Having had my concerns about 4566 colour suitable satisfied, I / we / you now have another problem, dodgy wheels!
Two of mine (BR) and a fellow club members gwr 45xx were not at all smooth in running. The problem seems to be either the quartering being off or what we think was the culprit, off centre driving (centre set) wheels. The effect gives a "thump-thump" sound when running, worse on corners than straights and at very slow speeds on the worst example it made the loco stall. The effect was very noticeable when pulling a 3 coach train as the coaches just jerked along behind the loco, looked very poor. Any one else had the same problem? We exchanged the locos today in our local model shop, however this turned up another 5 dodgy ones before we found 3 suitable ones, not a good sign for Bachmann's quality control!