SSCX Only!

Whoa. Quick and comprehensive. Thanks very much!

You make a good point Tom. I hadn't considered that.
While I'm not that precious over parts, and they were second hand to begin with, I suppose it could be a shame to ruin them.

I guess new cranks would give me wider choice over chainrings too..

Something like 42x18 is fine for dry courses, like it is now, but if you're riding through thick, gloomy mud then you're likely to need a smaller gear, so that wider choice on chainrings is useful.