I have 27" x 1 1/4" tires on my Mondia and I checked them with a pair of calipers and they measured 1.390" or 35mm. This is with 80lbs. They are Michelin Pro Tech that I got at REI and they were under $30 each. They are mounted on 1 1/4" wide rims. I am glad the bike has extra clearance to clear the wide tires , even though I have to mount the rear wheel with the tire deflated. The ride is great , but they are heavy. I am running them at 75 lbs and I weigh 155.