When I converted my 1964 Impala to have front disc brakes, I thought I was going to have great brakes for minimal time, money, and effort. Instead, I had endless pain and suffering for months, and no brakes.
I started off with a disc brake kit that came with a set of brackets to mount the calipers to my stock spindles, Camaro calipers, Chevelle? rotors and bearings, and new brake hoses. I didn't order the dual reservoir master cylinder and proportioning valve at the time, because I figured I would get them cheap locally. Either way, with minmal money, and time I was going to swap my old (great working) drums to the "newest" technology known as disc brakes.Round #1:
Over the next weekend, I picked up the good, used, working dual reservoir master cylinder, proportioning valve, and installed the whole disc brake setup on my Impala. To my surprise, when I was done, the brake pedal hit the floor. I thought to myself..."This is very odd". I then bled the master cylinder again, the rear brakes, the front brakes, the proportioning valve, and pushed the brake pedal. Sure enough, it hit the floor with the wheels still spinning. I could see both caliper pistons move when the pedal is pushed, but they dont come out enough to grab the rotor. I then stopped for the day to think it through.
Round #2:
When I was bleeding the brakes the previous day, I noticed that brake fluid wasn't squirting out the bleeders like I had seen in the past. This told me that there must still be air in the lines. So I decided to borrow a vacuum brake bleeder tool from a friend and see how that works. It bled the brake lines better than I ever expected, but I still had no brakes at all. At this point, all I could do was stare at the full master cylinder in awe as it mocked me into submission. I had no choice but to make the executive decision that either my master cylinder or prop-valve was not working. I called up a company that sold power disc brake kits and ordered a booster, new master cylinder, and new proportioning valve.
About a week later I tried my luck again. I installed the new master cylinder, brake booster, prop valve (all while spilling brake fluid down my painted firewall and onto my newly painted frame). For those of you that don't know, brake fluid strips paint and leaves the metal oily so it is difficult to paint the 2nd time. Moving on....The brakes are now bled for the 100th time, and as you may guess, no brakes! Disc brakes can be so Exciting, so much better than those great working consistant drum brakes I had. I then called everybody that knows anything about anything asking for ideas.
Round #4:
Time passed along with frustration, and I gave the old disc brakes another go. I made sure that the front and rear brake lines weren't swapped coming out of the master cylinder, and they were correct as I suspected. I had also heard rumors of the importance of working rear drum brakes. The rear drums grab first when you hit your brakes, so if they don't grab, your front braking ability could possibly be compromised. Sure enough, my new rear drums were adjusted and looked like they should be working. As frustration was begining to build again, I decided to take off the front brake calipers and put blocks of wood in between the brake pads to see if I could get a firm brake pedal. DING DING, I finally had the firm brake pedal that I wanted. The bad news is, the car won't stop if you have blocks of wood in your calipers in place of rotors, no matter how good the brake pedal feels. I reattached the calipers hoping for a miracle, but there were no miracles in my cards that day. Still no brakes.
Round #5
I knew the problem had to do with the front calipers, but I had no idea why. I stared at them for hours, took them off dozens of times trying different things, and everytime I reinstalled them, the brake pressure was mysteriously gone again. Suddenly, it all started coming together. I took off the calipers, and measured the distance between the upper caliper mount hole and the rotor. Then measured the lower caliper mount hole to the rotor. There was about a 1/4 of an inch difference that I couldn't see with the caliper bolted on. The sliders on the calipers compensated for this difference when they were bolted on, tricking my eyes to think the calipers were straight. Sure enough the caliper bracket was made incorrectly on both sides and the calipers were sitting crooked on the rotor. This meant that when the brake pedal was pushed down, the calipers twisted the bracket and straightened themselves out on the rotor. By the time all of this compressing and twisting was done, there was no pedal left to start grabbing the rotor. Once the brake pedal was released, the calipers twisted back to their happy position and the caliper pistons pushed in about 3/8 - 1/2 inch farther than they should have.
Round # 6
The problem was finally found. I took the brackets off, made new ones like a should have in the first place, and bolted it all back together. I finally had the brakes that I wanted. It only took twice as much money and 15 times as much time as I had originally hoped.
-HRCS