Challenger brake problem

My friend has a 71 Challenger 412/340, 727 with Gear Vendors . He recently upgraded the front disc brakes to use the 2nd gen Viper 4 piston aluminum calipers while keeping the 11.75 Cordoba rotors. To do this, he installed the correct 70 B-body drum brake knuckles and the caliper adapter brackets from AR Engineering. Everything fit together fine. He had a later model 2 bolt aluminum master cylinder with the remaining brake lines and proportioning valve that came on the car. Braking was fair, but no better than with the single piston calipers. The WIERD thing is that while braking in a turn, the brake pedal would push back toward his foot! He changed to a different M/C with the same symptom still there. I told him to check the wheel bearings. He did, and the nut was loose by 2 1/2 turns on one side and about 3/4 on the other. A test session afterwards showed no change. The brake hoses are not binding. He added a Wilwood adjustable prop valve since he knew it was a good idea, not in an effort to cure this problem. With the current setup, it stops better than before, but the pulsating upward from the pedal during turns still has us confused. Okay now, any clues?

No April fools' right . I'd jack up the front/remove the wheels and have a helper play w the pedal as something has to be loose/excessive play that's causing the pistons to be pushed back during the lateral movement in the turns. Start w the bearings

We found the problem! Isn't it a pisser when you THINK that you have all the right stuff and somehow it still doesn't work?
The B body drum knuckles he had were to blame. The inner wheel bearing to knuckle clearance was excessive. We checked a 73 Dart 10 inch drum knuckle and the bearing fit great. Who knows why the B knuckle was wrong. He tried another with similar results. With it all back together, the wierd problem was corrected. WAAAhhhhoooo!

'73-'76 A-body drum knuckles have a larger inner bearing diameter than ('72 and older) B/E body drum knuckles. '73 and newer rotors will not fit the early knuckles without my spindle bushing kit.

You are the man... Want to run for president? You would surely be better than what we have now!