Foot/toe numbness when biking

I'm going to guess shoes are too small.  I use to have a pair that I felt where the right size and had the same issue.  Eventually got a bigger pair and the problem went away.  It could even be that the shoes are the right length but too narrow.

Spot on

I find my foot is loose at first but gets tighter as the ride wears on. I use R086 Shimano road shoes, yours are mtb shoes. I wonder if that makes a difference...

I would also suspect shoe, but it can also be the location of the cleat.  That did make a difference for me in the beginning.

another vote for too tight, I get this sometimes and when I do, take my socks off and it's goes.

Yes, your shoes could be too tight, too small, or cleat position is wrong.  Always buy shoes with your thickest socks and late in the day.  And try them on in a crouch position, since that's how you'll use them (not standing up).   If it's too late for this, perhaps very thin socks? 

For cleat position, a fitter can help you place them correctly. 

Agree with the above on "shoe not fitting you right". I like specialized for this reason...they feel the best on my feet, without socks. I could wear them forever and never have any pain/numbing, etc. They also have this special feature that spreads your toes out, which helps in this area.

Many thanks to all for the advice. Much appreciated. Will make changes after my next tri at the end of this month. I think I will need to find another bike shop as they suggested when I bought the shoes (my first pair) that they should be snug....hmmm. Thanks again