I've never, ever flatted my knobby MTB tires and they're 1.95". I have flatted my 1.25" Forte Slick City tires 3 times in about 600 miles. I have flatted 700x25 Bonti selects 6 times in 3,000+ miles. When I switched to the Bonti hard case tires on my road bike, all my flat tire woes faded away.