65 - disk & drum combi

[Michael H.]

Re: 65 - disk & drum combi

Hi Bill,

This is a really interesting question. I think I've only seen a few of these drum brake 65's in my life and I never thought to inspect the configuration of the rear control arm.

I really don't know the answer but I would have to believe the frame was the standard 65 unit with the depressions in the side rail for caliper clearance and the upstop bumper pad in the conventional 65 position. I wouldn't think that there would be a different part when the production 65 would work for the drum installation.

The upstop bumper location on the control arm of a disc brake unit would require the frame mounted pad to be inboard of the 63-64 location so I have to wonder if 65 control arms were used but built up with the drum brake setup instead of the disc. I don't even know if that's possible but it would solve the problem if it were. Only thing that would require mod would be the addition of the drum brake style parking brake cable bracket.

The entire rear control arm and brake assembly would have to have been a part/number unique to this option.

The addition of the parking brake cable bracket would have given this particular control arm a unique part number that was likely never available in service.

It would also be possible to use a complete 64 style drum brake control arm assembly if the later style 65 upstop bumper pad were added.

[Eric J.]

What Noland's book says....

Michael, On Page 273 Noland's R & T Guide Vol 2. Noland sites another possible 'hybrid', Noland states that #21,155 had rear drums only. Although he does not confirm that this was "factory" he does pose the possiblity that it may be. Now that we have another possible hybrid #23,197 I would work to document your car's part numbers dates etc.. on the swing arms spindles etc. You may have a very rare car.Eric 3,182

[Drew P.]

Re: 65 - disk & drum combi

Hello Michael,
I was hoping to see a photo if the brake master cylinder. This will answer the question of what configuration.
Regards,
Drew Papsun

[Bill Stephenson]

Re: Taking that a little further:

------Early 65 frames didnt have the indentation for a big-block balancer anyway, nor the sidepipe slots. If the car in queastion has the indent I would bet that the drum-brakes have been switched onto the rear for some odd reason.......Bill S

[Michael W.]

Re: Taking that a little further:

Drew - I have a single master cilinder.

All - i checked my frame and there is no indent on both sides. Also my car was no side-pipe car since I have an AOS body and there were never supplied with that option as I have always understood.

Michael

[Michael W.]

Re: 65 - disk & drum combi

Drew hereby the link to the picture of the cilinder which was on when I bought the car. I had it replaced with the same model.

http://www.c2registry.org/index.php?...og=1&wlr_id=24

[Drew P.]

Re: 65 - disk & drum combi

Hello Michael,
The photo is of a 1965 standard non power master cylinder.
Regards,
Drew Papsun

[Clem Z.]

comb brake systems would need a different

residual valve,to keep a light pressure on the front disk pads against the rotors, than a all disk brake setup. does GM list such a valve?

[Bill Stephenson]

Re: 65 - disk & drum combi

-----Drew is, as usual, correct as far as it goes. If your car had been a drum-brake car new it would have had a late 64 style master, as far as I have seen on other bonified drum-brake, non-power 65 Corvettes. Apparently, your car is way too late to be a delivered drum-brake car anyway, but now you know "the rest of the story"..........Bill S

[Michael H.]

Re: 65 - disk & drum combi

Bill,

The 66 parts book calls for a 64 style master cyl on 65's with drum brakes, just as you suggested.

[Gene M.]

my 65 drum brake car

Mike
I own a 65 coupe drum brake car #4403 base engine 3 speed. You are correct they have a standard production 65 frame. One thing I can add is the rear spindle is different from a disc brake car to keep the wheel position as mounted in the correct position as in 64 models. The drum at the mounting flange is thinner than the disk. This I presume is the difference along with the e-brake mounting on the trail arm assembly. The brake line attachment ear appears the same as the disc brake applications. I must admit that I don't recall any spindle differences in the front.

[Michael H.]

Re: my 65 drum brake car

Gene,

That's an interesting possibility. I never knew there to be a difference in the actual location of the flange on the spindle between drum and disc but it's certainly possible. I was told that the only difference was the length of the wheel studs between drum and disc but if that were the case, I suspect GM would have just eliminated the studs from both in service to make both parts the same part number.

I wonder what the actual difference is between the thickness of a drum web and the rotor web.

I think the drum brake front spindle is different than disc spindle and not interchangeable.

[John H.]

Re: Taking that a little further:

Michael -

You mentioned that your frame doesn't have indentations for rear caliper clearance; does it have the horizontal "keyhole" slot for sidepipe attachment directly below the rear lower corner of the doors on both sides? If it doesn't have the caliper clearance indentations or the keyhole slots, it would appear that the frame has been replaced with a pre-'65 frame.

[Wayne M.]

Gene - what about the other "markers"

like front X-member depression; keyhole for N14; frame indentation for caliper clearance; type of bumper bracket for matching trailing arm contact ?? Are you saying all these are standard '65 (as WITH disc brakes) ?? Are the trailing arms '65 DB type or '63-64 ?

To Michael H. I have both disc and '64 drum set-ups in the basement; will get a few dimensions for you.

[Wayne M.]

Here's a few dimensions

Comparing Jan '64 drum with a '65+ disc set-up. '64 spindle flange is thinner (0.332" vs. 0.450"); Studs extend less on '64 drum spindle (0.955" vs. 1.32"); Drum web thickness 0.125"; disc web 0.300" thk.

But there's much more figuring into the geometry; like caliper support bracket thickness; offset of caliper disc pad centerline from flange face (versus drum centerline offset).

I remember when I picked up my '65 (in 1989); I knew in advance that the original calipers were non-functional (boken bleeder, etc) so for the 1000 mile trip home I flew in with a set of good stainless. Proceeded to install when I realized that RR spindle was of '63-64 design; previous owner had inserted washers between spindle and disc to center disc in the caliper.