I guess that you are talking abot 559 sized rims and not the old sized 26" rims.
Well, the 2.4 is the nearest size but measure the distance between the rear triangle to make sure that the 2.4 inch tyre will fit. I know the difference is only 0.05" but better safe than sorry.
The 2,2 tyre is better for some things though, so think on.