Disc brake conversion ???? - Off-Road Forums & Discussion Groups

DanStew · #1 08-03-2002, 02:11 PM

OK... I might have gotten my leaks all cleaned up. I got some new copper washers that are a little smaller on the inner diameter and I did ad a little aircraft hose fitting sealant on the washers. I bolted everything up and it is looking good. I finally got the little brass fitting out of the Master cylinder and there was no spring or ball in the master cylinder. So I buttoned that back up. Only thing i have to do next is bleed the brakes. I have a question about how tight the pads should be on the rotor. When i first assembled the calipers on the rotors, the rotors turned with a little rubbing against the pads. it could be turned freely. After I pumped the brakes yesterday the pads are tigtly on the rotor and i can barely turn them both. Since there is no residual valve will the pads release from the rotor when i drive the jeep? or will they stay that tight on the rotor? I dont want to chance warping the rotors if they wont release from the rotor. I see that the piston is pushed out and pushing the pad against the rotor. Is this normal? Is there something worng?

Thanks

Hurcules · #2 08-03-2002, 05:01 PM

All the conversions I have done had tight pads at first. You have to shave off a few thousands of an inch of the pads to get it right. Your MC push rod might be a tad bit long too, there should be no pressure on the MC with the pedal at rest. Just bleed it and drive it, you will know if the pads are too tight before you warp a rotor, you will not get more than .5 mile away before they lockup.

DanStew · #3 08-03-2002, 05:19 PM

Do I really have to shave off the pads a little? When I first installed the pads on the calipers and everything spun pretty good. The caliper piston was in its seal and everything aligned real good. It only became real tight when I pumped the the pedals. The master cylinder is for a 1974 cj, and the pedals are from a 74 CJ, so I thought they would be matched for each other. I still have to bleed them, and my lovely wife said she would be willing to step on the pedal to help me bleed the brakes. It must be loe!! [img]images/icons/blush.gif[/img]
I will do a test drive and tell you how it went.
Thanks

DanStew · #4 08-03-2002, 06:59 PM

OK. I bled the brakes and took her for a test drive. I now have no breaks. Pedal goes all the way to the floor and nothing. I will rebleed the brakes again. I think I have air in the rubber hoses still, because they are looped pward. Is there anything else to do to get pressure there? I can tell there is some pressure, because the brake rotors are clean now, but that could also be from the pads rubbing a little. Also the jeep doesnt lock up because the pads are tight, so i believe i dont have to grind anything down. So my next step is to bleed some more. Is it a pain to get the calipers to bleed all the air out?
Thanks

Hurcules · #5 08-03-2002, 08:16 PM

Not it is not a pain to get all the air out, I have 4 wheel discs with the same GM calipers, and they bleed very easy. You do have the calipers on the correct side right? Bleeder screws point up on about the highest point on the caliper, not down. Your sealant on the washers needs to go, if there is a leak it needs to be fixed correctly. No brakes at all? No rear brakes? Why are your brake lines looped? Make them go into an "S" shape and retain the extra hose with a light spring going to the frame. The Jeep will lockup or refuse to move when the brakes warm up if your pads are a problem, like I said you will know. my Jeep did that because I modified my power brake MC to work with manual brakes and after .5 mile the Jeep would not move in low range 1st gear! I cracked the brake line to relive the pressure and drive back home.

DanStew · #6 08-03-2002, 11:02 PM

Hurc,
I have the calipers on correctly. bleeder to the sky. The lines arnt looped, but more or less in an upside down "U" It shouldnt be a problem. The back brakes arent working right now, it is something i knew about for a while now, something is clogging the lines, i tried to bleed them and no fluid came out. I will swap them out in a week or so for my old 11 inch brakes, or i might just do the disc in the back. I drove around the neighborhood "VERY Slowly" for a while, and that should have gotten them warmed up enough to see if they locked up, but they seemed kosher. I am going to bleed them some more. I am thinking i do have air in the MC now because it did go dry, but i never touched the pedals when it was dry, but i think air might have gotten into them. So i will get a big bottle of fluid and go at it again tomorrow. Unless somehow my master cylinder just died, there is probably air in the hose. Unless the one problem may be i didnt put back in that brass fitting when i went to take out the residual valve. Does that fitting do anything? I have a brass adapter screwed into the outlet, then the hose into the brass fitting, so it is not needed to really seal the hose, but i didn't know if it is there for any other purpose other than sealing the brake line.

Hurcules · #7 08-04-2002, 12:35 AM

Re-bleed the master, then re-bleed the brakes. No rear brakes? That is an accident waiting to happen..... I don't know anything about residual valves, I have always had either 4 wheel drums or 4 wheel discs, and never messed with the valve in anything else. I do know a couple of racers that use residual valves (2 pound) with disc brakes though.