Britain's Neil Fachie and Barney Storey won tandem gold with a world record after mechanical failure hit teammates Anthony Kappes and Craig MacLean.
Fachie and Storey, the husband of Paralympic champion Sarah Storey, set a blistering pace in the blind and visually impaired 1km time-trial.
Defending champion Kappes and MacLean were the last pair to go but twice failed to complete their opening lap. Officials allowed one restart but ruled them out after the second failure.
Fachie, who is partially sighted and competed in athletics in Beijing in 2008, and pilot Storey clocked a world record of one minute 01.351 seconds. That took them past Spain's Jose Enrique Porto and Jose Antonio Villanueva, who finished with silver.