We use a wide 700c tire that runs right against the clearance of standard fenders. It can be tricky finding the exact adjustment where the wheel clears the fender but is certainly possible.
To adjust the fender, use a Philips screwdriver to slightly back out the screw on the back fender stay holder (fender stay acorns). It can then be slid up or down along the edge of the fender. Once you have found the point that allows consistent fender clearance, turn the screw until it locks into place. You can also remove the fender stay acorn from the edge of the fender once you unscrew it. You can also pull the fender stay strut off the fender stay acorn, without any risk of damage.