So I went to have my rear drums turned today. The shop manual says that the diameter should be between 11.995" and 12.005". My question is since the sidewall is ridiculously thick compared to the specified tolerance, would turning them outside the max diameter say .2" really matter? The machine shop mic'd mine and found they were already at 12.005" and still need to be turned since they're grooved.
Turning brake drums
- Thread starter Loren Baldwin
- Start date
You are flirting with disaster! The pistons in the wheel cylinders have a sweet spot in the parameters they are designed to work in, within the wheel cylinders. Brakes are designed and specs created for a purpose. THE MOST IMPORTANT PART OF AN AUTOMOBILE ARE THE BRAKES. Safety first, always, please remember that your entire life. Always use jackstands that are rated for the weight for example. Please use the common sense that is not to common any longer. Not to long ago we drove up on an accident scene where an old heavy military style OD trailer come off the trailer hitch of a truck and run away onto a side walk and kill a mother and her child both were riding bikes on the side walk, and got runned down from behind with no chance to save themselves. You could not live with your conscience if you had caused such an accident.
grove don't hurt it none. don't worry about it just light trim to check the taper in it. the groves give you more stopping power. if your at max don't go over to take out a grove. you will loose the stopping power if you do. you go over and all that touches is the vary center of the brake shoe.
I second what John-Ed says above, grooves aren't nearly as harmful as going over. There are two reasons not to exceed the max diameter. The first, of course, is cooling/heat dissipation. The second is that the arc of the shoe and lining has to match the arc of the drum, so as to have maximum area of contact. You should "fit" the shoe by hand to the drum, prior to installing the shoes to visually check that the full surface of the shoe contacts the drum. What you do not want is a rocking, or teeter-totter effect.
Before the dangers of asbestos became well known, most shops or parts houses could "re-arc" shoes and fit them to the drums. These days, your best bet to find someone who still re-arcs shoes locally to you would be a restoration shop that specializes in 1950's or earlier cars, or a farm implement repair shop. I am pretty sure that White Post does it, but you'd have to send off shoes & drums to them, so $hipping would be right $$$pendy.....
Before the dangers of asbestos became well known, most shops or parts houses could "re-arc" shoes and fit them to the drums. These days, your best bet to find someone who still re-arcs shoes locally to you would be a restoration shop that specializes in 1950's or earlier cars, or a farm implement repair shop. I am pretty sure that White Post does it, but you'd have to send off shoes & drums to them, so $hipping would be right $$$pendy.....
Darren Bedford
PCS Member
THE MOST IMPORTANT PART OF AN AUTOMOBILE ARE THE BRAKES.
Well said Michael !
Doesn't matter how fast you can go...
It's how fast you can stop !
I would look for another set.
Can anyone point Loren in the right direction ? Part numbers ?
You can use those until you get the car ready for the road but brakes are something you don't want to mess with.
I had a rubber brake line go before and luckily I prevented a disaster/crash with a quick reaction but no brakes at all. A few minutes later it won't have been possible.
Speaking from experience... and one I wouldn't ever want to have again !
Darren
Well said Michael !
Doesn't matter how fast you can go...
It's how fast you can stop !
I would look for another set.
Can anyone point Loren in the right direction ? Part numbers ?
You can use those until you get the car ready for the road but brakes are something you don't want to mess with.
I had a rubber brake line go before and luckily I prevented a disaster/crash with a quick reaction but no brakes at all. A few minutes later it won't have been possible.
Speaking from experience... and one I wouldn't ever want to have again !
Darren
Danny Ryder - Deceased - 1962 - 2021
PCS Life Member
It is getting harder to do but key here is find someone who can still work on these old cars we so enjoy. After my mechanic of 30 yrs retired I started having trouble with my 70 hearse with stopping as one front brake would grab before the other. Took several places and ask lots of folks what to ck and I figured one of the calipers was sticking but replacing those did nothing to help. Couple years later of putting up with this we had a guy start doing repair work at the car lot and I ask him about it and told him all my efforts. He jacked it up and looked it over and checked a few things and said I needed the rubber brake line on one front wheel. He said after 40 yrs it had partially collapsed inside and restricted flow of brake fluid. A $20 hose and it was cured. 
The Cadillac parts book give some information. The 1956 through 1959 Cadillac commercial chassis use the same brake drums. Starting in 1960, there is a new number for the rear commercial chassis drums, and there is a separate part number for the Miller Meteor commercial chassis. They refer to a brake cylinder casting number to differentiate between the 2 1960 commercial chassis parts. Then starting in 1961 through 1965, they are all the same. Unfortunately, this is a 1968 printing of the parts book, and it doesn't give all the information that some of the older books give. I think that your best bet is to search for some used drums.
If it were mine, I would rebuild the entire braking system, and use over sized riveted linings and just hand sand the drums that are on the car. You are not going to be drag racing this car, so if you fix the hydraulics to be like new, and install new over sized linings, the car is going to stop as well as it did in 1959. I don't believe in chasing a groove in a brake drum, since you don't have enough material to cut the groove out.
If it were mine, I would rebuild the entire braking system, and use over sized riveted linings and just hand sand the drums that are on the car. You are not going to be drag racing this car, so if you fix the hydraulics to be like new, and install new over sized linings, the car is going to stop as well as it did in 1959. I don't believe in chasing a groove in a brake drum, since you don't have enough material to cut the groove out.
In my 1969 cad sovereign, I had the center of my original drum separate from the outer section. Even more interesting is that axle broke later that year. Now are the drums and wheel cyclinders the same as the Fleetwood 75? I know the wheel cylinders have different bores, and I can only find two.
Your worst enemy is the quick lube places, and places that advertise or specialize in fast brake jobs. They hire young monkeys, and try to make an extra buck on your ride.
If you cant do it yourself, take it to a shop that is full of SAE auto mechanics. You just cant beat experience.
If you cant do it yourself, take it to a shop that is full of SAE auto mechanics. You just cant beat experience.
most likely the axle was bent causing a out of balance problem. the flexing broke the drum and finally the metal fatigue took out the axle.
the book says that it has to be a 1969 commercial chassis. 1968 is different 1970 is different as is the 75 series in those years. gm axle part number 3514681 is the right side number and 3514680 is the left one. right and left are different shafts. as the right one is longer
I figured thats what it was. I ended up putting in the G1 "controlled differential" and custom axles. My engine will appreciate that, my tires may not. I was more curious about the brake parts for 69. I dont know if the drums and wheel cylinders for fleetwoods and 75's are the same fitment for CC cars. All the manufacturers sell one type of rear drum and two sizes of wheel cylinders, which look different than my shot originals. Even with the same bore.