, he insisted that all the safety items
be rebuild, including having the drums turned and the new shoes arced.
Naturally, at 17, every stop sign was a challenge -- how close can you get
before stomping on the brakes and still stop before you get into the cross
street? About the 10th stop after the brakes were finished, My stop wasn't
-- and there was a city bus in the intersection ahead of me. SOMEHOW, I
managed to turn the corner instead of T-boning the bus; tire sidewalls
scuffing against the unoccupied curb was all that stopped me without
encountering something harder.
One of the drums was in two pieces: The solid face and the ring which had
separated from that and split axially. I don't know whether there was a
requirement for max. diameter specs in those days, but if there was, the
machine shop ignored it: There was just not enough metal left to withstand
teenage enthusiasm.
You probably would not be as lucky with a GMC.
JMHO,
Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI & EBL
www.gmcwipersetc.com
On Thu, Jan 9, 2014 at 9:46 PM, <roy@gmcnet.org> wrote:
>
>
> Robert Mueller wrote on Thu, 09 January 2014 15:21
> > Jim,
> >
> > I wonder it there are any shops out there that re-arc new shoes to match
> the turned drums?
> >
> > I dated myself with that question didn't I? ;)
> >
> > Regards,
> > Rob M.
>
> My experience with cars was if you buy cheap shoes the lining is thin and
> it is a poor fit in the drum. If you buy premium shoes the lining is much
> thicker and it is a much better fit in the drum. We are talking well used
> drums here.
> --
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] Turning/resurfacing the rear drums [message #235788 is a reply to message #235764] |
Sat, 11 January 2014 06:29 |
Burt and Faye curtis
Messages: 256
Registered: June 2012
Karma: 4
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Senior Member |
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Gary, and others,
you can still read about our saga by going to
gmcws.org/newsletter/index.html and then hitting on the Feb 2003
newsletter.
Bert and Fay (who is totally convinced about the importance of arcing brake
shoes now for our GMC)
On Fri, Jan 10, 2014 at 7:06 PM, Emery Stora <emerystora@mac.com> wrote:
> Gary
> You have a good memory. That was almost 12 years ago. That was way back
> in the Fall of 2002 at our GMCWS rally in Cody, WY.
> A few of us spent several hours working on their brakes It was initially
> felt that it must be the master cylinder. It was only later that we found
> out from them what the problem really was.
>
> Emery Stora
>
> On Jan 9, 2014, at 5:57 PM, Gary Berry <duallycc@gmail.com> wrote:
>
> > Bert and Fay had a problem a number of years ago with drum brakes and not
> > arcing the shoes. It caused them a ton of consternation while on a trip.
> > The outcome was to have them arced. Maybe they will post about that
> > experience once again for some of the young folks here...
> >
> > --
> > Gary and Diana Berry
> > 73 CL Stretch in Wa
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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