Hard or soft braking

What you also won't be able to check with those is bell mouthing of the drum. In fact, the only part you *may* be able to measure is the

*unworn* lip, if any. Used to use dedicated drum calipers, designed for the task.

Hi Xeno,

I appreciate greatly and agree with the "proper tools" advice from you and Steve, where I must also note though, that I hadn't "noticed" a problem with the general purpose tools in so much as you can get pretty deep with general purpose mics, particularly if you use a larger mic than one inch mic on rotors where the wear is pretty even in almost all cases I've seen.

Also, if you zoom into this photo I took long ago and look to the right, you'll see that the "lip" is pretty much almost perfectly taken into account by the stairstep shape of the inside jaws:

Still, I don't disagree with your main point of view which is that special purpose calipers and mics and dial gauges would be best for those of us who do all our own automotive work at home.

The tools are usually free, except for their storage, where I get high friction pads and shoes for a great price (around $25 to $50 or so an axle) and rotors/drums for about the same price per wheel, where I've seen people spend upwards of thousands of dollars for a four wheel brake job.

Given that I save hundreds, if not thousands of dollars by doing my own brakes, it wouldn't be a bad idea to purchase brake-intended tools for measuring runout, rotor thickness, and drum diameter.

Where do you purchase your brake-related measuring tools from?

Amazon "suggests" these for brake rotor inside diameter measurement: o Fowler 72-010-777 Drum and Rotor Measuring Kit

o Brake Drum and Rotor Measuring Kit w/Caliper

o iGaging 20" Brake Drum Caliper Gage Digital Electronic

o K-D Tools 3774 Digital Brake Rotor Gauge

o Central Tools 3M130 .300"-1.300" Brake Rotor Micrometer

And Amazon added this weird looking gauge for "resetting" brake drums: o AMPRO T71558 Brake Drum Resetting Gauge

Note I don't even know how to use that last tool, as I've never seen one.

When I was in the trade, I used the ones in my workplace. The college had all the gear I needed. These days I have sources where I can borrow such things as required.

It tells you what it does in the description. It measures clearance between the brake lining and the drum.

That doesn't explain how to use it, but that's OK as the way I do the shoe-to-drum clearance is I adjust that by a friction fit and then back it off a few notches, and then I engage the self adjusting mechanism once it's all put back together.

Luckily, nowadays, very few vehicles I've worked on have drum brakes, where that specific drum was on an SUV that went something like 180K miles on one set of rear shoes (and there was _still_ meat on those rear shoes but I replaced them anyway because I didn't want to have to take it apart again).

It's shocking, actually, how long the rear brake shoes lasted on that SUV, where I replaced the clutch twice in the time that I did the shoes just once, and that rear drum had plenty of meat left for another 180K miles.

BTW, do you radius grind brake shoes when fitting them to an oversized (worn or machined) drum.

Here is something for you to cogitate on. You have a drum that requires machining. You do that and it is now *oversize*. You now go out and buy a set of new shoes. What you will find now is that the diameter of the shoes no longer matches the diameter of the shoes. When you adjust the shoes up, as you describe above, the linings only contact the drum in a small section at the centre of the length of the lining. Both ends of the lining will not contact the drum. That means that, as you are bedding in your nice new brakes, only, say, 25% of the linings contact the drum. Guess what that does to brake efficiency?

There are 3 solutions to this issue.

The first is to radius grind the new shoes so that their arc matches the arc of the drum. Used one of these radius grinders in the 70s.

need to be sure the dust extraction and capture system works and it looks pretty absent on the video.

The second is to replace the drum rather than machining it. In fact, a lot of manufacturers don't recommend drum machining these days.

The third is to get new shoes with thicker (oversize) linings to match the larger diameter of the drum.

Some say all linings should be matched to the drum diameter - oversize or otherwise to ensure an efficient and rapid bed in. Like this one;

Anyway, just something more for you to think on.

Correction, ..... shoes no longer match the diameter of the drum.

I haven't cut a drum or rotor in a lot of years, in my area the rust kills them faster than the shoes or pads can eat them. I only know of one shop that still turns them and their machine gets powered on about 2 times a year. Same issue with calipers, if the vehicle is over a year old, forget trying the bleeder and 99% of the time the slides are stuck from rust. SOP in my place is pads and rotors unless they have really good coated rotors that haven't rotted away.

As for shoes, I've ground them a few times but generally they get replaced due to rot. Especially if they are drum in hat rotors used as parking brakes. Since maybe 1 in 5000 use them the shoes are generally rotted apart and the drum looks like it sat on the ocean floor for years.

Not shocking on many trucks and SUVs, unless they have weight in the rear the load sensing valve barely lets the rear brakes apply. I've seen many that the rear brakes were barely worn at 100K. Now on work trucks that had a load the results are much different.

I made a few drum and rotor tools over the years. Extended jaws for calipers and deep frames for mics. These days even the cheap digital one from harbor freight is better than most of the older tools that were sold back then.

BTW, is this about right for what you might think under "normal use" where I know there's no such thing as a defined normal use... but anyway...

a. The clutch lasted less than 100K miles (say, oh, about 80 or 90K). b. The rear shoes lasted less than 200K miles (say, about 180K or so). c. The front pads lasted less than 50K miles (say, oh, about 30 or 40K). d. The front rotors went about double the pads (about 75K miles or so). e. The rear drums are gonna last about double the shoes (about 350K).

While every "normal" is different, how do those estimates sound if someone were to ask you "how long" do these things last under normal use?

That depends entirely on how the person operates the vehicle and what the vehicle is. In city stop and go, you are going to use up the brakes and clutch faster than highway driving, usually by a large margin. However if you drive like one of my relatives you will wipe out the brakes far faster. She likes to drive fast, then climb on the brakes rather than down shift or use any engine braking at all. She goes through at least one full set of pads and rotors in about 30K or so. Calipers at every second swap.

Then there are cars like my wife has, it's AWD and has a VERY balanced braking system. It had all new brakes put on by the dealer when we bought it at 60K and it has 140K on it and the pads and rotors still look new. I'm going to change out the pads because the caliper pins stuck on one front and the inner pads in the rear hung up and let the rotor rust. All related to installer error.

With the description you have given of your driving style and road conditions you have I would say you did pretty good. However it wouldn't be hard to double the clutch life and front brakes on flatter terrain.

Understood. It's a 2WD suv driven by a relative as a daily drive on these roads:

Rough estimates for that 2wd SUV are (in increasing miles): o Tires <30K miles o Front pads <50K miles o Front rotors <75K miles o Clutch <90K miles o Rear shoes <200K miles o Rear drums <350K miles

Yes. The problem for the clutch is the terrain, and, this particular driver doesn't comprehend the concept of being gentle on the clutch either.

Even so, the hills eat the tires:

Xeno explained why in the past as 'camber scrub':

Which is an amazingly complicated set of affairs:

Resulting in wear of the front inside edge that you can't believe:

Which is palpable after even as little as a few hundred miles:

Hi Xeno, I love that you brought up points of additional points of finesse, which is, after all, what learning on rec.autos.tech is all about!

One thing I have observed, which I'm sure you'll understand, is that living in the Silicon Valley, where shop rates are commonly around $200 an hour, _any_ machining of basic parts isn't going to ever be cost effective.

As an example, when I replaced the flywheel of the SUV, the cost for machining it was almost the price of a brand new flywheel at the auto parts stores (but far less than a brand new dealer-supplied flywheel).

Even though the flywheel could have been machined, it wasn't worth it given the cost of labor here in the Silicon Valley.

I suspect machining shoes and drums would have the same economics, unless we bought the tools to do ourselves.

I think throwing away parts instead of machining them is kind of sad because we throw out a lot of useful parts simply because they're cheaper to replace than to machine.

Given that, on many cars, the disc is considered a wearing component just as much as the pads, machining is likely not intended. For sure, there are some marques where you cannot machine the discs at all. But then, replacement discs are inexpensive.

If the flywheel has hard spots, machining is not always successful. The cutting tool rides over the hard spots leaving high points. In these cases, surface grinding is the better/only option.

Yes, costs always figure into the equation.

If you have, or have access to, a lathe, you can do most machining yourself. It won't be as *efficient* as a dedicated brake machining tool but it will get the job done. I used to use these;

Very quick and efficient. Even at $200 per hour, I could make machining operations cost effective with this machine. If you had ever used one, you would know why.

That is the way of the world.