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my 63 has two brake drums with external springs around drum and two without.can anyone tell me if original drums had these springs and what is there purpose, cooling or chatter?
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Re: brake drum springs (external)
Both of the front drums on my '64 had these. I know they are the originals- but I can do no better than a guess as to why they were there. I know somebody on the board can tell you what they are for, as well as the part number original finish, carbon content of the original steel, and the name of the guy who made them while working third shift in 1963. In case you haven't noticed, I am in awe of the people who memorize this stuff and spend time answering our questions. -
Re: brake drum springs (external)
The drum springs seem to be hit or miss proposition. They are there to damp brake squeak, which is caused by high frequency drum vibration. I was missing at least one on my original SWC J65 drums. (As a side note I believe the J65 metallic brake option to the standard sized brake package had a finer surface finish on the drum friction surface, which is why the replacement drums had a different p/n that the base drums) It's possible that they were only installed on one end. Can anyone else comment on this? In any event, one or two more arrived with the replacement J-65 drums in the seventies, so I now have a spring on all four. The drums are cast iron not steel, and I haven't yet figured out who made them, but I'm still working on it.:-)
DukeComment
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Re: brake drum springs (external)
Duke----
As far as the brake drum spring goes, for NON J-56/J-65 equipped cars the spring was GM #3694290. This is a spring of 32.75" free length and, believe it or not, at least as of the end of last year, it was still available from GM for a list price of $10.50.
For J-56/J-65 equipped cars either a) no spring was/is available as a seperate service part, or b) no spring was originally used.
As far as the drake drums go, virtually all brake drums were manufactured from gray, ductile, or nodular iron. Most, if not all, GM-manufactured drums were cast at the old GM Danville, IL foundry and machined/finished at the Delco brake plants in Dayton, OH. Check for the "wagon wheel" casting symbol somewhere on the drum and/or a "D" casting mark. The "wagon wheel" will confirm that the part was cast in a GM Central Foundry Division plant and a "D" will confirm that that plant was the Danville, IL foundry. Unfortunately, not all castings are so-identified even if they were produced at Central Foundry Division and the Danville or other foundry.In Appreciation of John HinckleyComment
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Re: C1 brake drum springs (external) too?
Is that part number you gave for the C2 brake springs common to the C1 cars too?Comment
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Re: brake drum springs (external)
My late 64 has the original drums and springs on front drums only.If my memory is correct,according to noland adams book cars with metallic lining J-60 had different part numbers for the drums .Comment
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Re: C1 brake drum springs (external) too?
Doug-----
Yes. All 53-62 C1s except those with HD brakes.In Appreciation of John HinckleyComment
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Re: brake drum springs (external)
Jim-----
That's correct. Non metallic brake 63-64 Corvettes used drums GM #3830166-front and GM #3868801-rear. Metallic brake 63-64 Corvettes used drums GM #3872384-front and GM #3869537-rear. There may also have been other predecessor and successor part numbers.In Appreciation of John HinckleyComment
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This might be a long one (brake springs)
There's a lot of conflicting information here. First, the J65 (RPO 686 from '59 to '62) option was basically an upgrade of the base system to sintered metallic linings and was availble in '63 and '64. This was a low cost option, $37.70 from '60 and '64, and $26.90 on '59s. RPO J56 ($629.50)was a '64 option that consisted of the '63 Z06 brakes, broken out to a separated option. So let's not get into the Z06/J56 brakes for now as this was a totally different system from the master cylinder to the wheel hardware.
My '77 vintage parts manual calls out the 3694920 spring in group 5.810 for the drums as follows:
53-62 Y(EXC. H.D. BRAKE/SUSP.)
63-67 Y(EXC. SP.H/PER.)..........3994920 A.R. (Spring, 32 3/4" FREE LENGTH)
It's notworthy that the quantity listed is "as required". Also, listing the applicability through '67 is obviously suspicious. The implication here is that they apply to all four wheels. Both the front and rear drums are listed in group 5. It's always been my understanding and belief that the J65 drums are the same casting as the base drums, but have a finer surface finish on the friction surface, and this is supported by a note on page 5-16 of the '63 shop manual that says: "BRAKE SHOES WITH METALLIC LININGS REQUIRE SPECIALLY FINISHED BRAKE DRUMS (HONED TO A 20 MICRO-INCH FINISH). METALLIC FACINGS ARE NOT RECOMMENDED FOR SERVICE REPLACEMENT ON VEHICLES WITH STANDARD BRAKE DRUMS THAT HAVE NOT BEEN HONED TO THE SPECIFIED FINISH."
The text in this section indicates that it applies to both the J65 and Z06 brakes (J56 in '64). Another note states: "SPECIAL HEAT RESISTANT BRAKE SPRINGS ARE REQUIRED FOR METALLIC BRAKES". While I do more research, let's hear from others. I'd like to get to the bottom of both the drum spring issue and the differences between the base brakes and RPO 686/J65.
DukeComment
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Re: This might be a long one (brake springs)
Duke -- My interpretation (at least on C2's) is much the same as yours; the '63/64 J65 brakes could have had springs. Whether they are formed from the round wire or flat is another point. A '63 I used to own, (# 7055), had J65, and the front drums definitely had the anit-squeal springs around the outside circumference of the drum. I'd have to check my photos to say if the rears had them, and whether they were round or flat wire. Also, the (internal) pull-back springs were color-coded differently from regular brake springs.
My '70 Corvette Parts Manual also checks out the same as yours for the spring #, length and applicability. Another clue that the drums for the metallic linings and regular brake might have been from the same casting, is both fronts differ by only one part # (3830166 and 3830167, respectively).
The Z06/J56 drums could not have springs because of the fins.Comment
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Re: This might be a long one (brake springs)
Duke-----
I really question whether there is "a lot" of conflicting information here. First off, I think that it's quite clear that the 3694920 spring was used on 53-62 Corvettes and "some" 63-64 Corvettes, excepting "sp h/per". What is meant by "sp h/per" is open to question. It definitely includes J-56(because as Wayne M mentioned the J-56 brakes couldn't use springs due to the fins) and it MAY mean J-65. I guess I would have to revise the 2 possible alternatives which I presented in my original post to be 3 possible alternatives a) the J-65 brakes used a brake drum spring which was never available as a seperate service part; b) the J-65 brakes used no drum spring OR c)the J-65 brakes used the same brake drum spring as non-J-65 drums(i.e. the 3694920).
With respect to whether the 63-64 cars with any brake system used drum springs on just the front drums, just the rear drums, or both, I have no idea. That's why I didn't comment on that point in my original post. My general observation has always been that these springs are usually just seen on the fronts, but I'm really not sure for 63-64 Corvette applications. The "as required" notation in the parts manual does not really have any particular import or provide any hint whatsoever with respect to how many were originally installed on the car. When GM uses this notation in the "number required" column of the parts manual, it usually means that the number required varies with the specific application OR it means that this is a service item with an indeterminate number needed depending upon "how many you currently have which are unserviceable". Either or both could have been their intention in this case.
Also, the 63-67 model year applicability in this case is not so surprising to me. Obviously, no 1966 or 67 Corvettes had drum brakes requiring the drum springs(although a few 65s did). However, the drum springs were also used on many other cars post-1965 and sometimes "vestiges" of this applicability will "creep over" into Corvette-only parts manuals. I regard these instances as anachronisms and find them from time-to-time in various parts groups, particularly with respect to "common-usage" type parts.
As far as the notation in the service manual which refers to the need for special springs for cars with metallic brakes, I believe that notation refers to the brake shoe springs, NOT the drum springs. The drum springs have no safety or performance implication whatsoever and I doubt that any compromise in the integrity of these springs would warrant such a warning in the service manual. As a matter of fact, 63-64 Corvettes with "standard" brakes used one set of brake shoe springs, those with metallic(J-65) brakes used another set, and those with HD(J-56) used still another.So, that fact would tend to support the theory that the notation which you referred to related to the brake shoe springs.In Appreciation of John HinckleyComment
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Good summary
I believe the "EXC. SP.H/PER." qualifier for the C2 brake drum anti-squeak spring refers to the Z06/J56 package. That leaves the "base" and J65 brake option. Based on my own original J65 drums, which were equipped with a less than complete set of drum springs, likewise with the service replacements, I believe that your alternative "c" is the answer, but the evidence is not conclusive. Ian did not report which drums had springs. Both Shane and Jim report front only. None indicated whether their cars were base or J-65, and at this point it may be difficult to tell whether or not a specific car was originally equipped with J-65 unless the owner possesses some original documentation. Replacement of parts over the years could eliminate any evidence of the original configuration.
My current belief is that J-65 drums were the same as base drums except for the surface finish, so a different spring for J-65 drums doesn't seem likely and the parts book supports this. As a courtesy to Ian who started this thread I should probably limit the discussion to the drum anti-squeak spring issue, but I plan on starting a thread on the 686/J65 metallic brake option as soon as I do a bit more research.
I agree that the note in the '63 shop manual refers to some or all of the internal springs, not the drum anti-squeak spring. One other observation from the '63 shop manual: Of the two clear pictures of a (base) brake drum, one front and one rear, neither have an anti-squeak springs.
DukeComment
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