When I first got my car I converted it to SSBC power brakes and dual master cylinder (disc/drum). It has a proportioning valve and the front and rear brakes are to separate systems. I can't lock up the front or rear brakes at anytime and I don't feel like there is enough "stopping power". Would adjusting the proportioning valve change that? I haven't touched it yet, but everything else is brand new, the calipers, pads, rotors, M/C, booster, rubber lines, and some of the steel lines. The front brakes are distributed by what looks like a SSBC block and the rear has what looks like a Baer proportioning valve. This car does have the factory K-H disc brakes and rear drums.
btw I think the P.O painted the engine bay with all of the brake lines, distrubution block, and proportioning valve still in place lol.
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-Ryan 66 A code Coupe w/ C4
Day I bought it:
How it sits now:
RIP - 93 sonic blue foxbody
Adjust the proportioning valve untill the rear brakes lock up under a panic stop then back it off untill they do not. You do not want the brakes to lock up at all.
Is that the correct distribution block that should be used? Don't know for sure so wondering and Just asking.
Honestly I am not sure. I didn't change any of the P.O.'s plumbing I just changed lines. Also, the brake don't feel like they are grabbing as much as they should because I can never come to a complete stop (loose term) - as in it takes me stomping on the brakes to roll into a softer stop. That just doesn't seem right to me. I am used to the foxbody brakes and like the brake feel but, these seem like somethings wrong compared to everything I have driven.
__________________
-Ryan 66 A code Coupe w/ C4
Day I bought it:
How it sits now:
RIP - 93 sonic blue foxbody
Adjust the proportioning valve untill the rear brakes lock up under a panic stop then back it off untill they do not. You do not want the brakes to lock up at all.
I guess what I should ask is why is it so hard to come to a complete stop easily? I think it takes too much effort to come to a complete stop more than there should be. It seems like there is not enough brake pressure? I have 17" of vacuum and the line doesn't collapse. The booster is good. I was thinking the proportioning valve might be adjusted wrong.
__________________
-Ryan 66 A code Coupe w/ C4
Day I bought it:
How it sits now:
RIP - 93 sonic blue foxbody
I guess what I should ask is why is it so hard to come to a complete stop easily? I think it takes too much effort to come to a complete stop more than there should be. It seems like there is not enough brake pressure? I have 17" of vacuum and the line doesn't collapse. The booster is good. I was thinking the proportioning valve might be adjusted wrong.
Well, your first step is to adjust the valve and get as much pressure to the rear brakes as you can without them locking up. Also Make sure your rear shoes are adjusted up correctly. Check your power booster and Master cylinder and make sure it is the right set up for your car.
Adjusting the proportioning valve only affects the rear brakes. The front brakes always 'see' the full pressure created by the master cylinder. For example if the front lines see 1000psi line pressure under a certain amount of pedal force then the proportioning valve will cut the pressure to the rear lines to 700psi. Locking the fronts has nothing to do with how much the pressure to the rears is reduced.
Is your brake pedal spongy feeling or hard? Your MC may not have been bled correctly or you may even have the wrong MC. Could be alot of different things.
Adjusting the proportioning valve only affects the rear brakes. The front brakes always 'see' the full pressure created by the master cylinder. For example if the front lines see 1000psi line pressure under a certain amount of pedal force then the proportioning valve will cut the pressure to the rear lines to 700psi. Locking the fronts has nothing to do with how much the pressure to the rears is reduced.
Is your brake pedal spongy feeling or hard? Your MC may not have been bled correctly or you may even have the wrong MC. Could be alot of different things.
The pedal progressively gets harder if that makes any sense. It is kinda hard to explain. The first 1" -1 1/2" feels very light but the brakes do engage, the after that the pedal starts to get harder. I'm not able to compare to manual brakes as the car wasn't drive-able when I first bought it. I've bled brakes many times after replacing the calipers and lines. The MC was bench bled before I put it in. The brake system is the only thing that has given me problems with this car lol.
__________________
-Ryan 66 A code Coupe w/ C4
Day I bought it:
How it sits now:
RIP - 93 sonic blue foxbody
Could it be a vacuum issue? Booster? My car is sitting, but it had/has the same issue, I know I have a leak in the intake gasket in the back, so my vacuum is probably compromised. I also have a booster that is most likely in need of rebuilding.
Start with the engine off after the car has been sitting at least 1/2 hour. Take a tape measure with you. Depress the brake pedal as far as you can and hold it. Measure the distance from the bottom of the dash to the pedal pad and write it down. Let the pedal return and immediately depress it again...not fast or hard, but just like the first time. Do that about a half dozen times in a row without too much of a pause between pumps and on the last pump hold the pedal down and measure the distance again. It should be very close to what you recorded the first time, at least within 1/2". If it's not, then you still have air in the system that needs to be purged.
Let's assume that the pedal did not improve or you solved THAT problem and it still doesn't stop well. First question is.... "Are the rear brakes adjusted properly?". The shoes should just be dragging on the drums as you turn them by hand. If not, adjust, but before you do, pull the drums and make sure the shoes are installed correctly with the shorter primary shoe facing front and the larger secondary shoe facing the back.
Okay, all's well there but it still doesn't stop well? Pump the brakes and listen for the shoes traveling inside the drums...the squeaking of the springs as they travel in and out. If so, you may want to check the rear port of the master cylinder to see if there is, indeed, a residual valve, present. To check, you need to pull the flared seat and check for the valve underneath. To pull the seat hand thread a sheet metal screw, one that is large enough to only go in a couple turns, into the seat, then pull straight out with a pair of pliers.
Only a couple more things that I can think of. First are pads and shoes that have a very poor friction coefficient coupled with drums and rotors that have not been what I call "dressed". I typically run a sheet of emery cloth around the surface of new drums and rotors to take off that nice "shiny" from the machining. Next are shoes and pads that have not been properly "seasoned". After installation, new linings, especially pads, should be subjected to 3 hard stops from 25mph to 5mph allowing a couple minutes between each stop to cool, then 3 more from 50mph to 25mph, again allowing them to cool. Next thing I'd do is hop in and pump the brake pedal until all the vacuum is gone from the booster, hold your foot on the pedal and start the car. You should have the pedal drop at least an inch as the diaphragm in the booster is pulled toward the m/c. If not, sounds like booster issues. Also, if you still can not lock the brakes, you may want to make sure the pushrod between the booster and the m/c is traveling far enough to completely apply the brakes. Good luck.
I will be watching this thread with interest. I have the same problem with my SSBC disc brake conversion but I have manual brakes. I will have to check for my res. valve in the m/c.
Bart, you said to check the rear port for the valve. Does that mean it is in the front brake portion of the m/c? Sorry 66coupe for hijacking your thread.
I will be watching this thread with interest. I have the same problem with my SSBC disc brake conversion but I have manual brakes. I will have to check for my res. valve in the m/c.
Bart, you said to check the rear port for the valve. Does that mean it is in the front brake portion of the m/c? Sorry 66coupe for hijacking your thread.
Sorry for the confusion. No, the port for the rear brake system, which would physically be the front (small reservoir) on a disc/drum m/c. Thanks.
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Brakes won't lock? (front or rear)
