"Mark the relationship of the drum to the axle and remove the drum." - Why?


#1

Title says it all…this is a step listed in my manual for removing the drums on the rear brakes.



I can make some guesses, but why is it so important that the drum goes back on exactly the way it was? Isn’t it round? And if a bit out-of-round, I don’t see how changing which hole goes over which stud would change anything.

With a new drum (i.e. not putting the old drum back on) this would be a moot point right?



Just curious,

Jad


#2

Doesn’t make much sense to me, either.

And yes, the point is clearly moot if you are replacing the drums.


#3

A lot of automotive lore is urban legend stuff. Some of it finds it’s way into tech manuals…What make of model of vehicle is this procedure listed for?


#4

A 1997 Cavalier. Glad I’m not missing something incredibly obvious.

This is actually for my little brother’s Cavalier. He’s got an issue when, under light braking (3-5 MPH), the rear wheels will lock up. We weren’t sure if it was ABS induced, so we disabled the ABS but it still happened except with full lock instead of an ABS “stutter” lock up. This won’t happen when braking at high (or higher) speeds.

Is this a drum brake adjustment problem or something else? This vehicle doesn’t have a proportioning valve, at least not one that I can find. I noticed with the wheel and drum off (drum was a bear to get off!!) when my brother presses the brakes, it seems like only the shoe closest to the front of the vehicle moves out, the other one doesn’t move or barely moves. Is that normal operation? The shoes don’t seem unevenly or excessively worn. The drum does have some dark round marks on the inside, every inch or so, I’m guessing from that premature rear lock up.


#5

the idea was to keep the drum balanced to the axle, that is what was taught. I did this about 3 times but logic & common sense got the better of me and I deducted that the axle & drum where never balanced together when the car was built so I never did it again. I have never had a customer come back and say something was odd since I did not mark a witness point onthe drum/axle…


#6

Ahhh…Gotcha. I figured it was something like that but I couldn’t make sense out of it.

Any ideas on the rear wheel lock-up problem?


#7

Leaky wheel cylinders (brake fluid) usually visible with drum off, or grease seals if rear wheel drive which I guess the isn’t??


#8

It’s FWD…what should I see if the wheel cylinders are leaking? Everything was very black inside once the drum was off and a fair bit of dust came out. But I didn’t see any fluid…


#9

Sounds like one of the pistons is seized in that wheel cylinder, and the drum is heat damaged.


#10

If the brake hoses have deteriorated internally, the debris will prevent the brake fluid pressure from returning to zero when the brake pedal is released. The cure? Replace the brake hoses.
The wheel cylinder bores may be corroded and not allowing the wheel cylinder piston to return to rest position … at least, not quickly. The cure? Replace the wheel cylinder(s).


#11

Sounds like a complete rear brake job is needed then…ouch. No point in keeping the old shoes/drums on there after replacing the hoses and cylinders, in case there was any leakage on the linings.

Thanks all!


#12

Many Japanese imports use a peculiar screw to hold the drum in place…


#13

That’s two screws which one moves to the threaded holes in the brake drum to push the drum off. Too bad American cars never did that.


#14

Domestic drums have been pinned on with lock-rings which get discarded whenever the drums are removed and the drums are usually no problem to remove unless they are badly worn. The closer tolerance of the drum’s fit on the hub of Jap imports is quite tellling, though.


#15

Too bad American cars never did that.

I do not understand why they needed to. Using the 2 screws to push the drum off is not a superior design, just a different design.


#16

When you have to use a large 12" jawed puller to remove a brake drum, you’d be glad if it had the push screws. So, the idea is better. Not everyone has such a large puller.


#17

The reason I was given many years ago is that it’s to make sure the drum is aligned with the same stud the removed wheel assembly is supposed to be aligned with so the wheel and drum will mate back into the same position. The axle was actually irrelevant.


#18

The closer tolerance of the drum’s fit on the hub of Jap imports is quite tellling, though

There are two designs; hub vs lug centric. IMO, the hub centric designs are more prone to rusting in place and being harder to remove because they are so tightly toleranced to the hub. For example, I have two vehicles, both bought new, with about the same mileage and usage pattern. One is lug centric, the other hub. I had to cut the rotors off the hub centric car whereas the lug centric rotors practically fell off the other. BTW, the jack screws designed to remove the rotor basically stripped out and even a puller could not budge them. Those jack screws are worthless too IMO.