Originally Posted by DataJunkie

The tires will be fine.
Shoe fit is very important to get right and preferences vary person to person. This is the one item I always try on at local shops. I purchase them there as well since I find the idea of trying on something at a brick and mortar and then purchasing them online to be rude but that is neither here nor there.
I find it is more important to size the shoe to your foot such that the heel cup holds your heel snug and the toe box is just wide enough. Too much movement results in bad things like your foot sliding around and your toes impacting the front of your shoe creating black toenails. Some say to go up a half size. I opt for a well fitting shoe instead and feel more comfortable as a result. My cycling shoe size is exactly the same as my normal shoe size unless it is a winter shoe where I will increase up a full size to allow thicker socks.