2000 XJ with ZJ discs not responding

As title says, not that long ago installed ZJ discs with almost all new parts.

Once said and done I ONLY change the spring in my prop. valve.

I can barely lock up my back wheels on snow covered ground... me thinks they're not responding as they should be?

I've read that I could have changed the plunger/end cap for the prop valve too, would that have made a difference? There was a noticable difference between the springs...

Was there a special prop valve bleeding method I missed or something? I just bled all 4 wheels like you normally would when it was done.

"barely" meaning only on ice.

Something is way wrong there obviously. I didn't change the spring in my prop valve, but I did remove the "o-ring" which increased the rear braking power. I actually have a bit to much rear brake right now, but I'm going to see how it is once I freshen up the front brakes.

You might want to go back and check the prop valve and also make sure that your rear calipers are properly bled. You have the calipers oriented with the bleeders at the top, correct?