My bike takes a hammering in the winter because of the snow/ice/grit here in Norway. So I want to swap the all-welded-together Shimano Nexave chainrings for something which will allow me to just replace the middle chainring when it wears out.
I don't want to change the crank, or crank arms, if possible.
Can anyone suggest which Shimano chainring set would be compatible to replace the Nexave? The chainrings (picture attached) are 22-32-42. The crank is square tapered (picture attached - note that I screwed the cap bolt back on for safekeeping after removing the crankarm).
I note that the spider does not have threads on the backside to screw the inner chainring to, which is why the middle chainring is so bulky. I have been unable to find any chainrings which look like my one here...
It's a Cannondale MTB from 1999.