Last year I asked the question if anyone else had experienced problems with derailing of the current Hornby carriage bogie but the onlyresponses were to tidy up my track. At that time it was the pullman range and I eventually sold them on. I now have acquired a new SR MK1 brake / 3rd which is doing exactly the same thing. I have measured the max wheel bearing width (inside one flange to the outside edge of the opposite wheel. This come out at 17mm for a b-b of 14.3mm. Using exclusively peco track I find the actual gauge on curves to be 17.2mm. This of course explain why the wheel sets manage to fall between the rails. Now the pertinent Q? Do these wheels move easily on the axles and what b-b would be appropriate?