After truing the rear wheel and sharpening the brakes, it managed those hazardous steep gravelly descents safely eariler today. The back wheel skidded straight, my heavy trailer didn't jacknife. Perhaps Black Jacks will afford more grip. I would much rather stick with durable and (so far) puncture free Marathon Plus, if at all possible, and keep using this bike for towing. Why take two bikes into the shower? I'm ordering Black Jacks.