Is it possible to change a Shimano FC131 crankset's chainrings? I'm going to buy a bike wtih this crank, but I want to change the bigger ring. This is one of the lower end shimano cranks -- so I am worrying that the chainrings may not be replaceable. 

Thanks

Guys now I'll be needing a DIY way to change the rings cuz those gears are wayyyyyy to low for me. I need something, what about pulling off the bolts or something?.....
No, you can't. 

The lowest Shimano level crankset with replacable chainrings is in the Acera group.

In any case, most replacement chainrings cost about as much as a Tourney (or even Acera) crankset, so it doesn't make much sense to replace the chainrings on those anyway.  

As mentioned in the answer to your other question, theres a very good chance your bike won't be able to clear a 48t ring if it was originally spec'd with a 42t ring.