I have 4 bikes with CR18's The bikes with Continentals I have a tough time with. Bikes with other brands have not been an issue. Make sure that the bead of the tire is in the deep part of the rim all the way around. Tires tend to try to push to the outside once one side wall is on the rim.

Plan to get that Tire lever/ Tire jack next time I see one. LBS doesnt stock it.