Brake drum and rear hub spacing ?

Hi all , I've replaced the cush drive rubbers on my 73 commando . I understand that it's a tight fit but after assembling the rear wheel I see a 1/8th -3/16 gap between the drum and the hub .
After disassembly I see that the rubbers sit proud of the hub , Is this normal ? I don't think it should be metal on metal but is there an acceptable gap ? or should the drum touch the hub ?

Thanks , Dave

Mine has a gap - maybe not quite 3/16" but not far off.

01dlx said:

Hi all , I've replaced the cush drive rubbers on my 73 commando . I understand that it's a tight fit but after assembling the rear wheel I see a 1/8th -3/16 gap between the drum and the hub .
After disassembly I see that the rubbers sit proud of the hub , Is this normal ? I don't think it should be metal on metal but is there an acceptable gap ? or should the drum touch the hub ?

Thanks , Dave

Click to expand...

Sounds normal to me. The cush does not set the gap - dummy axle, bearing, bearing spacer, hub bearings set it.

Thanks guys

What measurement or test is used to determine the number of bearing spacer(s) (item 06.7603) are needed? How do you measure and satisfy the requirement - is this simply to keep the rotating drum bits from scraping the drum brake "floor" with its rivets? Hope this makes sense - have found little information on this topic, especially in our workshop manuals.

Jdub said:

What measurement or test is used to determine the number of bearing spacer(s) (item 06.7603) are needed? How do you measure and satisfy the requirement - is this simply to keep the rotating drum bits from scraping the drum brake "floor" with its rivets? Hope this makes sense - have found little information on this topic, especially in our workshop manuals.

Click to expand...

There are no "bearing spacers" in the rear wheel other than the top hat one that is pushed into the brake drum bearing. Between the brake hub and brake backing plate there is usually a thin spacer to keep the backing plate from rubbing on the drum - nothing to do with rivets. Actually, I always include one but AFAIK, it's officially zero or one - number 21 (06.7603) here: https://andover-norton.co.uk/en/shop-drawing/75/rear-wheel-drum-bearings Note that the drawing is a little misleading - it goes on the other side of the drum and it is not a bearing spacer.

Thank you Greg, I do see that the shim (7603) sits against the bearing spacer dummy axle (see Greg post next) and I posted on this in this thread about that subject. I am just trying to understand why the part is listed as "Check Required Quantity" which indicates a variable number (if any) and how you would measure that. I think you simply add them if you sense the drum is rubbing internally - fortunately that is not the situation in my case.

Jdub said:

Thank you Greg, I do see that the shim (7603) sits against the bearing spacer and I posted on this in this thread about that subject. I am just trying to understand why the part is listed as "Check Required Quantity" which indicates a variable number (if any) and how you would measure that. I think you simply add them if you sense the drum is rubbing internally - fortunately that is not the situation in my case.

Click to expand...

It doesn't sit against the bearing spacer. It is installed between the brake drum and brake backing plate. It touches no bearing or bearing spacer. If the brake blacking plate is bent it will not fix it - you must straighten or replace it. Often the brake drum will contact the brake backing plate somewhere in its rotation. I've almost always found a need for one to stop that touching and never have needed more than one. Adding more would make the rear wheel assembly wider and even more difficult to get between the ends of the swingarm.