Measuring brake hubs.

[moparkrazed]

Hey guys, I’ve got a 66 valiant and I need new drums for them. It’s drums all the way around with a 170 slant six. I’m sure I have 9 inch drums but want to be safe. I’ve taken measurements but not sure if I go inside to inside or outside to outside on the drum. I’ve attached pics for verification.

 

[RandyB]

9”

 

[Murray]

Proper way is to measure the inside diameter. You have a 9" diameter drum. Professionals have a more accurate gauge that measures down to .001 to determine how much the drum has already been turned. They have limits.

 

[TAK65]

Would be also interesting which brand of drums would be dependable. When I ordered new drums for my 64 Valiant a few years ago, the mechanic ended up having the originals turned after all. Told me the new (Chinese?) ones were so out-of-round he thought the original ones would be safer to use.

 

[Murray]

Todays mechanics are mostly just parts replacers. In the old days it was standard procedure to always turn new drums "just in case". When you turn a drum you can choose to cut "little" or "much". Taking a "little" to true it up may be under .010. For the best job, I recommend turning. Just chucking up the drum before turning, you can see if it's out-of-round.

 

[moparkrazed]

Todays mechanics are mostly just parts replacers. In the old days it was standard procedure to always turn new drums "just in case". When you turn a drum you can choose to cut "little" or "much". Taking a "little" to true it up may be under .010. For the best job, I recommend turning. Just chucking up the drum before turning, you can see if it's out-of-round.

Thanks for all the answers guys. I figured they were 9 inch drums but no need to guess when I can ask. These are original drums as far as I know but there is a nice line ground into them. I’ll have them checked to see if they can be turned. Thanks again y’all.

 

[67Dart273]

Drum systems are deceivingly complicated. Drums can wear bell shaped, "humped" in the middle, with all kinds of variations. Plus they wear with a ridge on the inner and outer edges which interfere with new shoes. In other words, new shoes won't fit well into the oddly worn drum

So you turn it what then?

If you turn a drum "much" the drum of course becomes larger and so the shoe now rocks in there with only the center area of the lining touching, and this does two bad things: First less shoe lining is touching the drum, so there is effectively less braking force/ shoe area. Second, because the middle/ center area of the shoe is doing the work, that part gets hotter and GLAZES, which then makes it LESS effective, and now you have very very poor brakes. You can push on the nice hard pedal until you break something and IT JUST WON'T STOP

So you have to have the shoes matched to the drum which is called "arcing" the shoes on a special machine---which I bet not 1 shop in a hundred has anymore. ****, nobody has drum/ disc lathes anymore, either.

 

[Projectile Dart]

To the O.P. just as a general rule of thumb, I have yet to find a set of drums that did not have some sort of wording on it to indicate the rough size they are supposed to be (9", 10", 11" etc.) along with a note of what the safe cutting amount is
These letters are likely going to be covered in rust/general crud but a quick pass with a wire brush will make them pop

 

[moparkrazed]

Drum systems are deceivingly complicated. Drums can wear bell shaped, "humped" in the middle, with all kinds of variations. Plus they wear with a ridge on the inner and outer edges which interfere with new shoes. In other words, new shoes won't fit well into the oddly worn drum

So you turn it what then?

If you turn a drum "much" the drum of course becomes larger and so the shoe now rocks in there with only the center area of the lining touching, and this does two bad things: First less shoe lining is touching the drum, so there is effectively less braking force/ shoe area. Second, because the middle/ center area of the shoe is doing the work, that part gets hotter and GLAZES, which then makes it LESS effective, and now you have very very poor brakes. You can push on the nice hard pedal until you break something and IT JUST WON'T STOP

So you have to have the shoes matched to the drum which is called "arcing" the shoes on a special machine---which I bet not 1 shop in a hundred has anymore. ****, nobody has drum/ disc lathes anymore, either.

Thanks for the list 67dart. That actually makes a lot of sense the way you explained that. I can almost guarantee no one around me has those tools anymore. I’m surprised when someone knows show to align the front end these days haha.

 

[moparkrazed]

To the O.P. just as a general rule of thumb, I have yet to find a set of drums that did not have some sort of wording on it to indicate the rough size they are supposed to be (9", 10", 11" etc.) along with a note of what the safe cutting amount is
These letters are likely going to be covered in rust/general crud but a quick pass with a wire brush will make them pop

Thanks projectile. I’ll take a closer look. When I pulled the tire off during lunch it was looked like a spider at some point built a mansion on the drum. I’ll hit it with a wire wheel. I’m pretty sure the are 9 inch but doesn’t hurt to clean things up anyways. I’m not even close to doing the brakes yet but coming up with a plan and parts list and a budget to blow past right now haha.

 

[Scody21]

Most parts stores can turn drums and rotors. Last set I had done was 25 bucks

Also check rock auto. Seeing new drums from about 17 bucks and up... not saying there great, but an option...

 

[moparkrazed]

Most parts stores can turn drums and rotors. Last set I had done was 25 bucks

Also check rock auto. Seeing new drums from about 17 bucks and up... not saying there great, but an option...

Yeah I’ll check to see what it would to have them turned at least. The groove in the drum feels pretty deep so it may be beyond saving. Thanks for the heads up on the parts