I wish someone would tell my brakes. Yesterday, on dry pavement, 65*F I had an emergency stop that caused the rear end to step out.

Current brake set up:
Reman MC from Autoparts Store
Fresh Fluid
*Bias Spring*
Reman Power Stop Front Calipers
Factory Rear Calipers
Power Stop Drilled/Slotted Rotors up front
Power Stop Pads in the Front
Factory Calipers in the rear, adjusted properly, cycle parking brake every time I shut the car off
Stillen Pads in the rear
Stainless Braided Lines (all 4)

Situation was driving up a country road around 55mph, "BUMP" sign on the other side of a hill and a section of pavement ripped out (about a 2" drop in pavement). So, I stand on the brakes pretty hard, and the rears lock up and start stepping out. Luckily I recognized what was happening, let up on the brake come and steered out of it. Scrubbed enough speed to not hit the dip in/out too hard... but that was a new occurrence in a thirdgen.

I wonder if I need better pads upfront or better tires?

 

The Iron caliper rear brakes (Delco Moraine) are the brakes that do not operate very well.

The Aluminum caliper rear brakes (PBR) operate very well...
and usually are a "night and day" difference in comparison to the Iron caliper brakes.

 

Yup, just like has always been said before, but apparently mine do enough to lock up the rears. Considering what you just said, does that mean I need a better pad upfront or better tires to prevent this?
I know a lot of folks are running the bias spring without this happening. So, unless I have the best Delco Moraine calipers in the world, something isn't right.

 

Do you know which Master-Cylinder and Prop-Valve are on your vehicle?

 

Prop valve is factory
MC is a a remand from O'Reilly's This one

Have to look back at a previous thread when I performed all the work. Had a bit of an issue getting every little bit of air out to get the pedal feel I wanted, and just can't due to firewall flex. I have been very happy with the street performance of the brakes since I overhauled the system. Had a bad brake hose causing a sharp initial pull and poor overall braking performance when I got the car, even found one front rotor a completely different dimension than the other - even by eye.

So, I ordered the power stop kit for the front, Stillen pads/rotors for the rear, and stainless lines all around (Factory Hard line on drivers side, but did get the axle hose). Also used a bias spring a friend had left over from upgrading his. The MC was't really an issue in hindsight, but at the time I didn't like the pedal feel and it had been 15 years since I pushed on a thirdgen. Same friend that gave me an extra spring had to demonstrate the firewall flex and douse my hopes of having a really firm pedal.

There is the history, and honestly, the brakes are awesome. I am sure they wouldn't hold up to track use, but for the street...nice straight stops, very little nose dive, and very positive pedal feel. I had performed some hard stops while bedding them in and just testing them out. This was the first time I had what I would honestly feel is an emergency stop. I thought I was going to lose my lower nose or air dam if I went over this void in the road too fast.

To be straight, the car does not lack for braking. I don't feel like it gives up a lot in street use to my other car, which is a C4 with J55 package. It needs brakes, so it is getting a similar upgrade with Slotted Rotors, CarboTech pads, stainless lines, new fluid, and bias spring this fall when the Rotors come in. Possibly I will feel differently then.

 

The system is unbalanced. Need to either up the front pads or reduce the bias spring in the combo valve. Not sure what the Power Stop front pads cost, but can try the same rating Stillen pads in the front that the rears have.

If that doesn't do enough then need to change the bias spring in the combo valve.

Note that a stickier front tire will make the issue worse. As they will be even harder to lock up prior to the rears locking. A stickier rear tire will help in balancing the system.

RBob.

 

The tires on my Iroc are getting up in age. I think 8-9 years so it is getting time. It would be stickier at all 4 corners. It is probably mis-matched pads and I am guessing with only a few 100 miles on them I could probably just change the pads out and bed them in for the fronts.