Datsun Roadster Forum-311s.org

Datsunparts.comInc wrote: Mon Aug 16, 2021 5:11 pm 1st Nissan had 2 different parts numbers for these drums. There was never a supersession of one to the other nor was there a Service file about how to make one work in place for the other.
When I had the Roadster drums and the Z car drums made 8 years ago we created a drawing that overlapped the specific dimensions of each of the drums that noted the difference between the two and then the manufacturer created a aluminum blank that could be used to make both parts with simple machining processes to achieve correct direct replacements without compromise. Kill two birds with one stone.
Roadster drums have a machined area that is recessed in the center inside the drum. The roadsters rear axle flange indexes inside of this recess thus the axle stays center on center with the drum. The holes in the drum are drilled for 7/16" x 20tpi studs.
On the Z car blank they left the recess out as the Z car drum never had a recess and the axles therefore center on the 12mm metric axle studs.
That is why when people installed the Z car drums on a roadster they would end up off center as there is no recess for centering and since the holes in the drum for the Z car are for the larger metric studs they had to eye ball centering the drum on the 7/16 studs and then torque the lug nuts down so the drum would not move off center, a difficult task indeed and one I would not do.
Often people drove up to my shop with a pulsing brake pedal when depressed, which was the clue that the drum was off center as the rear shoes when applied would move in and out of contact with the steel insert friction surface as if the drum was out of round.
Honestly, I don' think many even checked. The drums looked kind of the same so even though the part number was different ...oh well give it a try.
I suppose small sleeves could be made and put over the smaller 7/16" x 20tpi studs in the area where the drum would make contact in the larger hole and then hold center, but without the recess in the drum, the drum still sits out too far for my liking.
That is why WE always replicate the correct parts and spend a lot of time doing so which is not everyone's thing.

Out of 300 there are only 7 left https://www.datsunparts.com/2549 Using these later drums on a early car requires bending the small lip back on the back plate to provide clearance for the finned portion of the aluminum drum.

Dean

Gregs672000 wrote: Tue Aug 17, 2021 10:44 am Truly, the wealth of knowledge from this group is just awesome. None of the above applied to me (RX7 rear diff, etc on my car) but it amazes me the knowledge that can be shared... thanks to all.