I am using both 406 and 451. For 451 available tires are usually slicks. Heavier treaded ones are rare and even if available, it's 1.35 inch. I got Schwalbe Duranos and I think Kimbell Jaya still has a few of them. GW cycle have them. Most common are Kendas likebthosebused in most brands as original. You have more choices in Singapore though , even Continental and Vedrestein.