Let's assume this is not cold induced numbness - that's what the OP has said.
I found that getting a good pair of insoles in stiff but not carbon road shoes (SPD-R cleats) made a big difference. Still get it a bit but much, much better (ie 600 over weekend). I bought '
Superfeet (yellow)'. I deliberately flex my forefoot as often as I think about it to minimise the adverse effect.
Could be too tight, but the OP would surely know that, and have tried someone else's on, or cycle with no socks (say after swimming).
Cleat position: Longitudinally needs to align with your natural 'fall of foot' on the pedals. Put the cleats on but with the bolts a bit loose and see what feels right. Then tighten them in that position (easier said than done). As far as how far forward/back the cleats should be, having read Steven Hogg's article
power-to-the-pedal-cleat-position, mine are as far back as they can go, and this seems particularly beneficial for triathlete types who are going to have to run straight after a hard ride.
What are triathlon shoes ?
Triathlon shoes normally describe road shoes that have velcro fastenings that 'go the wrong way' (and often only two straps but wide ones) so you can jump on the bike after the 'end of transition' line (the shoes are already clipped onto the pedals) and get some speed on before inserting feet (individually) and slapping over the straps (reaching down from the saddle). At the end of the cycle stage, reverse the process, straps off (and they fall to the outside and thus don't foul the cranks/chainring), feet out and on top of the shoes ready to dismount and run into transition.
