Ford Mondeo problem. when I brake the wheels shudder as if the ABS was working?

[Wal]

For a while now it has been happening when I apply the brakes the front end shudders as if the ABS was kicking in but as I am braking normally then it should not, I have new discs and brake pads fitted about a year ago so that should be OK and it started just after I fitted new tyres but I have changed the wheels and tyres and its still the same, any ideas