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View Full Version : 63 Avanti Rear Brake Drums - what gives?



dadondemand
09-23-2013, 08:21 PM
Just finishing up a complete rebuild of the rear brakes, including new wheel cylinders, grease seals and brake shoes, all from SI. Thought I'd slide the hubs and drums back on just to get them out of the way while I installed the new ss brake lines. However, the drums won't fit over the new brake shoes! Neither axle. And yes, the eccentrics are backed off all the way.

Anyone else ever had this problem? And more to the point - now what???

63t-cab
09-23-2013, 08:26 PM
Are the shoes against the cyls.?,maybe something wrong with the cyls.?

DEEPNHOCK
09-23-2013, 08:42 PM
Is there a lip on the edge of the drum?
Were the drums turned?
Are the linings oversized?
Are the wheel cylinders completely compressed?

dadondemand
09-23-2013, 09:00 PM
Is there a lip on the edge of the drum?
Were the drums turned?
Are the linings oversized?
Are the wheel cylinders completely compressed?

Drums were turned, but just a cleanup pass. No ridge on the turned surface that I can see. The replacement brake shoes came directly from SI - they don't show as having oversized linings in their catalog. Don't know if the cylinders are completely compressed, but the shoes are pushed together as far as the strut between them at the top of the backing plate will allow.

63t-cab
09-23-2013, 09:09 PM
I was trying to think how a lip could have anything to do with the drum not passing over the shoes ?
Is there a lip on the edge of the drum?
Were the drums turned?
Are the linings oversized?
Are the wheel cylinders completely compressed?

63 R2 Hawk
09-23-2013, 09:39 PM
I know there is a difference on rear shoes between the disc brake cars and the all-drum brake cars, I don't know if it's possible to install the drum style shoes on disc equipped cars, but might be something to look at. In the "old days", brake shoes were made oversized and then ground, or arced, to the exact diameter of the drum by grinding them to fit. Some places will still do that, but that process pretty much went away when it was discovered that asbestos dust was bad.

alaipairod
09-23-2013, 09:52 PM
Arching the shoes will solve your problem.............

Studebakercenteroforegon
09-23-2013, 09:56 PM
How about the emergency brake adjustment? You should back that off as needed also.

dadondemand
09-24-2013, 01:15 PM
How about the emergency brake adjustment? You should back that off as needed also.

Both emergency brake cables are presently disconnected, so they're not a factor in the positioning the brake shoes.

studegary
09-24-2013, 01:18 PM
How much are you missing by?
Arcing (not "arching") the shoes MAY help.

37CoupeE
09-24-2013, 01:21 PM
Have you tried comparing the new shoes to the old?
Try measuring the OD of the shoes and the ID of the drum.
Also are the shoes properly seated up and down and side to side.
Just some random thoughts.

StudeRich
09-24-2013, 01:59 PM
It would not be unusual to find some reliners using thicker lining assuming well worn and turned Drums as I have had those same type shoes not fit and had to be Arced to fit some very close to Standard Drums, you also could have your Machinist Mic the drums to see just how big they are.

You do know those are relined, as New is not available.

SN-60
09-24-2013, 06:53 PM
I know there is a difference on rear shoes between the disc brake cars and the all-drum brake cars, I don't know if it's possible to install the drum style shoes on disc equipped cars, but might be something to look at. In the "old days", brake shoes were made oversized and then ground, or arced, to the exact diameter of the drum by grinding them to fit. Some places will still do that, but that process pretty much went away when it was discovered that asbestos dust was bad.

Rear drum on disc equipped..11", rear drum on all drum equipped..10"

dadondemand
09-24-2013, 09:59 PM
How much are you missing by?
Arcing (not "arching") the shoes MAY help.

Hard to say, but it feels like I'm close. By arcing, do you mean "bending" the brake shoes to fit the arc of the drum?

dadondemand
09-24-2013, 10:02 PM
Have you tried comparing the new shoes to the old?
Try measuring the OD of the shoes and the ID of the drum.
Also are the shoes properly seated up and down and side to side.
Just some random thoughts.

I've tried moving the shoes around, in, out, up down, still won't clear. I don't have the original shoes to compare - turned them in to SI when I picked up the new ones.

brian6373
09-24-2013, 11:11 PM
I'm having the exact same problem! I have new shoes, wheel cylinders, and new finned brake drums for the 10" rears on my all drum brakes. The tops of the brake shoes are against the wedge, and the adjuster is all the way in. The parking brake cable is slack. I also insured that the shoes were centered. I compared the old shoes with the new ones and out of the four shoes they all looked to be about the same thickness as the new shoes, except for one that had about 50% of the lining worn down. The drums just won't go over the shoes! The drums and brake shoes are from S.I. I noticed that the drums were made in China, and we all know how the Q.C. from there can be somewhat lacking. I'm taking the drums down to the machine shop tomorrow and have them measured. If it turns out the drums are ok, I guess I'll take the belt sander to the shoes and "calibrate" them! I'll post more after I find out tomorrow about the brake drums.

Brian

37CoupeE
09-25-2013, 12:43 AM
Arcing the shoes is done on a machine that clamps onto the shoe and grinds the lining to the correct arch.
This is set by locating of the shoe to the grinding wheel.
Many shops had them in the past to properly fit shoes.
My dad picked up one years ago when a shop was tossing it out because of the worry of asbestos in the linings.
Still have it though, because it does come in handy sometimes.

Warren Webb
09-25-2013, 01:05 AM
I have seen the backing plates grooved too. Doesn't sound like your problem here but I would check anyway, just to be sure.

DEEPNHOCK
09-25-2013, 05:54 AM
Watch this video.
It gives you a real good idea of the brake shoe, wheel cylinder, and flywheel rebuilding/machining process..


http://www.youtube.com/watch?v=dIe9q95DscQ

brian6373
09-25-2013, 09:15 AM
Yes, the shoe platforms were badly grooved when I took off the backing plates. I ran a bead of weld and ground down the welds to restore the flat surface that the shoes ride on. Good thinking Warren! Too bad I'm not close to you 37coupeE, I could take my shoes over to you for a demonstration! Great video! I would kill for some of those machine tools! So, if the drums are good I need to reduce the shoe size. As we don't have any old school brakes shops around here that will arc brake shoes. What's a fella to do? Thanks for the help guys, Machine shop opens in about an hour, and I'll find out about the brake drum I.D.

Brian

brian6373
09-25-2013, 10:45 AM
Just got back from the machine shop. He measured the drums and they were .030 under 10". I told him to turn the drums so they were within specs. I'll get them back in an hour or so, and give them a try. I called the nice folks at S.I. and they offered to exchange the drums. Since both drums were the same undersize I figured that the ones in their warehouse are identical to the ones I already have with the same undersize problem. I didn't think that was a good solution. I counter-offered that they could reimburse me the cost of turning the drums to the 10" that they're supposed to be. They said they would have to talk to the owner first and get back to me. To be continued...

Brian

DEEPNHOCK
09-25-2013, 11:26 AM
Here's a 'Brakes 201' tip for you.
Try not to cut any more cast iron off of your drum than you have to.
The legal max cut is .060" by federal and state law.
(A 10" drum cannot be cut more than 10.060"..an 11" drum can be cut no more than 11.060"....)
You are best to just have your machine shop 'clean them up' and 'make them round'...
If he can do that with a .005" cut...great!
Oversized (thicker) linings are easy to sand down (with a shoe arc machine).
You can get a precise fit to the drum that way.
Hogging out a drum to fit an oversized lining is crazy, as drums are way harder (read that $$) to replace than a brake shoe is.
HTIH
Jeffhttp://forum.studebakerdriversclub.com/images/icons/icon6.png


Just got back from the machine shop. He measured the drums and they were .030 under 10". I told him to turn the drums so they were within specs. I'll get them back in an hour or so, and give them a try. I called the nice folks at S.I. and they offered to exchange the drums. Since both drums were the same undersize I figured that the ones in their warehouse are identical to the ones I already have with the same undersize problem. I didn't think that was a good solution. I counter-offered that they could reimburse me the cost of turning the drums to the 10" that they're supposed to be. They said they would have to talk to the owner first and get back to me. To be continued...

Brian

bezhawk
09-25-2013, 12:07 PM
You absolutely have the WRONG DRUMS!!!!! A DISC BRAKE REAR DRUM IS 11". I have several NOS in stock.

StudeRich
09-25-2013, 01:47 PM
Wow a Disc. Brake Avanti with a rear end swap from a DRUM BRAKE V8 Lark or Hawk, not a good fit for front Discs. :(

These would be the self energizing Bendix star wheel adjusted type, if that is so I would try reversing the Wedge at the top anchor to prevent that action. And then 11 inch rear Shoes for Front Discs will not fit a 10 inch Drum either.

But it still seems to me if you ordered New Avanti Rear Drums why would you have Lark Hawk 10 inch drums?
Something is not right here but without seeing the Backing plates I can't tell what is going on here. :confused:

Dwain G.
09-25-2013, 04:06 PM
The 10"drums belong to another poster that entered this thread.
On both cars, if the adjusters are backed off all the way and the equalizer bar (flat piece between the two shoes) has some slack to move back and forth a tiny bit, then yes, you are going to have to find someplace that will arc grind the shoes. Take the drums and shoes to a commercial clutch and brake shop.

StudeRich
09-25-2013, 04:49 PM
OK, thanks Dwain, I stand majorly CORRECTED!

bezhawk
09-25-2013, 06:50 PM
There is no equalizer bar, star wheel or anything like that on disk rears, the bottom is anchored they are not self energizing.

StudeRich
09-25-2013, 06:54 PM
bez, you and I have two different Cars mixed up from two different posters on the same topic!

See Post #25.

bezhawk
09-25-2013, 07:19 PM
bez, you and I have two different Cars mixed up from two different posters on the same topic!

See Post #25.Then somewhere the subject was changed. The original posting header mentions an Avanti

Dwain G.
09-25-2013, 08:53 PM
Disc or drum, they both have what I called an equalizer on the rear brakes. The parts book calls it a "Link, rear brake shoe operating".

bezhawk
09-25-2013, 09:25 PM
Dwain, are you talking about the parking brake link? http://www.studebaker-info.org/64v2488/Axle/ax7.jpg This is a rear drum set up for a Stude that has disk brakes.
Another tip....use stick on long board sanding paper 180 grit, and stick it to the inside of the drum. Rub your new linings around on it a little and it will arc the linings to conform to the contact area of the drum radius. Don't go too far.

brian6373
09-26-2013, 06:20 PM
Hi all! I'm sorry if I caused some confusion over the "who's got what" in this thread. The original poster is working on his 11" rear disc brake drums on an Avanti. I'm working on my 10" 63 cruiser brakes. It sounded to me like we both had similar problems. In conclusion of my problem; When I went to the machine shop, the machinist told me that both drums were .080" undersized. He took out material to make them exactly 10 ". They fit over the new shoes perfectly! problem solved. I got a call from a nice man ( I don't remember his name) from S.I. I had measured the linings as they had requested to make sure I didn't have HD shoes by mistake. He also told me that he's going to check the runout on their other drums they have in stock to make sure that they don't have other ones with such a gross undersize. He agreed that it was reasonable to pay for the drum turning. Thanks again for all the helpful info and again I apologize for any confusion that I caused.

Brian

DEEPNHOCK
09-26-2013, 07:55 PM
Not nitpicking Brian, but that makes no sense.
A 10" drum is not made .080" smaller than 10".
It is easy to measure a 10" drum (a bunch of companies make drum measuring devices if a ruler won't work)...
The max you can cut a 10" drum is to go to 10.060"....by law.

If your machinist cut your drum an extra .080" to match the drum to the shoe... He just broke the law.

Runout has to do with the drum being indexed on the hub (or the brake drum lathe).
I can tell you... If you had .020" runout on a drum, your teeth would chatter every time you stepped on the brake.

An 'automotive' machinist will be familiar with the conditions you describe.
A 'machinist' might not have a clue, except width, depth, and height.

Any good auto shop should be able to check your drums and advise you as to your 'proper' course of action.

And the S.I. guy should know better than to tell you a HD lining will fit differently than a std lining.
The 'HD' in brake lining has to do with the material in the friction block.... NOT the size of the block.
If they are selling 'oversized lining', it had better not be more that .060" (diameter) larger than stock, or they are selling lining to fit an illegally oversized drum...and I doubt they would do that.

This is NOT rocket science. It is automotive drum brakes 101, and it has been around for 100 years.
Only the materials have changed. Not the sizes.

Let's keep our forum info straight....and accurate.
People's lives are at stake.....not to mention our precious Studebaker's.......
HTIH
Jeffhttp://forum.studebakerdriversclub.com/images/icons/icon6.png


<snip>
I'm working on my 10" 63 cruiser brakes. It sounded to me like we both had similar problems. In conclusion of my problem; When I went to the machine shop, the machinist told me that both drums were .080" undersized. He took out material to make them exactly 10 ". They fit over the new shoes perfectly! problem solved. <snip>
Brian

37CoupeE
09-26-2013, 11:50 PM
If the machinist measured the drums and they were .080 undersize he cut them to 10", which is what they are supposed to be.
If these drums were left over factory stock they could have been undersize and that is why they had them.
If they are new, where were they made? If they are imported - there's your answer.
Most items coming into this country are not inspected, I see this every day on sizes on imported parts.
I see no harm no foul taking them to the correct size of 10.000"

brian6373
09-27-2013, 12:54 AM
What 37CoupeE said. In my post # 16 on this thread I said the drums were manufactured in China. I took the drums to my local NAPA auto store that has a machine shop. I would assume that the machinist there was an automotive machinist. When he measured the drums with a brake drum micrometer the drum was 9.920". After turning the drum it was 10.000". No laws were broken in the turning of these drums. I should be able to get another .060" out of the drum before it is condemnable. Not having any history of the manufacturer in China I don't know why they allowed undersized drums to be shipped to S.I. in that condition. I just know that it was when I received them. After bringing the turned drums home I compared them to the old drums. The new drums still had about twice as much turnable surface on them. Yes Jeff, I misspoke myself about "runnout". I do understand that that term is used to define the amount of non-concentricity. As a side note, I did go to College as an automotive major 35 years ago. Since then I have worked on many different brake systems in the transportation industry. If you have advice I will always be willing to listen. Just try to keep the condescending tone out of it. No hard feelings huh?

Brian

37CoupeE
09-27-2013, 01:12 AM
Brian,

I'm glad you got them to fit.
Hope you enjoy driving your car with good brakes now.
As they say Size matters.

DEEPNHOCK
09-27-2013, 07:36 AM
No hard feelings on my end...
But why did it take a contrarian reply to draw the rest of the info out from you?
A forum post, especially a technical post, and double especially when questions are asked in a post... It should have all the pertinent info laid out.
Hard to diagnose a 'It doesn't fit', when all the variables aren't presented.
But... That's what is good about this forum.
We can talk about things.

I get very concerned when misleading, vague, or incorrect information gets posted on a forum.
Somebody could read it wrong, and go out and make a horrendously wrong decision.
Not saying that happened here, but the casual reader might not be aware of legal regulations.

I also would not be so fast to condemn all offshore products.
Some of their Q/C and manufacturing equipment is light years ahead of the old stuff in the USA.
But it takes a sleuth to find that out.
Look close where almost all of the cast iron products are coming from these days.
It is an eye opener.

I stand by what I wrote. Wasn't trying to be condescending... Just trying to be accurate on a tech post.
I would find it hard to believe that SI would be selling undersized drums.
Every customer would have the same issues you are having (which is possible, I suppose).
What did they say about this?
Jeffhttp://forum.studebakerdriversclub.com/images/icons/icon6.png


What 37CoupeE said. In my post # 16 on this thread I said the drums were manufactured in China. I took the drums to my local NAPA auto store that has a machine shop. I would assume that the machinist there was an automotive machinist. When he measured the drums with a brake drum micrometer the drum was 9.920". After turning the drum it was 10.000". No laws were broken in the turning of these drums. I should be able to get another .060" out of the drum before it is condemnable. Not having any history of the manufacturer in China I don't know why they allowed undersized drums to be shipped to S.I. in that condition. I just know that it was when I received them. After bringing the turned drums home I compared them to the old drums. The new drums still had about twice as much turnable surface on them. Yes Jeff, I misspoke myself about "runnout". I do understand that that term is used to define the amount of non-concentricity. As a side note, I did go to College as an automotive major 35 years ago. Since then I have worked on many different brake systems in the transportation industry. If you have advice I will always be willing to listen. Just try to keep the condescending tone out of it. No hard feelings huh?

Brian

brian6373
10-03-2013, 09:44 AM
Good morning all! I just got off the phone with Ed from S.I. They checked their inventory on the 10" brake drums and they were all undersized! They're sending them out to be turned before they sell them. He was telling me about having door hinge screws that they had reproduced, the samples looked good, but when the order came in they wouldn't fit. 10,000 bad screws. Just goes to show that even new parts can be bad.

Brian