Note also that not everyone's 28 mm tire is the same width. Sometimes, tires rated as large as 32 mm are no more than 28 mm wide when inflated. What is so critical about 27 mm width?fmbp said:ARGH! I went into 3, yes 3, different shops yesterday to purchase one 700x27 or 700x28 tire. I came out empty handed each time! Are tires this width that uncommon? Two of the shops were smaller, more unique shops, and the third was a big box chain type bike shop.