FBinNY 

Unfortunately, there are some rims and tires that are harder to mount than others. If you combine a hard to mount rim with tight tire you have a nightmare.

I personally have a rule, no tire or rim is worth fighting over, and tires have to be easy enough to mount on the road on a cold, dark, rainy night, with sore half numb hands. I consider this critical because Murphy's Law holds and that's when I'll be changing a flat.

To understand your problem consider that the tire diameter has to be smaller than that of the rim flange. No tire would be mountable except that you can offset it to one side to get some slack (think of 2 stacked coins with one moved over slightly). the amount you can move the tire and get slack depends on the depth of the rim at the center, which is the key to the issue. Some rims do not have very deep centers, and tire mounting on these will always be a pain, but it shouldn't be impossible.


1- make sure the partly inflated tune is shoved well up into the tire, and then only inflated enough not to be flat.
2- finish mounting at the valve, because the stem's width will keep the tire out of the center where the rim is deepest.
3- start early working tire slack toward the end because that's when you'll need it. You can equalize the tire when finished.
4- when (if) finished push the valve into the tire to push the tube up with it, then pull it back down to seat it correctly.

Even doing everything right, a poor combination can still make it difficult. I've stopped on the road to help stranded riders whose tires were so tight that I could barely remove them with steel tire levers, whereas my tires can be pulled with my bare hands, or worst case started with a key or coin. If these tires are that tight ask the shop, or the cycling community to suggest tires known to be easier to mount.

Unfortunately the rim's contribution to the problem is too expensive to fix, and that will need to wait until your next wheels.