of coz the best is to change 23mm but 17 mm is also enough already.... there is not too big dfference between them but only the choice of 23mm is more.... actually the wheels of most of the RTR monster trucks are also 17mm only.... like revo3.3 5309 and e-maxx 3908 .... if it is broken then you can change it to 23mm if not you can still keep it as it is not important..