Mavic Superlights shudder

Hi, I have an older (2008) set of Mavic Kyserium Superlights. The wheels are in good shape. I get a shudder from front wheel when I brake on downhills. I have adjusted brakes, rebuilt the caliper and sanded the shoes. The rim is clean. I thought it was the shoes at first, catching. Now I wonder if the wheels spokes are moving under load (braking on turns downhill) and driving the rim into the brake shoes. I weigh 190. I might open up the gap on the shoes to rim a b it to see if that cures it. Any thoughts appreciated.