59 big brake or not? how to tell

[Ronald C.]

i recently picked up a 59 to try my hand at a c1 restoration. The car i settled on has been sittign for 8-10 years (death in the family). The window knew little about the car other than it has been in the family since 71. After an exciting trip to pick it up, rolling and totaling my truck on black ice i picked the car up. My question is i am finding some "interesting" things on the car and need to pick the brain of the experts:
1. the rear leaf is a 5 pack grooved. Will the original leafs have a stamped marking?
2. the drums are surely aftermarket but is there a difference in the brake show dimensions to indicate if they are big brake or standard?
3. due to body work needed there are no ducts however are there any indicators , holes to mount the dusts etc to look for?

[Jim L.]

Re: 59 big brake or not? how to tell

2. the drums are surely aftermarket but is there a difference in the brake show dimensions to indicate if they are big brake or standard?

Best thing you could do is post a picture of the drums and shoes on the car.

Regarding the possibility the car has aftermarket drums: I've never found (and I've looked long and hard for) aftermarket drums which would directly interchange with original big brake, finned drums. There are aftermarket drums which will interchange with the non-RPO drums and which are finned, however.

Big brake front shoes are 2-1/2" wide while standard shoes are 2" wide. Both fit drums with 11" inside diameter. Big brake shoes have friction material which is divided into separately attached segments. Standard shoes have friction material which is one, continuous strip

Bottom line: post some pictures. If you've got a big brake car, we'll know.....

Jim

[Mike M.]

Re: 59 big brake or not? how to tell

also include photos of the backing plates. mike

[Ronald C.]

Re: 59 big brake or not? how to tell

thanks guys will post,

[Loren L.]

Re: 59 big brake or not? how to tell

Does it have quick steering?

[John S.]

Re: 59 big brake or not? how to tell

Check the rear axle code. Stamped on the Pass. side of the axle frt.

Code:

AS 3.70:1 Manual Trans H.D. Brakes & Suspension
AT 4.11:1
AU 4.56:1

[James G.]

Re: 59 big brake or not? how to tell

JERRY WAGNER says
The 1957-58 RPO cars included a complex systems of ducts to lead cold air from the front of the car to the rear brake scoops. The 1958 rear ducting was more refined than that of 1957 in that it included 'elephant tusk' fiberglass ducts up high inside the front fender wells. These ducts were attached to the metal reinforcing straps that early '58s had in their front fenders. The base car fender reinforcements were dropped half way through the model year, yet, necessarily, '58 RPO cars retained them until the end of the model year.
Rear ducting was dropped in 1959 and the RPO cost was reduced by $355 as a result. Despite the Assembly Manual (AIM) not changing until October 17, 1958, the price dropped at the start of the model year and no '59s with rear ducting have not been reported. AIM dates are very rough approximations of when running changes were actually made. The rear duct outlets would have had clearance problems with the radius rods (traction bars) and their towers which were added in 1959. The metal rear air scoops were redesigned for 1959 and are flatter to clear the just introduced radius rods.
Late 1958 through 1962 RPO cars have two short ducts mounted on the fiberglass at either side of the radiator core support. These were to direct air to the front scoops mounted on the vented brake backing plates. 1956 and 1957 factory racers had triangular holes cut in their inner front fiberglass to accomplish the same purpose. The AIM date for adding these fiberglass front ducts was February 25, 1958.

In 1959 thicker, stronger front wheel hubs appeared on all Corvettes and gas-filled shocks replaced the earlier ones - both on base and RPO cars. The stronger hubs dropped the extra holes necessary to rivet the base front brake drums to them. The 1959 base brake drums also changed to a heavier, bell shaped design. The 1959 advance parts catalog shows that the new radius rods were not intended to be put on 1959 RPO cars, yet all seem to have them. Again this was probably due to interference with the rear ducting and when it was decided to drop the ducts, the go-ahead to install radius rods on 1959 RPO cars was given.


Brake Drums
All drums had the same casting number but there are four types, i.e., early and late, front and rear. The early drums have fins which wrap around the rim of the drum onto its outside face. The later ones began appearing in 1959 and have more squared-off fins which stop on the outer circumference of the rim.
The wraparound fins on early RPO drums protrude 1/8" from the drum face. The fins interfere with base 5" wheels where the flat attaching pads of the wheel center spider are welded to the rim. The optional 5.5" wide wheels fit fine. NOS early drums have been found with their front fins machined off by GM; this base wheel interference is most likely the reason the drums were redesigned. Another type of early drums had fins that protruded 1/2" on their faces and were designed for use with the Halibrand alloy wheels used mainly by factory racers.
The backside of all front drums have inner core braking surfaces which protrude 1/8" beyond the fins whereas the rear drums are machined flat, i.e., when set on a flat surface, the fins of rear drums touch the surface. The front drums have a more bell-shaped stamped metal face; the rears are flatter. An early '59 RPO car has been found with mixed drums, i.e., early ones on the rear and late on the front. Many RPO cars were raced and wore out their drums, so many '57 and '58 RPO cars also are found with mixed drums although originally they came with four of the early style drums. This is why early drums command a much higher price with collectors than do later drums.
Backing Plates
The 1957-58 backing plates have fine screen vents while the 1959-62 ones are coarser. The fine screens have 11-12 holes per inch while the coarse ones have 8 holes per inch. This change was made because the fine screens tended to clog up with dirt. Late 1958 and early 1959 RPO cars have been found with mixed screens.
RPO 684 rear backing plates have a washer welded onto them under the top brake shoe pivot pin to extend it. When the option was first announced in 1957, the specifications called for 1 3/4" rear shoes. Apparently when it was decided that the rear cerametalix shoes would be 2", the tooling for the backing plates had already been made. Consequently 2" rear shoes will not fit on backing plates that don't have a spacer under their eccentric pivot pin. Thus all 1957-59 RPO cars should have the welded spacing washers.
My early 1959 has fine screen front backing plates and coarse screen rears with the spacing washers welded onto them. This should put to rest the view that the screens changed with the 684-687 transition. RPO 687 rear backing plates have no washers. Very early 'prototype' vented backing plates (circa 1956) do not have rolled flanges, i.e., they are flatter around their circumferences. All front RPO backing plates are attached to the steering knuckle with tubular bolt spacers and bolts that are 1/8" longer than the base ones.

Brake Drums
All drums had the same casting number but there are four types, i.e., early and late, front and rear. The early drums have fins which wrap around the rim of the drum onto its outside face. The later ones began appearing in 1959 and have more squared-off fins which stop on the outer circumference of the rim.
The wraparound fins on early RPO drums protrude 1/8" from the drum face. The fins interfere with base 5" wheels where the flat attaching pads of the wheel center spider are welded to the rim. The optional 5.5" wide wheels fit fine. NOS early drums have been found with their front fins machined off by GM; this base wheel interference is most likely the reason the drums were redesigned. Another type of early drums had fins that protruded 1/2" on their faces and were designed for use with the Halibrand alloy wheels used mainly by factory racers.
The backside of all front drums have inner core braking surfaces which protrude 1/8" beyond the fins whereas the rear drums are machined flat, i.e., when set on a flat surface, the fins of rear drums touch the surface. The front drums have a more bell-shaped stamped metal face; the rears are flatter. An early '59 RPO car has been found with mixed drums, i.e., early ones on the rear and late on the front. Many RPO cars were raced and wore out their drums, so many '57 and '58 RPO cars also are found with mixed drums although originally they came with four of the early style drums. This is why early drums command a much higher price with collectors than do later drums.
Backing Plates
The 1957-58 backing plates have fine screen vents while the 1959-62 ones are coarser. The fine screens have 11-12 holes per inch while the coarse ones have 8 holes per inch. This change was made because the fine screens tended to clog up with dirt. Late 1958 and early 1959 RPO cars have been found with mixed screens.
RPO 684 rear backing plates have a washer welded onto them under the top brake shoe pivot pin to extend it. When the option was first announced in 1957, the specifications called for 1 3/4" rear shoes. Apparently when it was decided that the rear cerametalix shoes would be 2", the tooling for the backing plates had already been made. Consequently 2" rear shoes will not fit on backing plates that don't have a spacer under their eccentric pivot pin. Thus all 1957-59 RPO cars should have the welded spacing washers.
My early 1959 has fine screen front backing plates and coarse screen rears with the spacing washers welded onto them. This should put to rest the view that the screens changed with the 684-687 transition. RPO 687 rear backing plates have no washers. Very early 'prototype' vented backing plates (circa 1956) do not have rolled flanges, i.e., they are flatter around their circumferences. All front RPO backing plates are attached to the steering knuckle with tubular bolt spacers and bolts that are 1/8" longer than the base ones.

Brake Springs
All RPO 684-687 cars used pullback springs which are Dark Green and although the same diameter as base springs, they are stronger and much more heat resistant. RPO 686 pullback springs have a larger diameter and were never used on 684-687 cars.
Until RPO 686 was offered in 1959, the RPO 684 cars used base springs for the hold-down pins, adjustors, and parking brake struts. The RPO 686 metallic brake hold-down springs were also used with RPO 687; they are Avocado Green and their inside retaining washers are larger and flatter than the outer cups which appear like base ones. The correct hold-down pins are set forth below. The number is stamped on their head and their length is shown below:

	Front	Front	Rear	Rear
Base Cars	#4	2"	#8	1.875"
RPO 684	#6	2.25"	#4	2"
RPO 687	#6	2.25"	#8	1.875"

Mike Ernst (see Restorer; Volume 17, #4; Spring 1991; pages 28-32) has noted that the adjuster springs should be Black on the front and Baby Blue on the rear of 1960-62 RPO 687 cars. Base adjustor springs are Dark Blue and were used on most RPO 684 cars. The nuts (female part) and sockets of the RPO brake adjusters carry a different part number than base ones; they appear about 1/16" longer.
Brake Cylinders
The base front wheel cylinders were 1-1/8" in 1957-59 and 1-3/16" in 1960-62. RPO cars kept the 1-1/8" front cylinders all the way through 1962. The RPO rear cylinders are 7/8" as opposed to the 1" base ones. The part numbers for RPO 684 rear cylinders are 5456398-399 and show casting number 5456400. Cylinders cast 5456400 look as large as 1" cylinders but are actually bored only to 7/8". RPO 687 rear cylinders show a casting number of 5450996 and were assigned part numbers of 5459986-987. They are cast as true 7/8" cylinders and smaller on the outside than the earlier RPO 684 cylinders.

[Ronald C.]

Re: 59 big brake or not? how to tell

Many thanks James this is the information i need to really complete a good investigation. Based on what you provided above i think the brakes are all after market. the car appears to have been raced. I have spoken with the last owner back to 1971 and there was no racing at that time so it must be the original owner...still trying to track down the family. The car shows clear signs of:
- 5 leaf springs but not original
- modified lower shock mount. leaf plate
- a larger tank mounted in the truck. modified truck so tank was mounted to frame. and modified trunk lid
- modified bump stops for wheel travel
- spring rubbers. 2-3 on the drivers side front and 1-2 on the passenger side
- different front springs then original
- a "c" plate mounted about mid door extending 1"up the frame and down about 2" -3"; no evidence of frame damage. I can only speculate it is to allow for a jack on the side of the car to remove side tires only. and to prevent the jack form crushing the frame rail at the weld joint.
- and then there are the engine and rear end modifications for more horsepower/speed. using 1961-1962 parts

I hold out hope ill find owner 1 and learn more

[Gary C.]

Re: 59 big brake or not? how to tell

Ron,

What is the stamping on the rear spring lowest leaf. There should be a part number and julian date visible, but the stamping might be under the shock plate.

Sounds like the car has a bunch of intriguing mods. Photos are always helpful. The more the merrier.

Gary
....