How long do OEM brake drums last?

[LowMilesLesabre]

My Buick just reached 100,000 miles and has been treated very gingerly over its lifetime. No high-performance driving nor high-performance “stopping“. I just had it looked at and it appears that my rotors will need replacing due to corrosion (this is expected and not the gist of my question ). But as to my rear drums, they are not corroded to any great extent. At the shop where I had the brakes inspected, they measured them with callipers, and my drums were deemed to be worn down to the point where they are just shy of not being minimum Specs. My question for anyone who might like to chime in is this:

Is there such a thing as an average lifetime of brake drums on the rear of a chassis which were the original OEM factory drums? A quick search online suggests that drums can last anywhere from 150 to 200,000 miles. While the drums were off of my car, I noted that the shoes had virtually no grooves or indentations in them and have led a fairly gentle life, although the shoes themselves need to be replaced due to expected wear over more than 25 years. I don’t mind paying for replacement drums, but if I can keep my OEM drums and restore my car’s braking with the new shoes, is there any reason to replace the drums? I just find it hard to believe on a car that has been driven by elderly folk for most of its life to have the need for its drums be replaced at 100 K seems a bit odd. Note that when I have the shoes replaced, I will also have any hardware such as springs be replaced as well, but I would like to keep the drums unless there is a legitimate reason to replace them. Any thoughts would be appreciated.

 

[CarlB]

Without measuring your drums, we'd all be speculating. Any reason you are attached to these drums?

 

[GSCJR]

Without measuring your drums, we'd all be speculating.

+1, and with a brake drum gauge not a caliper.

 

[CourierDriver]

well this post is popular ,,,,,,,,,,,,,,,,,,,,,,,,,,,,I need a cold one,,lol

 

[eljefino]

So which spec? There's a "service replacement" spec and a "discard" spec. Sometimes shops are confused between the two, or deliberately conflate.

 

[CourierDriver]

Without measuring your drums, we'd all be speculating. Any reason you are attached to these drums?

now thats the smart thing to do,,,,

 

[JavierH19]

I changed my old rangers factory drums at around 280 something thousand if I remember right and I just figured it was time even though I didn't see any real reason or measure them. I just figured I'd replace them since they were still the originals and I was only changing the pads up until then. It's possible for those to be near their end if they were just cheap and thin from the start. But I wouldn't be surprised if the shop lied to get a chance to upcharge on the parts and add more labor.

 

[bdcardinal]

FWIW I bet a search of a junkyard will reveal a lot of factory drums still on vehicles.

 

[JeffKeryk]

Well, my 01 Tundra, 220K, is on it's original set... Guess it depends.

 

[nwjones18]

Well, my 01 Tundra, 220K, is on it's original set... Guess it depends.

Yeah they're borderline eternal unless something they're run with shoes metal to metal.. At least in my experience

 

[michaelluscher]

Did they measure them with any precision, or are they assuming based on mileage?
Here's the specs

 

[D60]

Just like w discs and pads, if I'm replacing shoes, I'll be replacing drums, or at least having them turned.

I'm not willing to risk a comeback from noise or performance complaints. And yeah, I've seen a drum shriek like a banshee -- but to be fair that was due to gear oil contamination.

That said, plenty of vehicles seem to be easy on shoes. A recent exception I learned (as confirmed by clinebarger) is GMT900 half-tons, which seem to mow through shoes surprisingly quickly.

 

[Reggaemon]

Usually what I have seen is drum brakes that will only be on the rear of a car will last forever because the auto adjusters get dirty and stop working.

 

[71Chevyguy]

I have one of these cars approaching 200k and replaced the drums simply because others were rounder than mine were. I did go the junk yard route, not because of cost, but many have said that Chinese replacements aren't very good. But honestly, if mine weren't out of round, they would still be good at 200k. I have not used any of the cheap replacements so I can not comment on differences there. But I did install powerstop shoes and they seem to work fine.

Also check your wheel cylinders, both of mine with this setup had the wheel cylinders seize in the bores and only work on the front side, didn't do much. They weren't leaking but were bad. Braking was MUCH better after replacing them of course. Some things just need to be replaced after 25 years due to age.

 

[ecotourist]

Interesting dimensions:
Discard at 8.909" diameter
Maximum refinish 8.92" diameter

You should discard at 8.909" but could machine out to 8.92". How does that work?

 

[D60]

Interesting dimensions:
Discard at 8.909" diameter
Maximum refinish 8.92" diameter

You should discard at 8.909" but could machine out to 8.92". How does that work?

I love how they get down to a single thou, like it's fine at 8.908, but at 8.909 it's scrap. I understand there has to be a threshold, but this feels ridiculous at three decimal places.

As for your question, I can only assume they're thinking you'll need more than 11 thou on diameter to clean it up. That's just about 5 thou on a side. Thus if you start at 8.909 you'll likely exceed 8.920 to get a decent pass.

Again, completely guessing there....

 

[paulo57509]

My father didn't have a drum lathe, but he did have an Ammco drum mic. He once explained to me about the discard/refinish limits but when you're 11 years old, nothing your parents tell you sinks in very deep.

 

[paulo57509]

Interesting dimensions:
Discard at 8.909" diameter
Maximum refinish 8.92" diameter

You should discard at 8.909" but could machine out to 8.92". How does that work?

I think numbers mean:

• If you mic the drum (as is) and it measures 8.909", throw it away and don't bother resurfacing.
• If you mic the drum and it measures < 8.909", break out the calculator to determine the maximum depth of cut that can be made and still be at (or under) the Maximum Refinish Diameter of 8.92".

You need the measurement of the drum, "as-is" to make any sense of the Discard and Maximum Refinish dimensions.

Q: Can the drum be resurfaced? Using the formula:

m + 2c < D​

m = diameter of drum "as-is"​

c = cut measurement​

D = discard dimension​

​

Example 1 - Given:

m = 8.800"​

D = 8.92"​

c = ?​

​

8.800" + 2c < 8.92"​

2c < 8.92" - 8.800"​

c < (8.92" - 8.800") / 2​

c < 0.060"​

​

The above example, the machinist can remove a maximum of 0.060". This depth cut is probably enough to ensure a good finish, and ensure roundness of the drum, and still be under Maximum Refinish dimension.

Example 2 - Given

m = 8.909" (discard diameter)​

D = 8.92"​

c = ?​

​

8.909" + 2c < 8.92"​

2c < 8.92" - 8.909"​

c < (8.92" - 8.909") / 2​

c < 0.006"​

​

A 0.006" depth of cut is probably not enough to provide a good fimish, or ensure roundness of the drum and still ensure that the drum is at or below the Maximum Refinish DIameter.

​

I now have a headache and need to find some Tylenol.

 

[ecotourist]

When I was young I replaced the shoes (for rear drums) on my '65 Comet. The drums had a fair size lip and I even had trouble getting the drums off. [You push a screw driver in through an inspection hole to release the star wheel so you can turn it backwards.] The internal drum surface was a bit irregular with ridges and grooves. They would have benefited from machining.

But having no money and little sense, I reasoned that the new shoes and drums would adapt to one another given a bit of time. So I left the drums as they were, put on new shoes and braked carefully for a week or so.

Those brakes worked just fine for the rest of the life of the car. Of course I never encountered an emergency braking situation while those shoes were new, so I don't know what would have happened. I can imagine all sorts of problems - too little contact area meaning little braking effect, asymmetrical braking between sides, etc.

I don't recommend this method (in fact I wouldn't do it today) but that's what I did. I'm always amazed by what we've done in the past and most of us survived.

 

[zzyzzx]

Yeah they're borderline eternal unless something they're run with shoes metal to metal.. At least in my experience

OP lives someplace where cars rust a lot. I suspect that might be the limiting factor there.