How much clearance do you need from your tire to your fender? Where is the tire goibg to expand the most? I have about 1/4" room between side of my tire and fender

 

As a wheel spins at speed it grows in diameter, doesn't get any wider. I have about the same clearance as you do, on my rear tyre!

 

I assumed you meant side clearance, if you mean between the tread and fender, at the largest diameter of the tyre, you may just have enough clearance, as long as there are nuts or bolt heads in the way!