This is uber geeky, but the velcro can take some practise to use skillfully. It works well with jeans because the actual hem of the pant cuff is fat and stays below the velcro, but with light material with a simple hem, sometimes the pants pull up through the strap. Also you have to apply the velcro very low, near the ankle bones, because if it's higher up the calf, the leg is wider, and if it then slips down a bit it becomes too loose. But if it's too low it pulls the pants too tight and interferes with the top of the pedal stroke. I put my foot up on a curb to pull the pant cuff up slightly, then apply the strap as low as I can.