I need an expression to be a simile to gripping the wheel of a car tightly.
Try; Hold on for dear life; 'He grasped the wheel and hung on for dear life' or 'He held onto the wheel as if his life depended on it.'
'He held the wheel like a vice'
'He was gripping the wheel so tightly his knuckles shone white'
'He gripped the wheel so tightly, they would have to pry his fingers off with a crowbar'
Hope this helps.