On Friday, November 23, 2018 at 2:11:49 PM UTC-8, Earls61 wrote:
Do you have horizontal dropouts? Maybe try positioning the axle differently. Some other suggestions:
Verify correct chain length, verify top der pulley does not rub on bottom of cassette, check B screw adjustment, verify der hangar is aligned with hangar alignment tool. Good luck!!

Earl, I forgot the idler pulley problems. Joerg has a 40 tooth humongous low gear and you're probably correct that his derailleur probably doesn't have enough take-up to shift into low gear and not push the top idler pulley into the cogs.