My question relates to oil leaks. I’ve noticed a few small oil leaks and I’m not sure if this is normal for these hubs. The other thing to mention is that the hub is second hand/pre owned and I have no idea about the service history.
The first leak, which I’ve only noticed once, is the between the “disc flange” and the hub shell. It was a small amount, maybe a few MLs I guess. It doesn’t seem to have re-occurred. I’ve also noticed quite a bit of oil when I take the external gear mount/ reaction arm off. I’m using the Monkey Bone post mount adaptor so had to have this section on and off a few times to get it correctly setup.
I know I can get a gasket for the disc flange/hub shell but should I simply carry out a normal oil service/replacement and monitor it for a while whilst in service OR should I do something before pushing it in service?
I don't know anything about the reaction stay's mounting, but find it odd that it should in any way be connected to the internal lubrication of the Rohloff hub. However, and I give this without looking it up so others can correct me if necessary, Rohloff hubs have a breather hole on the axle, and it is normal for a certain amount of oil to escape via this. An overfilled hub might therefore show oil when you remove a torque stay, depending on where it is fixed to the hub.
On overfilling the hub: you may read on the net, and in Rohloff instructions, that you should fill the hub with 25ml of all-seasons oil. That's a cover-the-manufacturer's-ass instruction. 15ml fills it and the rest will be lost.
Rohloff hubs are not "sealed" in the same way the gearbox on your car is sealed. To save weight, there are, for instance, paper gaskets, and the gearbox "sweats" oil. In the days when I filled my gearbox with 25ml as per the manual, I often had a puddle under the bike, mostly clear because it would happen more often on warm days soon after a service. My wheels get wiped down once or twice a year (I ride on tarmac almost all the time), and the sweat-oil builds up a very thin layer of most clean oil in that time if the hub is filled right, but enough oil to attract dirt if the hub is overfilled.
About the other apparent "leak", I think you need to observe it again and for a good period before you start disassembling anything to replace gaskets. For a start, is any oil coming out around the plug on the feedhole and being flung to the flanges by centrifugal action? That small plug is supposed to be locked with Loctite, which probably also acts as a seal; if you reuse it without cleaning and re-Loctiting it, the seal can be less than perfect. Until I learned about putting in only 15ml of oil, my hub required wiping inside the flanges every once in a while, with no source of the leak obviously visible, and definitely not the seals, which were new, and I always use a new plug with Loctite applied at the factory. Even so, it was by elimination the cause of the overfill leaking.
So I suggest you wait and watch for a bit. Clean the wheel, change the oil in the hub according to the factory manual, which you can download on the net, but put in only 15ml of all-season oil. That ensures that, even if you lose all the liquid oil in the hub (very little actually) through a real leak or by normal sweating, the gears are still properly coated and cannot be damaged by use. Now you can ride and check for the source of the oil. If there is no oil, or only very little from the normal, expected sources, then you're good to go.
I think, considering that the hub is second-hand and you don't know what the previous owner did or did not do, you're right to approach the matter carefully. In general, a Rohloff hub is not as clean as for instance a Shimano HGB (I too have both) and nowhere near as clean as a sealed-for-life hub like the SON hub dynamo that posters here also have. But most would hardly notice, because they clean their bikes more often than I do and because Rohloff oil, especially when most likely to be flung out in larger quantities near a service, is pretty clean stuff, easily mistaken for water.
In general, I take the view that a bit of oil on a Rohloff box does no harm; it may even be the positive sign of a recent service!
Good luck.
