Shoe suggestions
 

Preface:

I have the Shimano R-131, which I bought a few years ago. I moved from some Nike shoes with nylon soles. Loved the switch and the shoes were very comfortable to start, but never really wore them for any more than a few hours (less than three, most typical).

I've recently (within the past 4 months) been getting back into the swing of things after a few years of mediocre riding. I've frequently been riding 3+ hours, a few time a week and I'm really having trouble with my shoes. Before the 2-2.5-hr period they feel fine, but then I start to get this excruciating pain on the undersides of my big toes (the knuckle-pad). It kills.

Question:

Any suggestions on which shoes I should look at first. I imagine it'll be as difficult as finding the right seat, but some proper direction would be nice since I haven't looked at shoes in a few years.

Two requirements, carbon sole (or at least as stiff as my R-131s) and Look-style cleat holes.

Thanks in advance.

Are you using the stock insoles? I had a similar issue to yours, and swapping the insoles out for Superfeet fixed the problem for me.