Nelson started to coach racing cyclists in 1953 and was the Great Britain team masseur on national and international events, including the Olympic Games, Commonwealth Games, seven World Cycling Championships, 21 Tours of Britain, three Peace Races (Warsaw-Berlin-Prague)and two Tour of Bohemia. He has helped numerous teams during 41 Manx Weeks and 32 Girvan Internationals.
In the 1960s, among the riders he coached were individual time trialists Keith Stacey (British Best All-Rounder 1965) and Eric Matthews (24-hour champion 1968). He also coached the Seamons CC time trial team.
In the 1970s and 1980s, he coached road racing cyclists including Alan Kemp, Ian Binder, Brian Pownall and Mike and Jeff Williams. His most successful riders were Paul Sherwen and John Herety. Sherwen rode the Tour de France seven times, finishing five times; he and Herety both won the British National Road Race Championship. Brian Cookson, president of British Cyling, is also an ex-rider.
His methods, based on care of the body, power training and monitoring the heart rate, helped Hamish Haynes (British National Road Race Champion 2006) who joined the training programme as a third-category rider: under Nelson's guidance, he became an elite rider within two years before turning professional for a Belgian team.
One feature of Nelson's home has, for decades, been the nightly venue for riders from schoolboys to experienced seniors, from national champions to those seeking to improve moderate standards. The youngest rider he took on is Craig Lyons, then 7. He refuses to coach riders over 40.
He was awarded the British Empire Medal for services to cycling.