The Krosscyclos are listed as 27x1 3/8, and you'd expect them to be wider or at least have the same cross-section as 650a tires, but neither is true. I've had two sets that were no wider than standard 27x1 1/4", but were noticeably taller. So much so that I needed to mount the rear wheel with the tires deflated to clear the chainstay bridge. They should fit your 27" application, as long as you do the deflate-to-mount/unmount routine.

They're a great bargain suggestion, especially at Niagara's price.