Originally Posted by Rodan
This may seem really dumb but for a roller coaster 8 from same place, how do you know which bearings?
It will depend on which size hubs are installed.
If you remove a wheel you should be able to see the make and size cast on the hub somewhere....or measure the diameter and depth.
Possible options, if they are Knott brakes, are likely to be:
203*40 (this is what is on my 3.5)
If you can work out the hub then this page shows you the bearings used, however, better pricing can be achieved than shown here elsewhere:
If you can leave it all dismantled then the bearings themselves will have the part number on them for definitive identification.