Home » Public Forums » GMCnet » Machining Brake Drums (Machining Brake Drums)
| Machining Brake Drums [message #361738] |
Wed, 13 January 2021 17:55  |
Ken M
Messages: 32
Registered: December 2019
Location: Redding, CA
Karma: 0
|
Member |
|
|
I'm working on my brakes - new shoes, springs, cylinders, replacing rubber lines, etc. One of my drums has some pretty good scoring grooves in it. No telling how that happened. Does anyone have the specs for how much a factory drum can be turned in order to get rid of the grooves. I'd like to drop it off with the local brake machinist. I just don't know what specs to provide them... Anyone?
Ken
1975 - 26’ Eleganza II
Unsure of what upgrades may have been done. I'm working on sorting that out in the coming months.
Ken Morefield - Redding, CA
|
|
|
|
| Re: [GMCnet] Machining Brake Drums [message #361739 is a reply to message #361738] |
Wed, 13 January 2021 18:01  |
Bruce Hart
Messages: 1500
Registered: October 2011
Location: La Grange, Wyoming
Karma: 5
|
Senior Member |
|
|
Specs are on the drum. 11.09"
On Wed, Jan 13, 2021 at 4:56 PM Ken Morefield via Gmclist <
gmclist@list.gmcnet.org> wrote:
> I'm working on my brakes - new shoes, springs, cylinders, replacing rubber
> lines, etc. One of my drums has some pretty good scoring grooves in it.
> No telling how that happened. Does anyone have the specs for how much a
> factory drum can be turned in order to get rid of the grooves. I'd like to
> drop it off with the local brake machinist. I just don't know what specs
> to provide them... Anyone?
>
> Ken
> --
> 1975 - 26’ Eleganza II
> Unsure of what upgrades may have been done. I'm working on sorting that
> out in the coming months.
> Ken Morefield - Redding, CA
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Bruce Hart
1976 Palm Beach
Milliken, Co
GMC=Got More Class
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
Bruce Hart
1976 Palm Beach
1977 28' Kingsley
La Grange, Wyoming
|
|
|
|
| Re: Machining Brake Drums [message #361740 is a reply to message #361738] |
Wed, 13 January 2021 18:59 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
|
Senior Member |
|
|
Yes all drums have the max allowable internal diameter stamped usually on the edge. Keep in mind as you approach that size, they will fade sooner (less mass) and warp easier if you drive aggressively.
John Lebetski
Woodstock, IL
77 Eleganza II
|
|
|
|
|
|
| Re: [GMCnet] Machining Brake Drums [message #361745 is a reply to message #361740] |
Wed, 13 January 2021 23:33 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
|
Senior Member |
|
|
And, as I learned on a '39 Olds in '54, the drum can split, leaving you
with no brakes. I was 16 yo when I bought the Olds for $50. My Dad
insisted that we get the brakes & steering up to par before I drove it.
That included having the drums turned at the local machine shop. Almost
the first stop sign my teenage self and best buddy came to, doing probably
'way more than the speed limit, I had to do the teen-stop for the sign and
the city bus on the cross street. When I got on the brakes, nothing
happened before the pedal hit the floorboard. I managed to swerve around
the corner and miss the bus. The curb finally stopped us. The shop had
over-turned the drums, allowing one of them to split all the way around the
circumference and across the freed band.
Needless to say, I've been very careful about turned drums for the past 66+
years!
Ken H.
On Wed, Jan 13, 2021 at 7:59 PM John R. Lebetski via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Yes all drums have the max allowable internal diameter stamped usually on
> the edge. Keep in mind as you approach that size, they will fade sooner
> (less mass) and warp easier if you drive aggressively.
> --
> John Lebetski
> Woodstock, IL
> 77 Eleganza II
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
|
|
|
|
| Re: Machining Brake Drums [message #361761 is a reply to message #361738] |
Thu, 14 January 2021 16:54 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
|
Senior Member |
|
|
Yall can shame me but I never turn discs or drums. Any scoring is concentric anyway, so the puck or shoe quickly takes a set to the grooves. Anything grooved beyond the machining limit - .0625 or so - needs to be replaced anyway.
--johnny
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
|
|
|
|
| Re: [GMCnet] Machining Brake Drums [message #361764 is a reply to message #361761] |
Thu, 14 January 2021 17:07 |
Rob
Messages: 651
Registered: November 2013
Location: Victoria, BC
Karma: 3
|
Senior Member |
|
|
I'm with you - I don't think I've ever machined or resurfaced rotors or drums, regardless of the vehicle...
Rob
76 Royale Twin Beds, Dry Bath
Victoria, BC
> On Jan 14, 2021, at 2:54 PM, Johnny Bridges via Gmclist wrote:
>
> Yall can shame me but I never turn discs or drums. Any scoring is concentric anyway, so the puck or shoe quickly takes a set to the grooves.
> Anything grooved beyond the machining limit - .0625 or so - needs to be replaced anyway.
>
> --johnny
> --
> 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
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
Rob -
Victoria, BC -
76 Royale - Rear Twins/Dry Bath
|
|
|
|
| Re: [GMCnet] Machining Brake Drums [message #361767 is a reply to message #361764] |
Thu, 14 January 2021 19:01 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
|
Senior Member |
|
|
Many, many, NEW BRAKE ROTORS are seriously out of true as well as
concentricity. After they are bolted onto your hubs, they should ALWAYS be
checked with a dial indicator. If their runout is greater than .003" they
should be trued. Unless you just happen to like pulsating pedals and
excessive wear on pads, calipers, and front wheel bearings. Then, slap 'em
together and forget about it.
Jim Hupy
Salem, Oregon
On Thu, Jan 14, 2021, 3:08 PM Rob via Gmclist
wrote:
> I'm with you - I don't think I've ever machined or resurfaced rotors or
> drums, regardless of the vehicle...
>
> Rob
> 76 Royale Twin Beds, Dry Bath
> Victoria, BC
>
>> On Jan 14, 2021, at 2:54 PM, Johnny Bridges via Gmclist gmclist@list.gmcnet.org> wrote:
>>
>> Yall can shame me but I never turn discs or drums. Any scoring is
> concentric anyway, so the puck or shoe quickly takes a set to the grooves.
>> Anything grooved beyond the machining limit - .0625 or so - needs to be
> replaced anyway.
>>
>> --johnny
>> --
>> 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
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
|
|
|
|
| Re: Machining Brake Drums [message #361788 is a reply to message #361738] |
Fri, 15 January 2021 07:51 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
|
Senior Member |
|
|
And actually, to properly true a disc, it should be trued on the vehicle. Which we used to do with the racer. Takes some 'doing' because you need a rigid grinder stand and a way to spin the disc.
--johnny
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
|
|
|
|
| Re: Machining Brake Drums [message #361799 is a reply to message #361738] |
Fri, 15 January 2021 19:48 |
Ken M
Messages: 32
Registered: December 2019
Location: Redding, CA
Karma: 0
|
Member |
|
|
Thanks all. I did confirm the specs are stamped right on the rotor. Swung by the machine shop and he said the grooves are too deep to get out. He could clean them up some, but they won’t be perfect. It looks like way back on a former lifetime, a previous owner wore the shoe down to the rivets. Just the one drum. Maybe it was maladjusted... so leave it as is, buy a new drum, or machine it concentric and run with it...
1975 - 26’ Eleganza II
Unsure of what upgrades may have been done. I'm working on sorting that out in the coming months.
Ken Morefield - Redding, CA
|
|
|
|
| Re: Machining Brake Drums [message #361800 is a reply to message #361799] |
Fri, 15 January 2021 20:45 |
Rick Staples
Messages: 126
Registered: May 2014
Location: Johnstown, Colorado, USA
Karma: -1
|
Senior Member |
|
|
Ken,
Jim K has replacement drums. I put 4 on years ago. Recommend truing on a brake lathe pilotted on the bearing races after bolting on.
My 2¢,
Rick Staples
Rick Staples, '75 Eleganza, Johnstown, CO
"Advice is a dangerous gift, even from the Wise to the Wise, and all paths may run ill." -Tolkien
|
|
|
|
|
|
| Re: Machining Brake Drums [message #361848 is a reply to message #361800] |
Tue, 19 January 2021 11:25 |
uprooted
Messages: 72
Registered: December 2019
Location: Hilliard, OH
Karma: 0
|
Member |
|
|
+1 bought new drums from applied because on of mine had a deep groove. Did have to get them trued. I did notice they were lighter than the OEM. Is this a consideration? I put the new, lighter drums on the middle axle (because hey, they're new) and the original heavier drums on the rear. Wondering now if I should have done that the other way with the old drums with more mass up front due to increased braking work that is done / more heat to be dissipated
Corey P /
Hilliard, OH /
1974 Glacier 26' /
3.70 FD /
ION Wheels
|
|
|
|
|
|
| Re: Machining Brake Drums [message #361921 is a reply to message #361738] |
Fri, 22 January 2021 10:13 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
|
Senior Member |
|
|
We had something like that at Mac's for the racer, Mac (McCune) fabricated it after looking at what the Honda shop was using.
--johnny
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
|
|
|
|
Goto Forum:
Current Time: Sat May 25 18:41:46 CDT 2024
Total time taken to generate the page: 1.76447 seconds
|
GMCforum
Search
Help
Register
Login
Home
