You are reading a single comment by @M_V and its replies.
Click here to read the full conversation.
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
@M_V
Actually possibly figured it out myself.
61708 aka 6708 = 40mm x 50mm x 6mm wide
61808 aka 6808 = 40mm x 52mm x 7mm wide
Seems to make sense that both bearings would have the same internal diameter as the freewheel centre is universal. Also figures that the bearing for the larger outer rings would have a larger outer diameter. The width less obvious but I guess if the actual balls are bigger in the 61808/6808 it makes sense.
Bearing codes quoted in the OP are quite different to those that tie in with the WI codes and different to each other too so I presume they are wrong.