69 RF brake lock up?

[jvb6648]

Jim, Do you have access to a couple of scales, maybe a highway patrol or trooper friend who works truck inspections. You mentioned that this was a drag car for a while. If the body is twisted it could make the R/F light and make less work for that brake causing the lock up.
Jim

[Rufcar]

With just about everything replaced Im taking time to re
think what my next step is. I will let everyone know how I make out in the up coming weeks. Happy holidays to all!

[Dave Siltman]

Did you ever measure the wheelbase from side to side? Back in the '80s we "staggered" the front wheels in my Chevelle drag car to get about an inch and a half more rollout in the starting beams. If you slammed the brakes and weren't ready for it, the car would dart to the right because that front wheel was set back farther than the left. I'd try measuring the centerline from side to side and then get the car in the air and get it "squared". If for nothing else, it might eliminate something else from the equation.

[Rufcar]

Dave I didn't actually measure the front but I have set up on a 4 wheel alignment machine. It was a dag car years ago but I figured the 4 wheel adj would catch that? 
After I wrote that paragraph I took the old girl out for a drive and after my last plumbing which was to put the left wheel into the larger hole of the distribution block on fender side and the RF to the engine side and smaller hole and the MC to the front center hole the car was much better. I drove on back roads and braked a lot and as long as I didn't HIT the brakes but only pushed on them the car was fine. Though even at slow speeds, like approaching a light if I pushed a bit harder it would lock up and release. The way it is now seems to work better then it ever did though not perfect. Since it is a 4 speed with huge torque and compression the car always slowed easily. I can def live with it like this or until I find the answer. Tkx Guys! Jim

[HustleRussell]

Hi Jim. Have you made any progress? I was having similar problem with my 1997 GMC truck and thought I'd share how I fixed it.
One rear wheel cylinder was leaking. So I replaced both. Brakes worked fine until the humidity got really high or during rainy spells.
That's when barely touching the pedal right rear would lock up. After the humidity and storms passed it would go back to working fine.
I thought it might have something to do with the brake fluid that had been absorbed into the brake shoe. I switched the shoes from one side
to other side. Sure enough during the next rain the left rear would lock up barely touching the pedal. Replaced both sides with new shoes.
Haven't had any issues since.

[Rufcar]

69z27, I did have a rear leak in new cylinders and changed that one re adjusted both right front still locks up. I sort of gave up as I changed everything and it made no difference.  I have been driving it that way now for close to 5k mi. I know how to stop without locking by just slowing down gently. 

[myblue67]

Did you reach any conclusions? Similar problem. A new master cylinder fixed the problem for about three months...now returned. Hard to believe it is a MC again.

[Rufcar]

Sorry I have not been on all summer. I was completing my 70 Chevelle full restoration, also did a 71 Rolls coupe and just now finished a 89 Jeep YJ. I drove the Camaro approx. 1000 mi this summer with the brake problem. I have replaced and tested every brake component and in the end nothing helped! RF still locks up under light pressure. I even gave the car to another 40 yr experienced mechanic who swapped and tested everything and accomplished nothing. Spoke to several experienced muscle car specialist around the US and to date its still exactly the same. So for now It will stay like it is as I can drive around it and have for 4 years now. Over the winter I may go it once again. Tkx Jim F

[Rufcar]

A final follow up on my continuing right front brake problem. If you read back you will see I replaced every brake component that was new when I bought the car 5 years ago. I have learned much that all said in the end I bought a USA made Pressure control valve and inserted between the MC and the RF brake and set at almost zero it solved the problem of the RF brake always locking up and to recap. Not only did I change every component I swapped the left to right and back again. I also swapped right to left line and back again. I ran new temporary lines and absolutely nothing make a any difference.
After finally finding someone who understood why its happening but not how to instantly repair it. Its due to quality control of imported parts. Lines, calipers, rotors etc are not all machined in matching sets or to a high standard and there lies the problem. Tkx for all your suggestions over the years!

[mikefam]

What condition are the front right pads in? Is the caliper piston over-extended?

Mike.

[Rufcar]

Mike you really should read everything from page 1 on.  . I replaced every component and nothing made any difference. My inline pressure control valve solved a 4 yr puzzle.

[67 RS Ragtop]

Glad to hear your issue has been corrected, as Safety is always first and foremost. I did wonder if you ever verified the application pressures at both front wheels (I didn't see mention of the pressures). If I had known they were the same i would have suggested having both rotors re machined and the pads burnished in to see if any changes were made. At any rate, glad your problem has been solved.

[Kelley W King]

My 64 vette  with power drum brakes does the same thing cold. A few stops and it is fine.

[Rufcar]

I did buy 2 different sets of brake pressure testing gauges and the problem was the fittings/adapters. I even bought a box of 6 different adapters and none worked up front but did in the back. So I did make my own adapter . The next problem was I kept getting 350 lbs so they appeared the same. I then installed the valve, solved the problem, and then  realized I did not have the engine running to create the proper pressure! Ya go ahead and laugh , wait to your 69 years old! lol

[67 RS Ragtop]

Not laughing, as I am older than that, just don't know how I got here.