All of 'em can be slightly different, but with fenders my bike has very little clearance running 700c tires that actually measure 29-30. That's a total of 682mm, which less the 630 (27") = 26mm or maybe you fit a 1 1/8". Yours may be "looser".

I don't recall which wheel was tighter - often it's the front, but for some reason I'm thinking rear on mine. Not sure. I could change out the fender mounting hardware for something a little more clearance friendly, too, but it fit the tires I had.