Nylon roller DIY limits
On a door with nylon rollers and standard spring tension, a careful homeowner can do one or two rollers on the bottom panel without much risk. The trouble starts higher up. Rollers near the top panel sit close to the cable drum and the torsion spring, and the track up there is often bent slightly from years of use on doors built in the 1980s or 90s, which describes most of the stock around here.