Disc brakes not stopping like they should

[68charger440R/T]

Hey guys i recently did a disc brake swap on my 68 charger, i used the ssbc kit #-A156 and it just ain't stopping like disc brakes should. if I'm driving about 20mph and slam on the brakes with both feet it just slowly coasts to a stop, shouldn't these babies lock up? Ive bleed them 3 times already with no difference in stopping power. The only thing i can think of is that i didn't bench bleed the new MC or its a bad booster.
It stopped alot better the first day i tested them and i could lock up the rear drums but now they wont with the proportioning valve wide open.
Any ideas?

Thanks, Jeff

[ChargerST]

I'm going through the same problem although it's not a SSBC kit. I have a hard pedal (so no air in the lines) but the car won't lock up the brakes. Actually the braking is way worse then with the drum brakes. I might have to add that I didn't use the provided bracket for the booster but made my own instead.
Made me thinking why I don't get enough pressure on the lines.
The pedal ratio on B-bodies is about 6:1 according to my measurements. Power cars use a special linkage that reduces the applied brake force and reduces brake pedal travel (that's why the brake pedal on power brake cars sits lower than on manual cars).

I'll have to do a few calculations but I think that the new booster and the reduced brake force due to the linkage are not enough for the new master cylinder (1") - that's why many people switched to smaller master cylinders (7/8" or 3/4"). But I was thinking about a different approach which is a) cheaper and b) easier to do: modify the brake linkage on power brake cars. Just drill another hole in the linkage and move the bell crank higher up (closer to the booster rod).

Check this site for calculations: http://www.deanoshiro.com/brakes/brakearticle.html

[68charger440R/T]

So where do i drill this hole, do you have any pics?

[ChargerST]

Haven't done any calculations yet but you could try to eyeball it. Check this thread first: http://www.dodgecharger.com/forum/index.php/topic,40597.0.html

If you move the bell crank up you will have more brake force - if the bell crank and the brake rod would have the same attachment point on the linkage you would retain the 6:1 pedal ratio without any reduction.

[dodge freak]

I'm not sure if this will help but my back drum brakes used to go out but pedal was firm, bleeding the back drums didn't work, only way was to crack the bleeder screws open and let it drip for 15-30 mins. Then they work again...for a few weeks.

Ended up replacing both wheel cylinders and problem solved.

But I would try cracking the front bleeder screws and just let them bleed for awhile and tighten the bleeder screws up and see if any improvement. Be sure there is no kinks in the steel brake lines. Old rubber hoses sometimes collapse inside but don't leak. I had a hard brake pedal once but weak brakes and new rubber hoses solved it.  

[ChargerST]

Yeah, check your rubber lines! If you have air in the lines would result in a soft pedal not a hard pedal!

[Cooter]

Did you first "seat" the pad and rotors, or simply bolt on and go slamming on the brakes? I've never gotten a FACTORY set up to lock under "Controlled" circumstances, but I haven't been in a panick situation yet either. They never lock when you are trying to get 'em to lock up.

[ChargerST]

Did you first "seat" the pad and rotors, or simply bolt on and go slamming on the brakes? I've never gotten a FACTORY set up to lock under "Controlled" circumstances, but I haven't been in a panick situation yet either. They never lock when you are trying to get 'em to lock up.

Even with unseated pads and rotors the stopping power should be greater (at least in my situation - I have a hard time stopping my car when going down the driveway with 3mph...).

[resq302]

Almost sounds like you have a bad power brake booster.

[ChargerST]

Almost sounds like you have a bad power brake booster.

hmm, I started the car with the brake pedal pressed - when the engine was running the pedal moved down a bit so I figured the booster is working. But I realized that I might have screwed up because I put a T piece in the vacuum line that goes from the manifold to the booster. The T piece was intended to provide the vacuum for the canister for the dash controls (the new check valveonly has one outlet).
Started a thread about this here:  http://www.dodgecharger.com/forum/index.php/topic,77835.0.html

[68charger440R/T]

Do you guys think a bad booster or lack of vacume could cause this cause i did put a new engine in and the cam seems a bit lopy

[resq302]

Do you guys think a bad booster or lack of vacume could cause this cause i did put a new engine in and the cam seems a bit lopy

Absolutely.  You need a minimum of I think 14" of vacuum for power assisted brakes to work properly other wise it would be like trying to stop a car with manual disc brakes.

By giving it a more radical cam, you decrease the amount of vacuum.

[ChargerST]

Yeah, check your vacuum! I worked on the car today and bolted the booster back in but left the vacuum canister disconnected and now the car stops way better (but still room to improve). I also modified my linkage but it didn't work with short bell crank (pedal would hit the floor) - a longer bell crank would solve that problem - maybe I'll fabricate one and see what happens.

[bobs66440]

Just a thought, I had a similar problem. The car wouldn't lock up the brakes or stop worth a damn until they got really hot. Everything checked out so I purchased some very expensive cold pads with no change. Then I went to AutoZone and bought the $18.00 el-cheapo pads and BAM! Instant lock-up!