I was riding around at night and ended up plowing into the sandy beach at 15mph on my 80's Miyata road bike. And immediately afterwards, I get this weird grinding/crunching sound. Even after I cleaned up the sand, I still get this cruching sound ONLY when I'm pedalling "harder" at low speed. I'm wondering if it's because sand has gotten into the bottom bracket or the residues on the chain that is making the noise. I sprayed some brake cleaner and WD-40 to try to clean the BB out without taking it apart. what is the most likely cause of this noise? What should I do?