Cleaning and Adjusting Rear Drum Brakes

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The Critic

The Critic

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I often see in automotive repair advertisements that the shop will clean, lubricate and adjust your rear drum brakes when they do your normal front brake service.

What does this involve? I've never owned a vehicle with drum brakes, and haven't worked on one outside of auto class.

What do I adjust? What do I lubricate? Diagrams would be helpful.
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Thanks.
 
I'm guessing that they blow the brake dust out, lube the backing plate where the shoes make contact, and adjust the shoe/drum contact using the star adjuster, either beginning with the drum off or from the rear adjustment hole. IIRC, with the wheel off, there should be a slight drag when you attempt to rotate the drum and it should come to a stop within a turn or so. No one ever showed me the "proper" adjustment though.
 
You would find diagrams and pictures in the Holmes or Chilton repair manual that you are going to purchase.

Likewise with the inspection details already mentioned above. Plus, you'll find inspection criteria in that repair manual. The big inspection items for me are:

-Inspect the condition of the drum friction surface for extensive wear or grooves.

-Inspect the thickness of the shoe friction material. Rule of thumb is to have more than the thickness of the shoe steel backing.

-Inspect shoe friction material for evenness of wear end-to-end. The leading edge often wears more quickly.

-Inspect springs/clips for rust & wear.

-Inspect/lubricate accessible adjustor parts.

-Inspect/clean/exercise the bleeder valve.

-While you're under there with everything apart, have a good look at the brake lines and suspension bits.

Most important, don't blow out the brakes with compressed air!!! The dust is harmful to your lungs. Even if there isn't a single bit of asbestos in the dust there are many other things that are equally nasty. Use the spray liquid brake cleaner. I use about a can for each corner. Don't be shy with it, and be sure you have a drip pan under the drum.
 
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You could blow them out with compressed air, or use water sprayed from a pump up insecticide sprayer, or use spray brake clean.
When dry, inspect and lubricate.
I use synthetic wheel bearing grease. Some will take offense and tell you to use anti seize, but that is not a lubricant - it is for a different purpose.
On a drum brake, the shoes move a bit. Release the retaining clips and lube the little pads on the backing plate where the shoe slides - 3-4 of them on each side, and the pivot at the bottom, and where they are contacting the wheel cyl.
Any common spray lube can be used for the adjusting mechanism and P brake parts that move. Don't be a slob with any of the lubes - common sense is your best friend.
They should self adjust by normal driving or backing up and hitting the brakes several times [If everything is working correctly].
The only problem will be trying to stand up after being crouched down for a half an hour!
 
Drum brakes are a PITA. Thankfully only my Jeep has them. When ever I do anything to them, I pull both drums and work on one side at a time so I can refer to the other side.
 
A very good post going here. I plan to do this exact same job on my truck this weekend. Please if anyone has any more info to share I would greatly appreciate it..

Thanks
 
Jimmy, I think your sig is the main thing to remember. Drum brakes can be a PITA to work on if stuff is frozen together, but they do a good job if adjusted well.
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Just curious here you guys take the shoes off but dont adjust the adjuster when they go back on?? Seems like a waste of time?
 
I use silicone paste to lube the adjuster (chassis lube should work too), and antiseize to lube the shoe / backing plate contact points. I've used chassis grease before for the contact points, but it washed away in short order.

I set the adjuster so there is just enough slack to get the drum back on. Normal driving will get it to self-adjust to the final position. You certainly don't want to adjust it too tight... self adjustment only works in one direction.

Just about all drum systems are now servo type. The non-servo type does not have any self adjusting mechanism and has to be manually adjusted every so often. I haven't seen that design since my 85 Omni.
 
It's also a good thing to do to take a digital photo of the brakes either with a nice camera or maybe your cellphone before you start. If you're like me, if it's been more than ten minutes there's no guaranteeing I'll remember anything.

Lay your parts out on the ground in the same position as they came off. Be careful not to kick them.

Or, if you REALLY don't like drum brakes make sure all your newly purchased cars have four wheel discs.
 
I have to believe the real reason they do the "free" cleaning and adjustment of the rear brakes is to "drum" up more work/$$$$.

"Ma'am, this dust in your drum brake is an indication of advanced wear. Since you're putting new front brakes on, we recommend replacing the rears to keep your system safe and balanced"

Cha Chingggg$$$$$$$$$
 
Twice I have had mechanics switch left and right self adjustors on rear drum brakes which made them not work. You'd think it wouldn't be that hard to keep straight.
 
Probably the same stuff that corrodes the internal components. Perhaps 'washes away' is the wrong term, but in my experience the chassis grease doesn't last long and goes dry at the backing plate.
 
Drum brakes are certainly a pain to reline, however most rear disk brake systems cause far more maintenance work(pad life is extremely shortly, sliders & caliper piston seizure, etc). For most applications front disk/rear drum is still the best comprimise.
 
Thanks guys.

Newbie question, but does anyone have a diagram of a drum brake? It has been a while since I was in auto class.
 
they are fairly simplistic, but definitely not fun to work, since they don't need frequent service they are a bear to work on once everything is worn/brittle and covered in dust.

i always hose everythign down with brake cleaner and then begin.

i never mess around with reusing minor parts like springs and whatnot, just got to advance auto etc. and pick up a hardware kit, much easier that way.

and i also use the method of doing one side at a time, pictures and stuff are not always best.

about the only thing that i dislike is putting the parking brake mechanism back together because you need to remove the pin and install it on the new shoes.
 
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