just put a new snow tire on my bike and it just BARELY fits. the sides of the tire are mildy rubbing the inner sides of the chainstays. the studs are not rubbing at all just the rubber. its enough that the tire spins a little slower when i spin it freely and when i ride it feels fine.
I've seen quite a few trashed frames over the years due to rear tire rub. Check to see if your axle is seated properly in the drop outs. Also, if it's only rubbing on one side you might need to get your wheel re-dished. Or your tire is too wide in which case trim the tire or buy ones that are narrow enough for your frame.
You should check to make sure that your axle is seated properly in the dropouts (although this usually results in seat stay rub not chain stay). Also if the tire is seated properly but only rubbing intermittently on one side the tire may not be seated properly or you might need to true your wheel. If the tire is rubbing consistently but only on one side you may need to have your wheel re-dished. If none of these are the case and it is rubbing on both sides it's just too damn wide and you should trim the tire and probably not buy ones that wide again for that bike unless your into spending quality time with your tire and a sharp knife.
thanks for the responses. it seems the tires are just plain too big for the frame. i was only planning on using these for snow days which is pretty rare, but i guess i will try just using the front and see if that works. these are literally the smallest studded tires in production, if only i had a couple more millimeters of clearance!!