61 Corvette - Weak Brakes

[scuncio]

Hi folks,

Working on my dad's '61, and it's become apparent that the brakes are just not up to what I'd consider a 'safe' level of operation. I had the original MC rebuilt by White Post ~15 years ago, and installed new shoes and flex lines at that time. I didn't touch the wheel cylinders, as they showed no signs of leakage. The brakes don't exhibit any pull to one side, but the stopping power is extremely weak - I can't lock them up under any circumstances, and the pedal feel isn't confidence inspiring.

I know these brakes are not self-adjusting. Should I start there first, and re-adjust each star wheel? Any advice would be appreciated.

[napa68]

Tony,

Have you bled the system yet? These systems respond well to a good old gravity bleed. Don't let the lack of self adjusting mechanisms get in your head. These systems work well, just a little different fundamental.

Check to see if the pistons in the wheel cylinders are froze. They won't leak, but won't brake properly either. It's a simple system as you know.

Tim

[Too Many Projects]

Do you recall if the brakes worked good after the "renew" 15 years ago ?

If they did, I'm on the same page as Tim with stuck wheel cylinder pistons. You could start by adjusting the shoes out for proper contact, but if they don't take much adjustment, then you're probably looking at the pistons.
Also, what fluid did you use after the renew ? and did you run enough thru the system to purge all of the old ?

[Steve Shauger]

I think I have the same issue with my unrestored 67 Camaro, which has manual drums. I apply pedal pressure not much response. If I apply a lot of pressure the rear wheels will lock up. Last I worked on the brakes was 1996, at which time I sleeved the master and believe rebuild wheel cylinders.. I sold it in 2004 and was reunited in 2017. Seems to have gotten worse. I have nos front lines and believe the fronts are the issue.

[TWB]

There is no reason why a properly operational brake system on that car should be inadequate. Same size drums and shoes were on much heavier GM cars. New wheel cylinders are available and you may want to replace them with the hoses. Be sure drums and shoes aren’t glazed.

[juliosz]

I guess all four wheel cylinders could be stuck but I believe you indicated the car stops straight but lacks stopping power, correct? If that’s the case, maybe master cyl is the problem?

[scuncio]

Thanks, guys, appreciate the good ideas so far. I'm suspecting it's the master, but will bleed it tonight and see if there's any improvement. It never stopped well after the brake refresh years ago. I used DOT 3 and a LOT of it so I'm confident all the old fluid would have been pushed out.

[Too Many Projects]

Originally Posted by scuncio

Thanks, guys, appreciate the good ideas so far. I'm suspecting it's the master, but will bleed it tonight and see if there's any improvement. It never stopped well after the brake refresh years ago. I used DOT 3 and a LOT of it so I'm confident all the old fluid would have been pushed out.

Dot 3 is good, not stopping well after the refresh isn't. As Julio said, the no pull situation could point to the master.

[PeteLeathersac]

‘

Sounds like you’re on the right track, way cool it’s your Dad’s 61!
If you haven’t seen it yet, here’s a link to the original GM Communication film w/ info on how the new for ‘63 Self Adjusting Brakes work also updating older systems to the new style…
https://www.youtube.com/watch?v=T6qTqJ-tdrE&t=17s


~ Pete

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[scuncio]

Finally bled the brakes tonight using the gravity method that I typically never use. Worked like a charm, thanks Tim, I owe you one! Going to the employee car show this Wednesday and going to swap out these radial redlines for a set of Polyglas tires. Can't wait to improve this car a bit at a time.