Greetings. I am working on replacing brake shoes on my 1954 Corvette and having difficulty with the initial adjustments I was hoping someone could give me a pointer or two. Aside from any brake bleeding issues at this point I did not have a firm pedal at all until I began adjusting the shoes. with the hubs on of course I pumped the pedal a couple of times to center the shoes, then adjusted the wheels until they were tight, pressed the pedal again to centralize and then backed off the star adjustment until there was a slight drag - equal on both rear wheel. Put the tire on and one of the wheels was locked up so I backed off a couple clicks and the wheel turned a bit and then locked again, but I could spin the tire backward then it hung up again. Was just wondering looking at the old shoes they had a slight 45 degree chamfer of the leading edge of the linings. Perhaps the edge of the new shoes are catching and causing the issue. Don't want to go down this rabbit trail is it has no bearing on what may be my approach to adjusting is wrong. Any suggestions most appreciated - especially on correct adjustment procedure of the new brakes. Thanks, John
You are following the right process to adjust them. You are correct about the importance of getting the shoes centered in the drum.
My thinking is that the drums are worn slightly out of round. You can confirm this by noting the position of the wheel when it catches or drags.
I doubt if the chamfer has much to do with this. You could file or sand a slight chamfer but I doubt if that will make a difference.
The other issue you deal with when putting new shoes on old drums is that the radius of the shoes is slightly smaller than the radius of the worn drum. The shoes were made to match the inside diameter of a new drum. Your new shoes do not touch the drum uniformly. With some miles and usage things will wear to better match unless the drums are really worn or you have to turn them oversize to get rid of the out-of-roundness. Some brake drum turning machines also had an attachment to “arc” the shoes to match the oversize drum. It does remove material from the shoes which shortens their life. However I doubt if you will ever drive that car enough to wear put the brakes.
Thank you Rusty for your insights on the brake shoes. it makes sense they would need to be worn in over time.
Seems I am trying to tackle too many issues at once. Still having difficulty in getting a firm pedal even after many attempts of bleeding the system. Have done the 2 person method and even tried the Motive pressure bleeder. absolutely no bubbles in fluid after a couple rounds resulting in a very firm pedal but then overnight I come back and the pedal goes almost to the floor but with a couple pedal pumps the pedal firms up. Bench bled the new master cylinder but I am thinking there is still air in the cylinder or system.
I may need to give this a rest for several days, I am close to burn out. Can't be that difficult, but then again most of my previous brake work was on the old 31' Chevy. Did not have to contend with air in the system ha. John
Sorry to hear that you are having multiple issues with the brake system.
Have you checked to confirm that there is a very small clearance between the pushrod and the piston in the master cylinder when the pedal is released? That clearance is essential to ensure that the piston travels all the way to the home position and allows fluid to come back into the reservoir.
I do not know how that is adjusted on your Corvette. On the older Chevy’s and many other cars there is an eccentric bolt in the brake linkage that allows you to set what the shop manuals call “toe board clearance”. On my Miata the pushrod was threaded into a clevis with a locknut. You would loosen the locknut and turn the push rod until you just felt it hit the spherical seat in the end of the piston.
I completely appreciate the need to “walk away” from problems like this. You can create more problems and frustration if you keep pushing.
Here is one test I would consider. After you have a firm pedal, adjust all the brakes until you cannot rotate any of the wheels. Let it sit overnight and see how the brake pedal responds the next day.
One other idea to consider is that perhaps you do not have e a good seal in your master cylinder or one of your wheel cylinders is weeping slightly. Unfortunately my experience is that “new” does not necessarily equal “good” for replacement parts these days.
Thanks Rusty, I had the master cylinder rebuilt by White Post so looking at the push rod it is just a pushrod with the eyelet on the end, no threaded adjustment, that being said I will check tomorrow on the pedal assembly itself to see if there is pedal travel adjustment in that system.
I checked once more all of the line and hose fittings, I installed new copper crush washers on the hoses where needed. pulled wheels to see if there was any sign of leakage (easy to tell since all is newly painted) no leaks. I tightened all of the wheels so I could only turn them with effort. Checked the pedal.
Pedal travel was firm. I have 5" between the back of the pedal and the floor. Right now with the brakes adjusted tight a firm pedal is felt with the back of the pedal between 3-1/2" - 4" from the floorboard. Not bad, but then the brakes are fully tight. Will see what the outcome is when I check the pedal in the morning - if it goes to the floor and then a couple of pumps of the pedal brings it back to firm.
Going back too many years, working in my Dad's repair shop, I remember a local parts store with a machine shop in the back. Dad sent me there to have brake drums turned. The counter man brought in the brake shoes and the machinist chamfered the top and bottom of each and fit them to the drums so that the entire brake shoe made contact with the drum. During this time period, I would finish the brake job and off would go a satisfied customer.
A few years later the machinist retired and the parts store sold off the equipment. Dad had told me he wished he had bought that one machine. He searched for one but no one had one and the newer machine shops didn't have that service.
The down side was, Dad would have to explain the way self adjusters worked to the customer so that as the top and bottom of the brake shoes wore down the pedal would stay relatively firm. More often then not, a few weeks later the car would come back with a low pedal.
As I became more interactive with customers, I would tell them to come back in 2 weeks and I would readjust the brakes after they "broke" in.
Nostalgia ...
Dave old cars are meant to be driven !! VCCA # 047832
