2001 anti lock brakes Q

I'm not sure why, but my van seems to skid when i make a hard stop and hit a bump or pothole at the same time. If there in any snow on the road i'm sliding and that makes for a long winter. Had the breaks done all around in the spring, told mechanic about the problem and he thought it might be related to back end issue. The back end does sit lower than the front didn't get the air shocks like he wanted. I do plan on getting winter tires this year and maybe upgrading the rotors. Any other tips to help improve breaking....
thanks in advance...:smile:

Make sure you are using the proper sized tires. Anything with a different circumference will effect how the ABS works...