Decreasing the radius of a fender
If you want to decrease the radius of a fender designed for 700c wheels to fit 650B (or even 26"), start at one end of the fender and gently apply forces in the direction of the arrows. Basically you want to pull the fender edges out with your index and middle fingers, while pushing on the center of the fender with your thumbs. Don't apply so much force that you cause a visible change in shape, it's all about feel. As soon as you feel the metal giving, stop. Then work your way inch by inch along the entire length of the fender. You may want to wear gloves, as it may hurt your fingers!
After you've gone over the entire length of fender, mock fit it over your wheel with inflated tire and check for an acceptable fender line. Repeat the process in the opposite direction if you haven't reshaped it enough in the first pass. It's all about many tiny adjustments over the length of the fender that have a cumulative effect. If you've reshaped it too far and the radius is now too small, you can undo it by following the complementary technique described in the next photo.
Decreasing the radius of a fender
If you want to decrease the radius of a fender designed for 700c wheels to fit 650B (or even 26"), start at one end of the fender and gently apply forces in the direction of the arrows. Basically you want to pull the fender edges out with your index and middle fingers, while pushing on the center of the fender with your thumbs. Don't apply so much force that you cause a visible change in shape, it's all about feel. As soon as you feel the metal giving, stop. Then work your way inch by inch along the entire length of the fender. You may want to wear gloves, as it may hurt your fingers!
After you've gone over the entire length of fender, mock fit it over your wheel with inflated tire and check for an acceptable fender line. Repeat the process in the opposite direction if you haven't reshaped it enough in the first pass. It's all about many tiny adjustments over the length of the fender that have a cumulative effect. If you've reshaped it too far and the radius is now too small, you can undo it by following the complementary technique described in the next photo.