musicars

This summer I converted the front drum brakes to disc brakes on our '72 Cutlass using a kit. I've been going nuts trying to figure out issues I'm having. When I first start it up, apply the brakes, and put it in gear, I have to hammer the brakes to the floor to get it it to hold in place. I have around 3" - 4" of brake peddle travel. If I drive around for a while and hammer the brakes a few times, they sort of start to work and almost feel normal. but then a few minutes later I pull up to stop and I'm back to pushing hard to the floor to the point I'm not sure it will stop. My driveway is on a hill so if I pull up to back in I can barely hold it in place without creeping downhill.

So far I have done the following:
Bleed it a million times, swapped the master, swapped the proportioning valve, checked the push rod length, tested the booster, checked the back brakes, swore a lot, and bleed it some more.

Then today I noticed the following when I took off the front tire to look for anything funky:
The wear pattern from the outboard pad, on the passenger side, only showed towards the outer half of the rotor. As you got closer to the center of the rotor there was less wear.
So then I looked at the inboard pad and saw that it was only touching the outer edge of the rotor. With the pedal pushed down there was barely any contact of the rotor.

I think this would explain the issues but I'm not sure what is happening here. I had problems with the caliper brackets not really fitting well and rubbing on the SSIIs so I had to grind off the corners but not in a load bearing area. I had a feeling that I had gotten a bad set of brackets. They seemed bent. The calipers look a little tipped out on top. But I would think if the inboard pad hits on top the outboard pad would hit more on the bottom. Instead it appears to be hitting more on top on both sides.

Have not checked the drivers side yet.

Has anybody heard of this issue before? Not sure if I have bent brackets or goofy calipers.

Thanks for taking the time to look at this.

Highwayman

Do you want to hear something crazy? Awhile back there was two different guys that redid their disk brakes and couldn't get a solid pedal. Come to find out they had put the left caliper on the right side and the right one on the left. I didn't know you could even do that. Anyway, it put the bleeder screws on the bottom side of the pistons instead of the top side and they couldn't get all of the air to bleed out. They swapped the calipers side to side and everything worked out fine.

musicars

Good guess. Not many know about that. Not that crazy. I've heard of that happening. I think I read one of the previous posts where that happened. I was aware of that possibility when I put it together. I was actually a little paranoid of that so I left them in the boxes marked right and left up to the point I put them in. My bleeders are on top.

Of course, now I'm going to go look at it again! Does sound like something I would do.

I'm pretty sure it has something to do with that caliper not hitting straight on the rotor.

Thanks!

Highwayman

Well, it sounded like a heck of an idea to throw out last night.

Is there anyway that the brackets could have been swapped side to side?

Do the brackets have part numbers stamped on them where you could check to see if you got the correct parts in your kit to begin with?

It just seems to me that if things don't line up right that you have parts installed wrong or the wrong parts were sent with the kit. But I guess you already figured that much out.

musicars

I don't think you can switch brackets left to right but I'll look at that. Tomorrow I'm calling the company that sold me the kit to ask them if this issue sounds familiar. I still think I got mutant parts. Things do not fit together as well as the factory parts.

I have a set of original GM brackets that I'm going to sandblast and paint. I'm going to get those ready just in case and maybe swap them out. Ironically, I had originally planned on using the disc brakes I took off a '72 parts car. I figured the kit would be faster and more cost effective by the time I got rebuilt calipers, cleaned everything up, and had rotors turned, etc. Boy was I wrong.

What makes it worse is the fact a friend used the same kit on his '69 convert and had no issues.

musicars

I hate it when the solutions to problems don't get posted so here is were my brake issue has gone:

I replaced the right side caliper bracket and the caliper still does not sit as square as I want it. I'm not sure if the caliper is a little off or the spindle is off were it mounts to the bracket. The GM bracket fits a lot better than the aftermarket bracket, but something is still off.

Everyone I talked to and the sources I checked with on the internet said the symptoms were not a booster issue and the booster passed the tests I did. Even though there should be the sound of the vacuum venting when you apply the brakes, the vacuum sound that was coming from the booster just seemed like too much. So, I took off the new reproduction booster and put on the 40 year old crusty original booster from the drum brake setup. Unbelievable, but now I have brakes. There must be something internally messed up that was not allowing the rod to push out all the way.

I now have a weird groaning from the front end when I release the brakes while turning a corner. It happens after I drive around and warm up the brakes. It comes and goes. I think, maybe the pads are making a noise as they release. They had gotten glazed during this process and I block sanded the glaze off rather than replace the pads and just glaze another set.

We want to drive this down to the Quad States meet this weekend so I hope nothing is too screwed up after all this.