When I brake hard, my front fork sometimes vibrates. I think the front brakes are grabbing the rim hard, then losing contact, and doing this in an oscillatory manner which leads to the chatter on my front fork. Has anyone else experienced this? Is it because my brakes (shimano cantilevers pairs with 105 levers) are set up improperly? Does anyone have any insight on how I can eliminate or minimize this behaviour? The bike is a 2005 Bianchi Axis if that is relevant.