norcalz28

iTrader: (13)

So today I am driving around, and I tap the brakes a little aggressively but not pedal to the floor or anything and the brakes just lock. They make no attempt to stop the car, they just lock. I already have my c4's I just need to swap them in, but my question is , is this common with the delco/morraine setup? I have rebuilt calipers, drilled/slotted rotors and earls ss lines up there, as well as a new master. Why won't they stop any better? Are they really this ****ing ****ty????

Will

89 Iroc Z

Well you're among the lucky few that the stock brakes actually work. I can not lock my front unless it's wet. That's on a new master cylinder, brake booster, rotors, and pads. If you don't want to lock them do threshold braking. My guess is there probably nothing wrong but if there is something wrong my guess is that your proportioning valve may be wrong (if you have done a rear brake conversion in the past) giving to much bias to the front. Since you have an 89 you have the better PBR rears (if you have 4 wheel disc option) which should stop you fine compared the pre 89 cars.

On another note I am frustrated with the 89 PBR rears and switching to LS1 rear when I go home for summer break. Which C4 setup are you going to run HD or non-HD?

norcalz28

iTrader: (13)

I do not like the 89 rears much either. They use very little of the already meager braking surface surface available, and mine are completely rebuild, new pads, rotors, earls lines, and they still will not hold the wheels from spinning in Nuetral if I jack up the rear. I am going to be using an adjustable prop valve as I am beyond fed up with this crap. Someone should sue GM for this disgregard for safety.

As for the c4's I am going with the non-hd setup. I figure thats big enough for me and I am not sinking anymore money into this heap.

Will

slowTA

iTrader: (1)

Old tires? I'm running some old calipers and master cylinder along with a good set of pads and standard rotors... the car stops fine. More rear brake will help with the front lock some, but if they're locking to fast I would change the pads to something with a different compound.

DuronClocker

iTrader: (1)

Buy new tires. The last few days I've actually been able to lock up the tires a few times...which has surprised me. Now I don't WANT to lock them up all the time, I'd just like to know they work. I figure a good braking system should be ABLE TO lock the brakes, but it shouldn't happen if you're a good driver. My car has been able to a few times lately, but not all the time, so I'm not quite sure why sometimes my braking is good and sometimes its not. I don't have ceramic pads, but it almost seems like they act like ceramics.

George

Just by way of an additional comment, I have a 1983 J65 set up with cheap pads and, in warm weather on dry pavement, it will lock up the KDW 275/40/17s that I have on the front if I want it too. I have to really stand on it with the J65 MC and all but it will lock up.

norcalz28

iTrader: (13)

My whole beef with the system is that it starts to feel like its working and you give it a little more pedal too quick and it just locks. I have driven a ton of other cars and they all seem to bite and really plant the car when the brakes are applied forcefully. And even some non-abs cars. My front brakes just plain suck. I hope I never have to make a panic stop, because it would be over. I can't wait to get my C4's on there. And for what its worth I have ecsts 712's with maybe 10k miles on them, they still have a ton of tread left.

Will

Chickenman35

What are you running for pads? Some pads have terrible modulation. Did you change pads recently? Did they work OK before?

Are you sure that the rear brakes are working properly? Put the car up on Jackstands and apply brake and throttle to check rear brake application. Proportioning valve may be defective. If rear brakes are not doing theitr fair share then all the braking will be done by the fronts and this will cause premature locking.

If the above checks out, inspect the rotors to make sure that no contaniments like grease or oil have gotten on the disks. Careless appilications of Tire cleaners or Wax ( IE: Hand Sprays or Pressure Wash ) " might" cause this problem as well.

slowTA

iTrader: (1)

Mine actually feel the same way... they start working pretty good then nothing but lockup. I'm running the Kuhmos with HP+ pads, but I'm pretty sure my rear brakes don't do squat (J65). I'm going to upgrade the rear brakes over the summer and cross my fingers! Also, I've noticed the Kuhmos like to have some heat in them before they start working really well

Chickenman35

HP+ pads....are those Hawks by any chance? If so... a very grabby pad in my experiences. I'm found Bendix Titanium pads to be an excellant pad for Street\Autocross use. Great stopping hot or cold and excellant modulation. Very liniar in brake retardation.

For the rear brakes, an adjustable proportioning valve will work wonders.

slowTA

iTrader: (1)

Yep Hawks, they're pretty powerful pads and they are easier to use than Performance Friction. The rear upgrade should balance the car out nicely.

Chickenman35

That's what I thought. Rear upgrade should help...but I definately would never use Hawks in the rears for street use. Way, way too grabby IMHO.

Have never like the feel of Hawk's on the street. Good retardation when hot ...but very poor modulation. Some of the compounds are very Rotor unfriendly. Same with Porterfields.

I like to use a lot of rear brake bias, as I trail brake and use the technique to rotate the car. This requires a rear pad with a very smooth and liniar retardation curve. Hawks just too " on " and "off" for my taste.

norcalz28

iTrader: (13)

I am running some napa gold pads up front, guess its time for a change. As fr the rears, the pedal will not stop the drive wheels. The e-brake will hold it, but the pedal will not. I guess I need to do some tweaking.

Will

Chickenman35

Yep. First off I would ditch the stock PV and put in a WilWood ( or adjustable unit ).

https://www.thirdgen.org/newdesign/tech/propvalve.shtml

Then I would think about changing pads. As I mentioned....you can't go wrong with Bendix Titanium. Dean likes Stillen, but they might be hard to find locally.

If you have Delco Morrainne rear calipers ( Iron Calipers ) you can get the Titaniums for the rear as well. For PBR brakes the rears will have to be the Bendix " Premium " pad. No Titanium coating for "break-in" but the Bendix PBR rears are a danged fine pad. "FF" rating ( which is the top material rating short of Race pads ) and they are suitable for the occasional track day, although they are intended as a High Performance street pad.

Souseless

If the e brake will hold but not the pedal then the problem is not the rear brakes themselves, but the hydraulic system. It could be that a good bleeding will help. Also look for a pinched line under the car. The e brake proves that the calipers are good. You need to find out why there is no hydraulic pressure. If you are not the original owner someone may have done this on purpose so that they could burn up the rear tires easier.

Good luck

norcalz28

iTrader: (13)

Interesting theory. I always suspected a pinched line, I had this on my 86 before. I will take a look. Would a a faulty prop valve also cause this kind of condition? I have a new one, but I am stuck on what to do because some people are telling me to gut it and use it as a distribution block for the lines so I can install the adjustable unit. Then others say just install it as is and try it out. I guess I will start checking this week. Thanks fellas

Will