Brake drum clearance

-
dibbons

dibbons

Well-Known Member
Joined
Nov 6, 2009
Messages
5,722
Reaction score
3,785
Location
La Paz, B.C.S., Mexico
I am working on a 65 Formula S, factory power drum brakes.

First off, let me ask if it is alright to jack up the front end with a floor jack placed in front of the oil pan on the crossmember (is that called a "K member"). Well, that is how I did it and then placed jack stands behind the rear tires/inside the doors on what looks to be the frame of the vehicle. OK so far?

The brakes were all renewed some years ago, but the vehicle has only been driven 2,000 - 3,000 miles since then (maybe even less).

Now when I spin the front tires while they are suspended mid-air, I here rubbing/grinding inside the drums.

On the passenger side, it is not constant, only each time a certain wheel stud is at the 12 o'clock position. The tire/wheel will still free wheel/free spin a few times befor coming to a stop.

On the driver's side I hear the same sound, but it is more constant during the entire spin of the tire/wheel and it is difficult to get a full spin before it "grinds" to a stop.

If I remember correctly, there were self adjusters on the front brakes. (Someone swapped in an 8 3/4 differential with a 489 case, and those rear drum brakes I know have manual adjusters).

Should I be concerned with the condition of the front brakes? Is one side or the other causing a safety issue? Thank you.

DSC01276.JPG
 
It could just be a little rust or something between the edge of the drum and the backing plate.
If you're really curious you'll have to take the drum off to look for contact marks.

Some good tips on brake service in the master tech series.
Master Technician Service Conference - Chrysler's Training for Mechanics
Scroll down to '60s.

Just be careful when looking the ones from '69 up. In 1969 adjuster hardware and shoes changed. So those won't look the same and (work in the opposite direction).
 
It is rare that drums turn freely, REALLY freely, or do so without scraping "some." If the drums are out of round, this would explain scraping "in one spot." The fact that (you said spin) at least one/two/ ?? tires "spin" indicates they are "free enough." What do you have in the way of pedal above the floor, and is this power or manual brakes?
 
Driver's side drags pretty bad, I would not say it spins at all freely. The power brake pedal is pretty low, but I was reading somewhere it was designed that way (at least in '65) to better match up to the accelerator pedal.
 
Is the engine running? if so you can over ride the booster by pushing to hard. You really need to drive it and see how far the pedal goes down to stop the car. If one wheel is way out of adjustment it can give you a low pedal. If all are out of adjustment it can put the pedal almost on the floor.
 
The motor is rebuilt, runs fine. I had "low pedal" until we adjusted the rear drums, which like I mentioned above, have manual adjusters. The pedal height is no longer an issue.
 
dibbons said:
Driver's side drags pretty bad, I would not say it spins at all freely. The power brake pedal is pretty low, but I was reading somewhere it was designed that way (at least in '65) to better match up to the accelerator pedal.
Click to expand...

No I mean "when they are applied" trying to get some idea of where you are on adjustment
 
I'll measure tomorrow with a tape measure how far off the floor the brake pedal is when applied at a standstill.
 
No need, what is "your feel?" Does the pedal feel "normal range" or a "lot too close to the floor?" Again, just trying to get a feel for where the shoe adjustments is.
 
I was reading about rust issues causing problems between drum and backing plate, that is a new one on me (always thought noises originated from drum/show problems. Anyway, that is something else to think about in this case.
 
dibbons said:
I am working on a 65 Formula S, factory power drum brakes.

First off, let me ask if it is alright to jack up the front end with a floor jack placed in front of the oil pan on the crossmember (is that called a "K member"). Well, that is how I did it and then placed jack stands behind the rear tires/inside the doors on what looks to be the frame of the vehicle. OK so far?

The brakes were all renewed some years ago, but the vehicle has only been driven 2,000 - 3,000 miles since then (maybe even less).

Now when I spin the front tires while they are suspended mid-air, I here rubbing/grinding inside the drums.

On the passenger side, it is not constant, only each time a certain wheel stud is at the 12 o'clock position. The tire/wheel will still free wheel/free spin a few times befor coming to a stop.

On the driver's side I hear the same sound, but it is more constant during the entire spin of the tire/wheel and it is difficult to get a full spin before it "grinds" to a stop.

If I remember correctly, there were self adjusters on the front brakes. (Someone swapped in an 8 3/4 differential with a 489 case, and those rear drum brakes I know have manual adjusters).

Should I be concerned with the condition of the front brakes? Is one side or the other causing a safety issue? Thank you.

View attachment 1715106461
Click to expand...
Always chock the rear wheels when jacking up the front end and vise versa when jacking up the rear end.
 
dibbons said:
I was reading about rust issues causing problems between drum and backing plate, that is a new one on me (always thought noises originated from drum/show problems. Anyway, that is something else to think about in this case.
Click to expand...
The shoes ride on little pads on the backing plates. If those contact areas are not lubed they can cause hanging issues of the shoes causing noise. Those little pads need some lube. A dab of silicone "Stay Put" is my suggestion for those areas.
 
Took off the driver's side drum, was pretty clean inside, not really rusty, not dusty, not blue (from heat), not scored. And the bonded linings were as thick as new. So I backed off the star adjuster some and that seemed to free up the drum to spin a little. Rotating, it still rubs when it comes around to a certain spot. It sounds like it is scraping a little in the area of the rear brake shoe (it sounds the same as the passenger side now, but the passenger side is just barely grazing the same spot).

It appears perhaps the drum is a little out of round. Not only that, but I seem to remember a local brake shop manually adjusting the brakes some time ago. It may have been they got the drivers side a little tight.

So I put it back together as is, tightened the spindle nut (hand tight only) and then the castle nut thing and new cotter pin. Decided to de-grease, apply Ophso, and then paint the drums (they will show through the rallye wheels so why not?) before I slap the tires back on.

During the next road test, I will see if it brakes straight or pulls to one side or the other.
 
That sounds like the drum is a bit out of round and really hate to even mention this BUT back when most shops had a machine to grind the shoes to the same arc or dia of the drum, old school doubt you will ever find a place with one of those now.
2lbceio.jpg
 
That "arc" grinder looks familiar, I used that back in our high school auto shop class (circa '72-'73). For sure that is a good idea, and for sure my brake shoes did not receive that same fine tuning they could have had if such grinder was available. But I will keep my eyes open to find one in a local shop or for sale somewhere (flea market?).
 
Would not be cheap for just that use, we used to match the shoes to the cut drum diam. We used this one.
Wonder if they are still legal? Prob need a hazmat suit to use one now.
 
Drive it around hit the brakes stop, backup hit the brakes, go forward for a while hit the brakes stop, back up hit the brakes, go forward a block hit the brakes, back up hit the brakes then see if you still have the same drags when you jack it up again.
 
halifaxhops said:
Wonder if they are still legal? Prob need a hazmat suit to use one now.
Click to expand...
Great pics!
Porterfield will arc their linings. I gave 'em the diameter my drums. The drums I had lightly cut at East Coast Machine.
Another lining place that will arc them is Rochester Brake and Clutch. Locally, I think you just got to sniff around. A local parts store (now closed) was using Pennsylvania Brake for relined shoes and pads - they were right in the City - also closed now. :(
 
You must log in or register to reply here.
-

Back
Top