IMO they are too big, and will stick out too much. 275mm = 10.826 inches. So they should stick out almost an inch and a half on each side.
245mm = 9.64 inches, which means about 3/4" will stick out on each side.
I don't know enough about tires to tell you if this is bad or not. My guess is the sidewall will be more vulnerable to cracks/dry rot/other damage with a 275. How much more? No idea.
I will say wider means more traction, which is always good.
Scott