'70 Drum Brakes; when is rebuilding necessary? what should be done to optimize perfor - The 1947 - Present Chevrolet & GMC Truck Message Board Network

darkone · 08-02-2011, 02:06 AM

hey all, i dont know much about drum brakes, but im tearing all mine open for a necessary cleaning following my sandblasting. ive air blasted, and brake cleaner'd them, but i dont know how to identify if anything needs to be done to keep them in top notch shape. what should i look for, and what can I do to make sure sticking is not a problem? any help appreciated. thanks in advance!

whitelightnin92 · 08-02-2011, 02:45 AM

really for the pice it is to rebuild them, i would buy the shoes, wheel cylinders and hardware kit that way theyre completely new. personally i wouldnt want to keep drums on the front. im not going to tell you that drums are no good and you need discs tho.

fastwillie 696969 · 08-02-2011, 02:51 AM

this might help ya save it

mrein3 · 08-02-2011, 10:12 AM

I'm assuming you are talking about front drum brakes. To optimize performance, take off the front drums and install disk brakes.

If you are dead set on the drums, I would replace the shoes, replace the hardware kit, replace the wheel cylinder, and have the drums turned.

While you are in there this far I'd inspect and replace if necessary the wheel bearings.

Then I would put it all back together and make sure ALL the old brake fluid is flushed out.

After everything is all bled, adjust them to spec.

Then do the rears. New hardware, new shoes, turns drums, replace wheel cylinders, and make sure all the old brake fluid is flushed out. Button it up and adjust the shoes to spec.

GASoline71 · 08-02-2011, 11:19 AM

Don't be suprised if you go have the drums turned and they tell you they are out of spec for thickness and you'll need new ones.

But for "optimum performance", a disc brake conversion would be best.

Gary

1970 Bowtie · 08-02-2011, 12:25 PM

I rebuilt all 4 wheels on mine last year and they work fine for me.You just have to remember they are drums and not disc so you have to allow for more stopping distance.As all have stated above replacing the shoes,wheel bearings,wheel cylinders,hardware kit and turning the drums.You should also replace the brake hoses on all 4 wheels as these are known to deteriorate and collapse under braking.But if you have the money disc brakes on all 4 corners is the way to go.

darkone · 08-02-2011, 01:40 PM

what do you guys mean by "turning the drums"?

slikside · 08-02-2011, 01:55 PM

"Turning" refers to machining the surface of the drum that contacts the pad on your brake shoes. To achieve optimum performance, a completely clean, smooth, and uniform surface of the drum is necessary. It takes a metal lathe to do it. But you must have sufficient material left on the drum, so that when turning is complete, you still have a drum within minimum tolerance.

darkone · 08-02-2011, 02:40 PM

what should the min. thickness of the existing drum be in order to turn the drum?

slikside · 08-02-2011, 02:49 PM

I can't say, but any place that can turn your drums (brake shops, some parts stores, etc.) will most likely have the specs.

GASoline71 · 08-02-2011, 02:53 PM

The specs are cast into the drum...

Gary

PanelDeland · 08-02-2011, 05:16 PM

I would say,just replace the wheel bearings and seals.Since you blasted,there's probably sand (or media) in the bearings.If there is,no need to pull them twice.The drums will probably have to be turned.New shoes and wheel cyl.
You should probably price all the parts and see if it's not a better value to go ahead and do the disc swap.

cdowns · 08-02-2011, 05:43 PM

if you could find a really old mechanic that knows performance drum brakes and has a setup the shoes can b radiused for full contact on the drums for maximum performance

1972RedNeck · 08-02-2011, 06:08 PM

Quote:

Originally Posted by GASoline71

But for "optimum performance", a disc brake conversion would be best.

Gary

Why would they be better? Disc brakes take more PSI than drum brakes.

long69 · 08-02-2011, 06:36 PM

i'm gunna lay this out there, first stop for first stop drums are as good as disks. after that first hard brake without a long cooling off period disks have it all over drums.
do i have drums-yes do i want disks-YES.
back to the question- for my money- and it doesn't cost a thang- the most important thing is make sure they are adjusted properly.

68gmsee · 08-02-2011, 07:46 PM

I just did a complete drum brake job on my 68 GMC. Unbelievable difference!

This is repetitous since it's all been mentioned above but here's what I replaced on mine: (total cost about $250)

New shoes -front and back.
New brake spring kit (4)
New hoses. Three- 2 in front and 1 on the passenger side of the rear axle.
Had the drums turned (IIRC, $7 each)
New inner and outer bearings and seals.
All brake cylinders.

Things you will also need:
Wheel bearing grease and at least 3 cans of brake cleaner for insuring everything is clean. Also look up how to pack the bearings if you're not familiar with the procedure.

Brake adjusting tool (A screw driver will do in a pinch).
Brake spring install tools. (a pair of vise grips and duck bills pliars will do in a pinch)

Plan on the whole weekend. First day to get everything together and having the drums turned. Second day for the actual work.

And be sure and do only one side at a time so you can refer to the other when reinstalling. Take pics also, just to be on the safe side.

fastwillie 696969 · 08-02-2011, 07:51 PM

Quote:

Originally Posted by cdowns

if you could find a really old mechanic that knows performance drum brakes and has a setup the shoes can b radiused for full contact on the drums for maximum performance

he would have to be real old and to find one with re arch machine LOL

ed2552 · 08-04-2011, 02:25 PM

I rebuilt the drums on our 67 this spring and replaced the master cylinder, and while it's no disc setup, it stops plenty fine for an old truck. If your truck is a daily driver I HIGHLY recommend discs, but if you just drive it for fun, the drums will work fine too.

GASoline71 · 08-04-2011, 02:39 PM

Quote:

Originally Posted by 1972RedNeck

Why would they be better? Disc brakes take more PSI than drum brakes.

What does more PSI got to do with it? Don't see a lot of true performance rigs with 4 corner drums on them do you?

Stock rigs with a beefed up engine and a few go fast goodies... sure.

Gary

MARKDTN · 08-04-2011, 04:24 PM

Quote:

Originally Posted by mrein3

I'm assuming you are talking about front drum brakes. To optimize performance, take off the front drums and install disk brakes.

If you are dead set on the drums, I would replace the shoes, replace the hardware kit, replace the wheel cylinder, and have the drums turned.

While you are in there this far I'd inspect and replace if necessary the wheel bearings.

Then I would put it all back together and make sure ALL the old brake fluid is flushed out.

After everything is all bled, adjust them to spec.

Then do the rears. New hardware, new shoes, turns drums, replace wheel cylinders, and make sure all the old brake fluid is flushed out. Button it up and adjust the shoes to spec.

I agree-discs are much easier to work on. The cost of the swap using 73-87 stuff is not that much. That's what I would do.

08-02-2011, 02:06 AM	#1
darkone Registered User Join Date: Sep 2010 Location: none Posts: 239	'70 Drum Brakes; when is rebuilding necessary? what should be done to optimize perfor hey all, i dont know much about drum brakes, but im tearing all mine open for a necessary cleaning following my sandblasting. ive air blasted, and brake cleaner'd them, but i dont know how to identify if anything needs to be done to keep them in top notch shape. what should i look for, and what can I do to make sure sticking is not a problem? any help appreciated. thanks in advance!

08-02-2011, 02:45 AM	#2
whitelightnin92 Registered User Join Date: Dec 2009 Location: Greenwood, DE Posts: 72	Re: '70 Drum Brakes; when is rebuilding necessary? what should be done to optimize pe really for the pice it is to rebuild them, i would buy the shoes, wheel cylinders and hardware kit that way theyre completely new. personally i wouldnt want to keep drums on the front. im not going to tell you that drums are no good and you need discs tho. __________________ 06 ECSB 4X4 L33 HO 3.73s 15.56@89.9 STOCK 92 K1500 TBI350vortec(too much to list) 69 C10 short fleetside(under construction) 72 C10 short stepside(almost driveable)

08-02-2011, 02:51 AM	#3
fastwillie 696969 ~Rest In Peace~ Join Date: May 2005 Location: CALIFORNIA NOR CAL Posts: 9,707	Re: '70 Drum Brakes; when is rebuilding necessary? what should be done to optimize pe this might help ya save it Attached Images __________________ is it fast ? it has a lighting bolt donut? B___H please, I can remove 90% of your so called "beauty" with a kleenex

08-02-2011, 10:12 AM	#4
mrein3 Registered User Join Date: Feb 2000 Location: Center City, MN, USA Posts: 3,253	Re: '70 Drum Brakes; when is rebuilding necessary? what should be done to optimize pe I'm assuming you are talking about front drum brakes. To optimize performance, take off the front drums and install disk brakes. If you are dead set on the drums, I would replace the shoes, replace the hardware kit, replace the wheel cylinder, and have the drums turned. While you are in there this far I'd inspect and replace if necessary the wheel bearings. Then I would put it all back together and make sure ALL the old brake fluid is flushed out. After everything is all bled, adjust them to spec. Then do the rears. New hardware, new shoes, turns drums, replace wheel cylinders, and make sure all the old brake fluid is flushed out. Button it up and adjust the shoes to spec. __________________ '70 cab, '71 chassis, 383, TH350, NP205. '71 Malibu convertible '72 Malibu hard top Center City, MN

08-02-2011, 12:25 PM	#6
1970 Bowtie It's all in the timing Join Date: May 2009 Location: Lake Mary,Florida Posts: 600	Re: '70 Drum Brakes; when is rebuilding necessary? what should be done to optimize pe I rebuilt all 4 wheels on mine last year and they work fine for me.You just have to remember they are drums and not disc so you have to allow for more stopping distance.As all have stated above replacing the shoes,wheel bearings,wheel cylinders,hardware kit and turning the drums.You should also replace the brake hoses on all 4 wheels as these are known to deteriorate and collapse under braking.But if you have the money disc brakes on all 4 corners is the way to go. __________________ The Dude Abides. ---------------------- I aint sayin, I'm just sayin.

08-02-2011, 01:40 PM	#7
darkone Registered User Join Date: Sep 2010 Location: none Posts: 239	Re: '70 Drum Brakes; when is rebuilding necessary? what should be done to optimize pe what do you guys mean by "turning the drums"?

08-02-2011, 01:55 PM	#8
slikside Registered User Join Date: Jun 2010 Location: San Diego Co. Posts: 1,176	Re: '70 Drum Brakes; when is rebuilding necessary? what should be done to optimize pe "Turning" refers to machining the surface of the drum that contacts the pad on your brake shoes. To achieve optimum performance, a completely clean, smooth, and uniform surface of the drum is necessary. It takes a metal lathe to do it. But you must have sufficient material left on the drum, so that when turning is complete, you still have a drum within minimum tolerance.

08-02-2011, 02:40 PM	#9
darkone Registered User Join Date: Sep 2010 Location: none Posts: 239	Re: '70 Drum Brakes; when is rebuilding necessary? what should be done to optimize pe what should the min. thickness of the existing drum be in order to turn the drum?

08-02-2011, 02:49 PM	#10
slikside Registered User Join Date: Jun 2010 Location: San Diego Co. Posts: 1,176	Re: '70 Drum Brakes; when is rebuilding necessary? what should be done to optimize pe I can't say, but any place that can turn your drums (brake shops, some parts stores, etc.) will most likely have the specs.

08-02-2011, 05:16 PM	#12
PanelDeland I am a Referee of life. Join Date: Jun 2000 Location: Greensboro N.C. Posts: 13,993	Re: '70 Drum Brakes; when is rebuilding necessary? what should be done to optimize pe I would say,just replace the wheel bearings and seals.Since you blasted,there's probably sand (or media) in the bearings.If there is,no need to pull them twice.The drums will probably have to be turned.New shoes and wheel cyl. You should probably price all the parts and see if it's not a better value to go ahead and do the disc swap. __________________ The 47-present Chevrolet and GMC Truck Message Board Network,it's owners,moderators,members,and associates of any type should not be held responsible for my opinion. You can't fix stupid,not even with duct tape. "My appearance is due to the fact that "GOD" does punish you for having too much fun!" Barrett-Jackson has perfected alchemy,they make rust into gold! "You can lead a horse to water but you can't saddle a duck" "Cleverly disguised as a 'Responsible Adult' "Sometimes your Knight in shining armor is just a retard in tinfoil"

08-02-2011, 05:43 PM	#13
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: '70 Drum Brakes; when is rebuilding necessary? what should be done to optimize pe if you could find a really old mechanic that knows performance drum brakes and has a setup the shoes can b radiused for full contact on the drums for maximum performance __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY

08-02-2011, 06:36 PM	#15
long69 Registered User Join Date: Oct 2006 Location: lost angeles Posts: 159	Re: '70 Drum Brakes; when is rebuilding necessary? what should be done to optimize pe i'm gunna lay this out there, first stop for first stop drums are as good as disks. after that first hard brake without a long cooling off period disks have it all over drums. do i have drums-yes do i want disks-YES. back to the question- for my money- and it doesn't cost a thang- the most important thing is make sure they are adjusted properly.

08-02-2011, 07:46 PM	#16
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: '70 Drum Brakes; when is rebuilding necessary? what should be done to optimize pe I just did a complete drum brake job on my 68 GMC. Unbelievable difference! This is repetitous since it's all been mentioned above but here's what I replaced on mine: (total cost about $250) New shoes -front and back. New brake spring kit (4) New hoses. Three- 2 in front and 1 on the passenger side of the rear axle. Had the drums turned (IIRC, $7 each) New inner and outer bearings and seals. All brake cylinders. Things you will also need: Wheel bearing grease and at least 3 cans of brake cleaner for insuring everything is clean. Also look up how to pack the bearings if you're not familiar with the procedure. Brake adjusting tool (A screw driver will do in a pinch). Brake spring install tools. (a pair of vise grips and duck bills pliars will do in a pinch) Plan on the whole weekend. First day to get everything together and having the drums turned. Second day for the actual work. And be sure and do only one side at a time so you can refer to the other when reinstalling. Take pics also, just to be on the safe side.

08-04-2011, 02:25 PM	#18
ed2552 Registered User Join Date: Jan 2007 Location: Charles City IA Posts: 1,626	Re: '70 Drum Brakes; when is rebuilding necessary? what should be done to optimize pe I rebuilt the drums on our 67 this spring and replaced the master cylinder, and while it's no disc setup, it stops plenty fine for an old truck. If your truck is a daily driver I HIGHLY recommend discs, but if you just drive it for fun, the drums will work fine too. __________________ '67 C20, Under the Knife!, LWB, Eaton HO-52, Rear Coil Springs 72' GMC C2500, 350, TH400(?), Dana 60 '67 K10 4-spd., 305, SM465, Dana 44, 12 Bolt, RUST! '65 C60 292, 4 spd, 2 spd Rearend, 15' Grain Box, MINT! 09 Yukon Denali 82k Miles 6.2L/6A

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