Skeetman

I am at my wits end with my brakes. I have converted my drum brakes with the CPP disk brake kit front and rear. I can not lock the brake up, the car does stop but can not skid. I have used both the CPP and Right Stuff master cylinders. Does anyone know of a mechanic or brake shop in the Downers Grove (Chicago Area) IL that could help me. I have been working on this problem over 2 years now. Any help would be appreciated.

droldsmorland

Year make and model are needed for us to accurately diagnose this. Sounds like you need to install an adjustable proportioning valve. A drum brake car more or less puts equal hydraulic force out to all 4 wheels via the distribution block mounted on the frame. A disc brake system needs front brake bias to work properly.

Skeetman

1967 Cutlass A Body. I have the correct master cylinder, first one was a CPP 1-1/8" dia with an adjustable prop valve second master cylinder 1" dia with fixed prop valve from Right Stuff and no changes same results.

droldsmorland

How did you bleed the system? Do you get a good stream out of each bleeder?

70W-32

Power or manual?

Gary M

Sorry, what is CPP?

droldsmorland

Classic Performance Parts

Gary M

Did not know they sold Oldsmobile parts.
They do have a trouble shooting page in the tech pages. Did you read that yet?

jozw30

Do the rears have e-brakes built in? If yes they may not be fully adjusted......

steverw

How fast will the car stop, enough to stop the car quickly in a panic situation? Just askin because technically a car should not skid, thus Anti Lock brakes were designed to eliminate skidding/locking up. So it could be that the car is stopping fine, but only you know that. The old drum brakes did lock up/skid which does not help the car to stop in a shorter distance.
Im assuming from your post that the brakes are not working well to stop the car safely, is the pedal mushy/soft?

junior supercar

Am I reading it right, the car stops but you want to lock the brakes up, skid and essentially go out of control?

joe_padavano

They sell A-body brake parts. Chevelle and Cutlass brakes are the same.

Skeetman

System is bleed properly and many times by pump and release also by pressure method.


Rear E-Brakes are set correctly


The car does not stop safe or quickly. The brakes work OK but not good. The car has power brakes 18/20 inches of vacuum with the vacuum canister I can get up to 24 inches.
The pedal is not soft seems normal for light stops but around half way down the pedal is hard and does not stop the car quickly. The pedal will go to the floor when bleeding so there is no interference with the linkage.

dalilama

D&M Corvette Services in Downers Grove on Ogden Ave just east of Finley works on lots of classic cars and probably would be the best to take your car to in the Downers Grove area. I've heard lots of good things about them (but I've never used them myself).

Fun71

I understand your meaning, as in maximum braking occurs when the tires are not skidding. Technically, though, with a properly functioning non-ABS system, the brakes should have enough clamping force to cause the tires to skid. It appears that in this case the brakes do not have sufficient clamping force.

edit:
What size tires do you have on the car? It is possible that large tires with a soft, sticky tread may have so much traction that the brake clamping force, even with properly functioning brakes, is not enough to cause the tires to skid.

Skeetman

Tire size was 215 X 75 X 14 and now I have 215 X 55 X17 and there is no difference in braking. I have also change the front brake pads and no difference. The pedal is hard and can not come to a fast or hard stop.

Fun71

You said the car has power brakes, so what booster does it have? Could possibly be an issue with the booster since you said the brake pedal is hard.

Skeetman

I have a new 11" booster. There are no vacuum leaks and it holds vacuum after the engine is shut off.
The complete brake system is new. The old drum brake distribution block is not used and replaced by line direct from the proportioning valve.

Fun71

New does not always mean good. I have had issues with new out of the box boosters and master cylinders.

coppercutlass

I had some brake issues recently. It came down to crappy new parts. Just for what its worth.

Rick P. Schultz

I would think that the proportioner valve is the issue. A good rule of thumb that I have found is a 70/30 front/rear.

Skeetman

My Cutlass will be going to D&M next week.
I have spoke with many mechanics about the problem and Tom at D&M knows about aftermarket brake systems which makes me comfortable taking to them.
I'll post the results then.

Skeetman

My brake problem has been resolved, it was a bad brake booster check valve. The typical problem with a check valve is it won't hold a vacuum and leak. My check valve would not allow vacuum to the booster. This valve was brand new from CPP which came with the new booster. I knew the problem could have been something minor I just could not find it. I went thru the brake system over and over. Tom at D&M had saw this issue once before. I am very happy with D&M in Downers Grove.
Thanks everyone for their responses.

joe_padavano

I have to say, that's a new one on me. Thanks for posting the resolution. It also again shows that "new" parts aren't always "good" parts.

oldcutlass

Makes sense... I'll have to check the 66 SS for the same issue as we checked everything else.