2 C-2 Drum Brake Questions

[Richard W.]

I have 2 questions re my driver SWC drum brakes.

First, while I am satsified with my drum system, I am concerned about the single master cylinder. I figured GM or Uncle Sam didn't go to a dual system for the heck of it. Am I being too paranoid? What is the best/easiest conversion to make (i.e. which year/type should I use)? Any tips on converting?

Second. I just rebuild the front end (major kit and replaced the front brake hoses) and the car pulls to the right side. Before the rebuild it pulled to the left. The alignment mechanic said the wheel cylinders need to be replaced. Any suggestions as to new cylinders or rebuld the existing ones?

Thanks in advance.

[Duke W.]

Re: 2 C-2 Drum Brake Questions

I believe the industry went to dual circuit master cylinders in 1967 because it became a FMVSS. A very few might have had dual circuit systems prior to that.

The reason why master cylinders fail is almost invariably corrosion of the bore and this is because owners do not flush the system out periodically, so moisture builds up and causes corrosion. If you flush the system out every couple of years, a master cylinder failure is unlikely. I've also heard of both circuits on a dual circuit system failing simultaneously, so they are not guarantee of being able to stop. If the pedal goes to the floor you can usually pump it up, and then there's downshifting and the parking brake. It never hurts to bone up on your emergency procedures.

Pull might be caused be either unequal caster or camber. More than about 1/2 degree of cross camber or caster can cause pull. They should always be set as close to equal on both sides as possible. Pull can also be caused if a leaky wheel cylinder allows brake fluid to get on the linings. Once organic linings are soaked, they history, but I've managed to save metallic linings by thorough soaking and rinsing in water.

Wheel cylinders are inexpensive and kits are even cheaper. If you want to rebuild them, a careful inspection of the bore is necessary. If there are any significant pits, they should be replaced. Very minor corrosion that can be cleaned up with a light hone are okay to reuse.

If you buy new ones you can just bolt them on and be confident that they will work. New or properly rebuilt hydraulic components and a complete fluid flush every two years should keep the hydraulics in good shape as long as most of us will be around to worry about it.

Duke

[Wayne P.]

Re: 2 C-2 Drum Brake Questions

And don't forget to adjust the shoes!!

[Mike M.]

Re: 2 C-2 Drum Brake Questions

duke's post is right on. only thing i'd add is the whel cyl and master cyl can be stainles sleeved then you nefver have to worry about H2O in the brake fliud pitting the bores of the cylinders. Stainless steel brakes in clarence N.Y. is where i send cylinders and calipers for sleeving.good luck, mike

[Joe L.]

Re: 2 C-2 Drum Brake Questions

Richard-----

The very first Corvette to receive a dual master cylinder was the 1963 with Z-06. After that, the next Corvettes to receive such a system was the 1965 with power brakes and the 1966 with power brakes. The 65 system was designed for use with disc brakes only (the few 65's built with drum brakes got the 64 style master cylinder if they also received power brakes). So, as far as dual-circuit master cylinders used with drum brakes, the 63 Z-06 system was the only one ever. There are usually slight differences in master cylinders used for disc brake systems versus drum brake systems. Primarily, the difference involves internal check valves in the master cylinder output for drum brake circuits. As far as I know, no "hybrid" systems (never used for Corvettes but for other cars; front disc, rear drum) were ever built with a single circuit system.

It would be possible to convert your system to a dual-circuit brake system. However, I wouldn't recommend it. What you'd gain in braking system safety would be off-set by the "vagueries" incumbent in the conversion. A well-maintained single-circuit system should be quite safe.

As far as the alignment man's contention that wheel cylinder problems are causing the pull, he could be correct, but likely ONLY if the cylinders are actually leaking. If they aren't leaking, then the pulling problem lies elsewhere.

I don't recommend the rebuilding of wheel cylinders if any honing of the bores is required. If honing is required (and it almost always is), I recommend replacement of the wheel cylinder or sleeving of the wheel cylinder. Usually, sleeving of the wheel cylinders is not a cost-effective solution unless the wheel cylinder is not obtainable in new condition.

[Chuck Swenson]

Re: 2 C-2 Drum Brake Questions

I replaced all my lines with stainless and all brake components. Nothing is old, so I refilled with synthetic DOT 5 brake fluid to hopefully eliminate H2O. I wasn't planning on flushing every 2 yrs when using the synthetic.
Chuck

[Richard W.]

Thanks to all for responses--1 follow-up question

The car pulled to the left before the rebuild. At times the brake would grab at very low speed. My mechanic said it was caused by worn suspension components and, in fairness to him, a lot of the left side stuff was pretty well shot. I did the ball joints, tie rod ends and sleeves, idler arm and rebuilt the center link. The car now pulls (with brake grab) on the right. This was present before and after trip to alignment shop.

The alignment guy (very experienced and older than dirt), thought it was brake hoses so I had him replace ,which he did but did not help. He then suggested wheel cylinders (I can't remember if he said one or both were leaking and I don't remember seeing anything when I had the brakes off). I did not remove the brakes from the hoses when I did the rebuild (just tied back the spindle). He also suggested changing flushing and changing the fluid since it was pretty bad. One last thing, it seems to help for a short time if I back the car up several times.

My follow-up question, if the cylinders are not leaking, where best to look.

Thanks again to all.

[Dave Suesz]

1 follow-up question

Pull the drums, peek inside the dust caps.

[Duke W.]

Re: Thanks to all for responses--1 follow-up quest

"One last thing, it seems to help for a short time if I back

the car up several times."

The above implies an adjustment issue. The self-adjusters activate when the brakes are applied in reverse. If shoe travel is sufficient the adjuster lever bumps the star wheel a notch. The adjusters should be removed, disassembled, cleaned and lubricated with a dry lubricant. Lock-Eze would work as it is an emulsion of graphite in a petroleum distillate, which evaporates.

Inspect that the star wheel teeth and tang on the adjuster lever are not worn to the point where the tang cannot engage the star wheel teeth to adjust the brakes.

Duke

[Dave Suesz]

Oops-never mind-misread the question *NM*

[Mike McKown]

I would look for sticking wheels cylinders as well

If you have a piston(s) stuck on a cylinder, it will not exert the same pressure at the opposite cylinder if it is not in like condition. If your alignment man is experienced, he will know this and he will also know that adjustment will cause the same problem, though to a lesser extent. That may explain why backing up makes the problem somewhat better for a time. When you back up and apply the brakes, they are adjusting themselves.

Quality wheel cylinders can be purchased for around $10. Used ones generally aren't worth rebuilding for that price.

[Joe L.]

Re: I would look for sticking wheels cylinders as

Richard and Mike-----

Yes, I agree. After all you've done to correct this problem, I'd just go ahead and replace the wheel cylinders whether they're leaking, or not. It's not a very difficult job and, as Mike says, they're cheap. Always save the originals, though, IF they are, indeed, originals. At this point in the car's life, they could have already been replaced one or more times previously.