Knocking from front left hand wheel

[jampot]

I live on a common with small potholes, going over them causes a knock from said wheel, if I gently apply the foot brake the knocking stops, I have replaced roll bar bushes , well all the front bushes and joints after another knock drove me crazy and I lost my temper replacing all the front suspension, now its trying its luck again, I replaces the caliper pins Saturday but its still there, I have been around trucks and cars for 46 years so I know my way around, wonder if anyone has come across this before I replace both front calipers and caliper brackets , more expence .