rear disc brakes are dragging badly.

[Moose]

just installed wilwood 12.19 kit with 4 piston calipers, and wilwood new manual master cylinder.

the rear brakes are dragging almost like emergency brake is on. But I didnt get the cable from lokar yet, so emergency brake isnt hooked up.

If i let it cool, everything seemed fine. then drive for a few minutes, and it almost locks up.

[GetMore]

Do you still have a residual pressure valve installed?

[megaladon6]

X2
it sounds like you still have the combination valve for rear drums.

[Moose]

ok, ill ask the dumb question.. WHAT is that?

i honestly think the brakes are horrible pedal wise, firm pedal, but car still doesnt want to stop. I thought it was better stock then it is now.

[Moose]

Ok.. are we talking about block on the bottom of this pic? if so, yes thats what i used to split the lines.

https://static1.pt-content.com/images/pt/2009/04/69boost_side-1.jpg


since i cant use that, what do I use?? this has just been a nightmare!

[megaladon6]

simply, the residual valve (part of the combo valve) holds enough pressure in the lines to keep the brakes from fully retracting. this keeps the gap from the pad/shoe to the rotor/drum at a minimum and thus the pedal travel at a minimum. drum systems hold more pressure to overcome the return springs. IIRC disc systems either don't have one or it's a minimal pressure. either way you need a combination/proportioning valve. for a 4 disc system.

[GetMore]

You can buy a "T" fitting to split the front brake lines, and install an adjustable proportioning valve on the rear line.
Or, you can buy the SSBC distribution block/adjustable prop. valve/brake light switch piece. It's about $120, but it keeps everything a bit neater. (I don't know what use the brake light switch is, but haven't seen it without it.)

[ProdigyCustoms]

On a factory disc brake camaro, the residual vavle is located on the side of the subframe under the passemger seat. Look under the rocker an see it it is there.

However, many have run with this with no problem. That only holds 2PSI of pressure, probably not enough to creat a actual drag you could notice. Regardless it should go. You can get a 1/4" inverted flare union and elimnate that pretty easy.

What could be your problem , you may not have enough slack in the master cylinder push rod. If it is to tight, it may be holding pressure on the brakes all the time. You push the brake but the master does not fully release. Usually this is more noticable on the rear brakes.

Go under the dash and make sure there is free play in the pedal. Turn the adjustment rod in a couple truns for security sake.

[ProdigyCustoms]

Call me tomorrow if you need me.

[Moose]

Well I'll try the simple route first with trying the rod. if not I'll get the T fitting and do this next. That means 4th time bleeding the brakes..:banghead:

[Moose]

so now the front brakes are locking as well.. now im really confused. all ive done is adjust the rod to the master cylinder.

[strangler]

I retained the stock disc/drum distribution block when I re-plumbed my 68 A-body.... I will be running LS-1 rears...... After reading this am I correct to assume that I need to remove that block? Thanks guys.

[ProdigyCustoms]

No, his problem turned out to be all in the master cylinder. You should have no problem with the factory distribution block. But the residual valve under the drivers seat needs to go

[strangler]

Thank you Frank. I replaced the line running to the rears from the dist block and do not have any valve, so I guess I'll be all set. Thanks again!

[Moose]

Frank and a bunch of others finally got me on track with a different master cylinder. car stops great now!