The BSA Workshop > Twins

A65 Thunderbolt 1972 Front Conical Hub Front Spindle 37-3796--Carry over

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Arthur: thanks for your pictures. Please can you tell me the length of your spindle and the thickness of your distance piece? I have dismantled my spindle assembly. My bearings are the sealed type which are not the open race type that you can pack with grease as shown in the BSA W/S Manual! It was assembled with all the grease shields which, are they needed? Also is the sealed bearing type thicker (wider) than the open type? Did BSA fit these in their final production runs and if they did? Was the spindle modified to suit?

Thanks again to you both!


The rubber shielded bearings have the same dimensions as the unshielded type and are often fitted as replacements because they keep the grease in and the grit out. The bearing was a common part for the earlier full width hubs as well as the conical.

They should measure 20 mm inside diameter x 47 mm outside diameter x 14 mm wide. Probably marked with a bearing number - an SKF would have markings 6204 2RSH for the sealed type.

Only leave out the grease retainers if they do not act as bearing spacer.

Thanks Julian, I have been down to my local bearing dist. They confirmed what you have said, the key number is '6204'. This number is  recognized by all the key quality manufacturers. They also checked out the Hoffmann 120 number, as in the BSA W/S Manual, this refers straight back to RHP 6204, who bought out Hoffmann.
So the only query that I now have is my Spindle? Is there only one type? Do the smaller bikes with Conical Hubs have a different spindle? OR is there only one type?


Looks like only one type of spindle for all the conical hubs 6 inch or 8 inch BSA or Triumph, single twin or triple.


My hub is fitted with sealed bearings and I left out any inner grease retainers. I know my spindle is the same part number as you quoted previously but I'll go and measure it's length for you shortly. It sounds as though the RH projection of your spindle is not the same as on mine?

Unfortunately, I don't have an accurate method of measuring the length of the spindle now that the hub is assembled. However, the spindle projects 1 11/16" from the outside face of the brake plate nut and projects 1 15/16" from the grease retainer on the LH side of the hub. What are your corresponding measurements?


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