Originally Posted by bulgie

Yeah calling that 4 positions is wishful thinking. The 812/A only does one thing (OK 2 if you include keeping dirt out); it sets the position of the cage-rotation stop screw 812/1A.

That screw doesn't come into play in normal use since it's just moving through air. Only at the extreme where it hits against the lower knuckle does it do anything. Yes, if you assemble it wrong, it hits too soon and robs you of some of the useful range of travel, but there's no reason to do that other than by accident. There's no upside or benefit to assembling it that way, so it's simply a mistake.

Easiest way to prove the stop screw 812/1A doesn't do anything in normal use is to remove it. The mech works perfectly, and it even removes the possibility of it reducing your useful range by hitting too soon.

The only downside to removing the screw is fast wheel changes. Without the screw, the cage over-rotates when you take the wheel out, so you have to grab the grimy cage with your hand and wind it up a little before putting the wheel in. That only adds maybe two or three seconds, which is nothing at all to the 100% of us who aren't getting a fast wheel change in a race. (yeah right, with a 50+ year old derailer on your bike? What kind of race are you in??) Carry a rag or alcohol wipe to get the chain grime off your hand and you're good to go.

Not that I seriously recommend removing it; I leave it on, on my bikes. But I make sure it isn't stopping my cage rotation too soon.

So, we're only left with the two choices of spring pre-load, which do affect the function, but only a little. In most cases either spring position will work. With a dual-spring mech like the Juy Simplex of the same era as the Record and NR, the balance between the strength of the two springs matters a lot. But with the NR, with no spring in the upper pivot, the parallelogram always stays at the same angle, doesn't float fore and aft, so the lower spring tension only affects the amount of sag in the lower run of the chain. It doesn't affect what size of freewheel you can use, at all. With a Simplex or any other mech with a "B-spring", it matters, but not with NR.

So my basic rule when assembling is: line up the two spring holes in the cage with the two in the 812/A spring cover, so the rotation-stop screw ends up in the right place. Then put the spring in whichever of those holes you want, it doesn't matter much.

If you want a wider gear range than a NR is comfortable with, you can fiddle with sliding the wheel back in horizontal dropouts, which helps, and then fine-tune the chain length to get it to go into all gears without crunching anything, but the limits are still pretty severe compared to most other brands/models of derailer. With a big freewheel (I've used up to 31t), the allowable range in front is quite narrow. If you'll allow the chain to hang slack in small/small then you can eke out a little more. If you'll allow large/large to actually break or bend things if you forget and shift into that gear, you can eke out still more, but obviously I'm not a fan of that "trick". You will forget one day and shift into the forbidden gear.

The #1 thing you can do to a NR to get a wider gear range is put a Rally cage on it. Totally easy and not even expensive, now that repro Rally cages are available from Merry Sales.


Mark B