63 SWC: Advice on Brake Changes

[Duke W.]

Re: 63 SWC: Advice on Brake Changes

I like using DOT5 silicone fluid for brakes, even used it when I rebuilt a hydraulic operated clutch pedal. One thing to think about is in using the original type drum brake brake shoe linings that will use the same composition as originals for best braking. I use Bendix original type composition.

The original friction materials that contained asbestos are long gone since asbestos was outlawed in the seventies, but friction material manufacturers have come up with non-asbestos friction materials that essentially duplicate the performance characteristics of the old asbestos-based materials.

The base brake system is more than adequate for any normal road driving, and any name brand replacement shoes should be the equal of the OE base brake shoes.

If one plans to do some canyon carving or race track hot-lapping, contact the company in the following link. They offer a material that has the fade resistance of the old metallic linings, but with a much more consistent friction coefficient over the operating temperature range, so they don't require very high pedal effort the first few stops in the morning until they warm up.

http://www.ctbrakes.com/pads.asp

Duke

[Joe L.]

Re: 63 SWC: Advice on Brake Changes

Maybe I missed something earlier. Have you actually measured your mc? According to my 63 factory service manual standard and power brakes used the same 1" bore, the hd metallic brakes used the 7/8". You'd be fine using either one of those.

Yes, redid my math this morning and I don't know how I ended up with 50%. I should know better than to do arithmatic after happy hour.

Steve------


I think the service manual is incorrect on this. I believe all 1963 used a 7/8" master cylinder except HD brakes (J-56).

[Harry S.]

Re: 63 SWC: Advice on Brake Changes

Steve------


I think the service manual is incorrect on this. I believe all 1963 used a 7/8" master cylinder except HD brakes (J-56).

J56 was not a 63 option. It was imbedded in the Z06 Option. J56 became available in 64.

Saying that, I agree with Joe, all 63 Master Cylinders outside of Z06 were 7/8".

[Duke W.]

Re: 63 SWC: Advice on Brake Changes

'



The 1963 Corvette Shop Manual says base brakes have a 1.0" m/c and metallics (J-65) is 0.875".

63 AMA specs say 8.75 for all - obviously an error in decimal point placement in addition to possibly diameter.

'64 AMA specs say .875 for base, J-50 and J-65. The implication is that the same .875" bore was used for both manual and power brakes with both base and J-65. So that would mean only two M/C were used in production - one for manual and one for power brakes, and presense or absense of the J-65 option had no bearing on the installed M/C .

Since the AMA specs were updated with production changes and error corrections, I believe the AMA specs data.

Duke

[Steve G.]

Re: 63 SWC: Advice on Brake Changes

'



The 1963 Corvette Shop Manual says base brakes have a 1.0" m/c and metallics (J-65) is 0.875".

63 AMA specs say 8.75 for all - obviously an error in decimal point placement in addition to possibly diameter.

'64 AMA specs say .875 for base, J-50 and J-65. The implication is that the same .875" bore was used for both manual and power brakes with both base and J-65. So that would mean only two M/C were used in production - one for manual and one for power brakes, and presense or absense of the J-65 option had no bearing on the installed M/C .

Since the AMA specs were updated with production changes and error corrections, I believe the AMA specs data.

Duke

I would buy that (.875) for everything over .875 for power or manual organics and a 1.0 with 30% greater pedal effort required for brakes with a known lesser coefficient of friction.

I would still urge the op to take it off and measure it. If it were an original MC it would tell us which is correct.

[Joe L.]

Re: 63 SWC: Advice on Brake Changes

I would buy that (.875) for everything over .875 for power or manual organics and a 1.0 with 30% greater pedal effort required for brakes with a known lesser coefficient of friction.

I would still urge the op to take it off and measure it. If it were an original MC it would tell us which is correct.

Steve------

It certainly can't hurt to measure it assuming it's off the car.

However, if a 1" bore master cylinder was ever used for 1963 (except HD brakes), then that master cylinder was NEVER available in SERVICE. The only master cylinders available for 1963 (except HD brakes) in SERVICE were 7/8" bore.

[Steve G.]

Re: 63 SWC: Advice on Brake Changes

Steve------

It certainly can't hurt to measure it assuming it's off the car.

However, if a 1" bore master cylinder was ever used for 1963 (except HD brakes), then that master cylinder was NEVER available in SERVICE. The only master cylinders available for 1963 (except HD brakes) in SERVICE were 7/8" bore.

Was the 1" actually used on the 63 at all? From what Duke posted all 63 mc's were 7/8. It just doesn't make sense that they would use a larger bore on the brakes that already require more pedal pressure.

[Joe L.]

Re: 63 SWC: Advice on Brake Changes

Was the 1" actually used on the 63 at all? From what Duke posted all 63 mc's were 7/8. It just doesn't make sense that they would use a larger bore on the brakes that already require more pedal pressure.

Steve-----


The 1" bore master cylinder was used on 1963's with HD power brakes (J-56). This was a special, dual circuit master cylinder manufactured by Kelsey-Hayes. One doesn't want to need one of these master cylinders.

By the way, the 63-64 HD brake master cylinder was the only master cylinder manufactured by Kelsey-Hayes that was EVER used on a Corvette. A total of 228 cars ever received one.

[Harry S.]

Re: 63 SWC: Advice on Brake Changes

Steve-----


The 1" bore master cylinder was used on 1963's with HD power brakes (J-56). This was a special, dual circuit master cylinder manufactured by Kelsey-Hayes. One doesn't want to need one of these master cylinders.

By the way, the 63-64 HD brake master cylinder was the only master cylinder manufactured by Kelsey-Hayes that was EVER used on a Corvette. A total of 228 cars ever received one.

Correct, 199 in 1963 as part of the Z06 option and 29 in 1964 as an ordered option (J56). It was not offered in 65.

[Jason S.]

Re: 63 SWC: Advice on Brake Changes

'



The 1963 Corvette Shop Manual says base brakes have a 1.0" m/c and metallics (J-65) is 0.875".

63 AMA specs say 8.75 for all - obviously an error in decimal point placement in addition to possibly diameter.

'64 AMA specs say .875 for base, J-50 and J-65. The implication is that the same .875" bore was used for both manual and power brakes with both base and J-65. So that would mean only two M/C were used in production - one for manual and one for power brakes, and presense or absense of the J-65 option had no bearing on the installed M/C .

Since the AMA specs were updated with production changes and error corrections, I believe the AMA specs data.

Duke

The AMA specs I have revised November 1962 indeed say the base single reservoir MC has a piston diameter of 0.875 and the piston(s) on the HD Z06 package had 1.00. Indeed, as pointed out elsewhere in this thread, that agrees with the base MC's sold for service at 0.875. For J65 by itself - it has no mention of piston bore in any master cylinder specs either way.

I wouldn't necessarily say I'm trying to "cobble" a dual master into the car - several vendors sell the kit with a '67 dual MC and all the matching pre-bent stainless lines. It's a kit I'll be buying - not cobbling together whatever I have laying around the garage. But with that said....since these conversions use the '67 part, it will be a 1" bore. Hence why I'm expressing the concern about pedal effort.

I agree that a perfectly maintained brand new single-pot brake system should operate just fine - but in the event a leak or other failure happens, a single-pot system will be DONE in one pedal jab. GONE. That's what got my car sidelined - a pinhole leak in an otherwise immaculate looking brake line. I don't want that to happen again. I think there is a reason why the DOT mandated these systems after 1967 or so......

Basically, if I'm going through the brake system from beginning to end, I think the dual circuit system will be safer/more bullet proof. In fact.....in original GM bulletins from the era they themselves make the claim that the Z06's Dual-Circuit system is "safer" in the case of any brake issues (I wish I could find the original text right now to quote it).

[Jason S.]

Re: 63 SWC: Advice on Brake Changes

Maybe I missed something earlier. Have you actually measured your mc? According to my 63 factory service manual standard and power brakes used the same 1" bore, the hd metallic brakes used the 7/8". You'd be fine using either one of those.

Yes, redid my math this morning and I don't know how I ended up with 50%. I should know better than to do arithmatic after happy hour.

Also - referring to page 151 of "Corvette Restoration Guide 1963-1967" it says in the Basic Drum Brakes section "this master cylinder has a 7/8-inch bore, which is why 7/8 is embossed on the front of the casting..."

On page 77 of Noland Adams' restoration guide, "The standard brakes on 1963 Corvettes used a master cylinder with a 7/8-inch piston" and "when equipped with the J50 power brake option (power brakes) the same cylinder was mounted on a vacuum booster canister". Starting on page 176 under Z06 equipment, it states "Z06 brakes were power assisted, with a special dual-circuit master cylinder. Sintered metallic linings were matched to heavy-duty finned cast iron brake drums" and "A power brake servo was available separately as option J50, and metallic brakes were option J65. There is some confusion here, since these options are often thought to be part of option Z06. But they are not the same at all. For example, the master cylinder and power brake boosters supplied with J50 and Z06 are quite different. And so are the brakes themselves: J65 drums were finned, similar to Z06 drums, but the Z06 shoes were larger."

Indeed.....so here's the punchline....a pic of my master cylinder casting:
IMG_3166.jpg

[Duke W.]

Re: 63 SWC: Advice on Brake Changes

J-65 drums are not finned. They are the same castings/casting numbers as the base system drums, except the front drums have slightly thicker webs, which are hand stamped with an "X" to ID them. The finished part numbers are different for this reason and the fact that the wear surface has a finer finish as explained in the 1963 Corvette Shop Manual.

Duke

[Stuart F.]

Re: 63 SWC: Advice on Brake Changes

I replaced my sintered metallic linings over 4 years ago with a material called Matrix Ceramic from an outfit in Texas called "Praise Dyno Brake Company". They have worked fine since with performance equal or better than the metal pads, including stopping in the morning like Duke referred to in an earlier post. I recently changed the fluid again as I use DOT 4.

I lost my metal brakes due to corrosion both with the pads rusting/breaking off the shoes and my right front wheel cylinder drowned in water. The linings all looked good on this inspection and all the hydraulics are holding up fine here in humid and hot central Florida.

I also installed a correct 63 MC along with the linings. It's a sleeved 7/8" I'd. I had been getting along with a 64 unit with a bail held cap for a number of years as my original was stolen by a shop in Illinois.

Stu Fox

[Michael G.]

Re: 63 SWC: Advice on Brake Changes

While a dual circuit system is clearly safer than a single circuit, (all other things being equal), I don't think I'm going out on a limb here by suggesting that using a stock single circuit system is a lot smaller risk than making changes to such a well validated system without doing the appropriate amount of testing and validation. Its absolutely not a good idea to invent a braking system and not test it extremely thoroughly (as GM did) before use.

Frankly, the stock single circuit system is very safe, when its in good shape, as yours will be. An awful lot of Corvettes were driven a heck of a lot of miles with the original system. I'd rebuild it thoroughly and leave it stock.

[Jason S.]

Re: 63 SWC: Advice on Brake Changes

While a dual circuit system is clearly safer than a single circuit, (all other things being equal), I don't think I'm going out on a limb here by suggesting that using a stock single circuit system is a lot smaller risk than making changes to such a well validated system without doing the appropriate amount of testing and validation. Its absolutely not a good idea to invent a braking system and not test it extremely thoroughly (as GM did) before use.

Frankly, the stock single circuit system is very safe, when its in good shape, as yours will be. An awful lot of Corvettes were driven a heck of a lot of miles with the original system. I'd rebuild it thoroughly and leave it stock.

I'm starting to come back to that perspective - i.e., rebuilding with it still in correct stock configuration. But hopefully you can understand why I'm so gun-shy. When the brake system failed previously due to that brake line pin-leak, it was luckily in my drive-way. I'd hate to have such a thing happen at 60 mph out on a road way. Now if I could just get my hands on a Z06 master cylinder and booster, this conversation would be easy and done .