In 1951, Coleman secured a works contract with the British manufacturer, Associated Motorcycles, who produced AJS, and Matchless machines. He rode an AJS to eighth place in the Isle of Man Junior TT, while his Norton failed to finish the Senior TT.[5] In the 1951 Grand Prix season, he finished 12th in the final 350 class standings.[6]
In 1952 he came fourth in the Senior TT, and third in the Junior TT, riding AJS in both events.[5] He was fourth in the 1952 500 class standings.
For 1953 there was a fourth in the Senior TT, and while leading the Junior TT, his bike broke down and failed to finish.[5] For the 1953 season, he was tenth in the 500 class and sixth in the 350 class.[6]
In 1954 he won the Junior, the first New Zealander to win a TT.[5] In the 1954 Grand Prix motorcycle racing season, Coleman came twelfth in the 500 class, and third in the 350 class.[6] This was also the year Associated Motorcycles quit racing. He won the 500cc in Hedemora TT in 1954.
Coleman met and married an English woman, Jacqueline Etherington, and they returned to Whanganui where he ran a thriving motorcycle and car business.[7] He provided financial support for many New Zealand motorcycle racers including; three-times World Champion Hugh Anderson, Keith Turner, Dave and Neville Hiscock, Andrew Stroud, Robert Holden and Dennis Ireland, as well as American rider Pat Hennen and Belgian rider, Gaston Rahier.[7]
In the 2001 New Year Honours, Coleman was appointed a Member of the New Zealand Order of Merit, for services to motorcycling.[8] He died in Whanganui on 6 August 2019.[9]