My 2 cents.
Sir its perfectly fine. I am sure you know how ABS works. and I dont want to sound like I-KNOW-IT-All......but forgive me for creating a stage to adress the issue at hand.....an ABS kicks in when the sensors on wheels sense a lock.
And what would happen when a wheel locks, it slides on the road during that milli second period. The system is supposed to break the wheel jam. and it does by dis-engaging and re-engaging the brakes.
But since you feel a constant vibration on the foot, its because when the system re-engages, it again senses a wheel lock/jam and again disengages the brakes.
So we agree to the point that our car's wheels lock several times during ABS function. and therefore the wheels skid/ spin again skid/ spin several times during all that period.
Since we have established the above thought, the minor screech you hear is perfectly normal.
And now for the part that why do you hear sometimes and why not always. Its because you drive on different road types during your course of everyday journey. Also the road temperature is different at different times of the day. When hot, you wheels are bound to produce a louder screech when skidding on the road. Ever noticed that on a car without ABS, when you brake hard on a road covered partially with dirt, there is no sound at all !!! Likewise, during ABS, the tyres may screech or may not.
I would agree 100% with Mr. Hash4u. If it aint broke, dont fix it. Try to steer while hard braking, if you dont slide during that period, everything is perfectly Normal.
Cheers!!
