I have a 99 Pontiac grand am, 4 cyclinder engine with anti-lock breaks.
I have noticed a vibration or shaking when I hit my breaks. The vibration seems to happen when I am at about 30 mph to 40 mph. When I am below 30 mph the vibration/shaking goes away.
I have had new tires put on the front since with an alignment. I have also had the brakes changed and are about 4 months or so old. I just had a friend last night look at the brakes and he says they are good. I don't know what else could be causing the vibration/shaking.
What about the rotors?
how hard are you braking to get this sensation? ABS gives a significant feeback through the pedal that would feel like shuddering brakes.
It probably is just your abs. My bmw does the same thing when you hit the breaks too hard. Because if it was anything else, it'd be a constant sensation and not just at certain speeds.