BSA Owners' Club Workshop Discussions

The BSA Workshop => Twins => Topic started by: Tjwood on 14 Feb, 2026, 14:44

Title: A65 QD hub bearing seems to have play in it
Post by: Tjwood on 14 Feb, 2026, 14:44
Hi. I am rebuilding a 1970 Thunderbolt. The QD rear wheel is built as per the parts list diagram but when everything is bolted up tight in the swing arm it is possible to tilt the wheel slightly side to side by about 1mm when the wheel is gripped at opposite sides and it is pulled/pushed. It feels like the 'wobble' you'd get with a badly worn bearing but I've put in a brand new FAG bearing (C3 clearance I think). It looks like it's the free play/clearance within the bearing that is causing the problem as the inner race is locked tight on the spindle and the outer race is firm in the hub. Does anyone have any advice on how I can sort this out please?
Thanks
Tony
Title: Re: A65 QD hub bearing seems to have play in it
Post by: Ian C on 14 Feb, 2026, 16:29
The C3 clearance 'may' be the problem. I've always used (and I'm sure BSA specified same) CN clearance bearings for wheel hubs. You would typically require C3 for inside an engine or possibly gearbox due to the higher temperature environments. HTH