I use a 1 3/16in. socket to remove the backing plate nut on the DLS brakes. Before getting this socket, I had resorted to a sharp tap on the edge of one of the flats of the nut with a punch & hammer, and this usually loosened it off, but of course this will mark the nut (not a concern if it's already butchered).
A 30MM deep well impact in 1/2 drive works if you grind or turn a bit off the O.D. These are available cheap at good auto stores. I just did a set of sealed bearings on one of these wheels while popping out the old bearings a inter dust shield got buggered not a problem I just left it out not needed right. Well as it turns out you now can tighten that nut to the point that it distorts the brake plate be for warned.
norbsa 1960 TR6 1963 Super Rocket 1965 650 Star 1966 441 1968 Thunderbolt 1969 Twinkle 250 1972 Fastback 1974 Roadster 1970 S.S Way too many BSA's not named http://decentcycles.com
what i used was a 3/4 inch drive socket (i think 1 1/4" AF from memory) but easy to measure. and a 3/4 to 1/2 inch adaptor to use a power bar i had in 1/2 inch. The 3/4 drive socket was deep enough to clear the axel as the axel would actualy fit into the square hole of the socket drive. I was easily able to get enough of the adaptor into the hole to undo it.
BUT!! how the hell are you supposed to hold the assembly tight enough to do it up adaquatley again???? I resorted to holding the other end of the axel in some soft jaws in a solid vice BUT i still dont recon i got it tight enough..
"There's the way it ought to be and there's the way it is" (Sgt Barnes)
You probably got it tight enough, if not be aware that at idle the plate can rattle back and forward and contact between the plate and torque lug on the RHS fork slider causes a noise that sounds like engine damage. That big alloy plate is like a gong and makes noise.
I used a Craftsman deep socket, 1.25 inch dia. I believe the round axle fit in the square hole (at last!) of the socket, with some room left for the tip of the ratchet. You can use a fork leg as a clamp for the axle. I don't remember it requiring a high torque.