To all : Good Morning !!! If using wheels with metal shafts , I like to make sure that the insulated wheels are all on the same side of the cars . I am not sure if it makes a difference on most cars made for DC and DCC , but I modified some Maerklin Cars made for AC operation and it made a difference there . Also since they were from their " Harry Potter " line I need to use 42 inch HO scale wheels . Thankfully they had NEM 362 couplers so converting to Knuckle Couplers ( Bachmann ) was easy . Cars worked well after that and were used on various engines . John2.