Below is some general info regarding wheel sizes which will work on our Giro 26 bikes beyond the original stock wheels. If wheel sizes are a mystery to you, we highly recommend learning a little more about wheel sizes before reading the article. You can find general wheel and tire information, here: http://www.sheldonbrown.com/tire_sizing.html,
GIRO 26 AND 26 ATT FRAMES: THE BASICS
Both the Giro 26 (steel frame) and Giro 26 ATT (aluminum frame) come stock with 26” (ISO 559mm) wheels and 1.25” tires. Rear dropout spacing is standard MTB 135mm. Frames and forks come with disc brake tabs and canti posts for V-brakes positioned for 26” (559mm) wheels. Both Giro26 frames also have a rear brake boss for a traditional road brake caliper which will work with 700c wheels. Also, the steel and alloy forks available on these models have enough clearance for a 700 wheel with 23c+ tires. All of this makes both bikes extremely versatile as far as wheel sizes go, but there are a few things you’ll need to keep in mind before making any changes.