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63 Avanti Rear Brake Drums - what gives?

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  • brian6373
    replied
    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

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  • DEEPNHOCK
    replied
    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?
    Jeff


    Originally posted by brian6373 View Post
    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

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  • 37CoupeE
    replied
    Brian,

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

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  • brian6373
    replied
    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

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  • 37CoupeE
    replied
    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"

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  • DEEPNHOCK
    replied
    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
    Jeff


    Originally posted by brian6373 View Post
    <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
    Last edited by DEEPNHOCK; 09-26-2013, 05:58 PM.

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  • brian6373
    replied
    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

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  • bezhawk
    replied
    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.
    Last edited by bezhawk; 09-25-2013, 08:09 PM.

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  • Dwain G.
    replied
    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".

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  • bezhawk
    replied
    Originally posted by StudeRich View Post
    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

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  • StudeRich
    replied
    bez, you and I have two different Cars mixed up from two different posters on the same topic!

    See Post #25.

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  • bezhawk
    replied
    There is no equalizer bar, star wheel or anything like that on disk rears, the bottom is anchored they are not self energizing.

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  • StudeRich
    replied
    OK, thanks Dwain, I stand majorly CORRECTED!

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  • Dwain G.
    replied
    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.

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  • StudeRich
    replied
    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.

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