8 To mount the fender on his frame’s new upper cross member, Tyler fish-mouthed a 1-inch-long section of 1-inch O.D. rod stock, then drilled and tapped it for 3/8 inch-16 hardware. A leather washer will protect the paint on the finished bike. Tyler chose a spun steel fender by Gas Box in Cleveland. This rugged fender is tailored to fit an Avon MKII Safety Mileage 18x4.00-inch tire. Knowing these specs in advance of ordering a custom-made fender is critical for buying the correct radius.