I bought a new bike (Specialized Sequoia) for commuting to work. I added a rack and I already had an Arkel Bug pannier. I'm having a little bit of a problem with my heel hitting the pannier. I have it moved back as far as possible on the rack. It's not bad, but it happens periodically. If I get shorter cranks would this solve the problem? How do I know how much shorter (I have 175 mm cranks) for now. Any other suggestions? Thanks in advance for your help.