I've used a ball peen hammer to crimp (dent) the chainstay, properly backed by a half round block (finished frame, chainring clearance). Worked but not satisfying from a craft perspective. Then I made some dies that I drove with a vise, also backed with a half round block, on chainstays not yet brazed into the frame; used those for tire clearance. They work great and you can easily have multiple dies but the setup procedure is a tad fiddly. Repeatability is difficult. I made this today. I'm not the first. It's really sweet. Setup, alignment, repeatability and controllability are fantastic. This one is for chainring clearance but I'll build a larger one for tire clearance. If it works half as well as this one it will be a raving success. Shoulda done it years ago.

image.jpg

image.jpg