I have ridden in T shirt jeans and trainers many times, admittedly that was in the 70's when it was acceptable and we were all just a bit crazy (well alright a lot crazy). I have had gravel rash more times than I care to remember and yes it hurts. I wouldn't ride anywhere now without full leathers, gloves and boots, I have always worn a helmet, even in the 70's we weren't that stupid.