Oldsmobile/Buick Repair: 89 olds brakes, flex hoses, wheel speed

Question
89 toronado trofeo with ABS, reduced braking effectiveness. For
regular stopping, brakes work fine. Braking quickly as in a panic
stop or unexpected merge in front of me, and the brakes engage
only partially with substantially reduced braking effectiveness,
and the car pulls to the right, for less than 1 second, then the
brakes engage fully and the car stops normally. If I step very
lightly on the brake first for a second, then continue into a
"panic stop", no problem. I disconnected the ABS in the trunk,
and the reduced effectiveness on "panic stops" still occurrs, but
no pulling to the right. I have tried 3 normally competent
mechanics, no luck, no ideas.

Answer
Hello Ernie,
To me it sounds like there is a lot more travel in one wheel cylinder, or a restriction in a brake line.
The travel could be in the left rear wheel, causing the right rear to grab earlier. Could also be in the front, but since the front disc brakes don't have return springs, I doubt that would be the cause there.
However, if the brake flex hoses to the front wheels have a metal sleeve where they clamp to the front steering tower, I have seen them get restricted at that area to the point that fluid would almost not pass through, and actually, I have seen them to the point where it wouldn't pass through at all.
The easiest way to check that is to loosen the bleeder screw on one of them, and have someone hit the brakes one time, and watch how quickly the fluid squirts out, also observing the quantity. You could even use a little hose into a bottle.
Then top off the master cylinder, and test the other side.
Compare them a few times, and if the left is noticably slower than the right, the hose is where I would look.

There is also the possibility that the ABS is causing the pressure to one of the wheels to be reduced, which could be a valve in that system, or a wheel speed sensor, but that system is unfamiliar to me.

Van