LinusR wrote:Brucey wrote:- with the wheel set so that the axle is horizontal, and holding the freehub body in your left hand, spin the wheel for a couple of minutes
Can I ask why hold it so the axle is horizontal? Why not vertical (or diagonal) with the freehub body uppermost so that the oil runs downwards?
The oil is centrifuged outwards and dragged round by the turning parts and should soon work its way into the freewheel mechanism. If you tip the axle very far past horizontal the oil may drain into the hubshell via the hollow bolt instead. Once tipped away from horizontal, any oil that hasn't yet made it's way around the outside of the RH hub bearing cup is unlikely to do so now, no matter how long you spend twirling the wheel round.
BTW because you are holding the freehub body in your left hand, you can feel any changes in the state of the bearings/pawls as the oil penetrates. The RH ballrace in the freehub body may be full of dried grease and this will at frist inhibit penetration of any lubricant.
Because the seal is still in the RH end of the freehub body, even with the axle removed, you can have a puddle of oil at least 5mm deep in the space that is ordinarily occupied by the 1/4" hub bearings. This is deep enough to penetrate the freewheel mechanism. Provided the wheel is kept turning, you can add even more oil than that, and it won't spill out until the wheel is stopped.
If the freehub body has no seal in the LHS, you will know when the oil has fully penetrated the workings because it will start emerging from the LH end of the freehub body. If the oil is rust-coloured then you know that water has penetrated the mechanism. If there is a seal in the LH end of the freehub body then there will usually be a slight oozing instead.
A little corrosion in the freewheel mechanism is not the end of the world (under normal circumstances the bearing only
moves during freewwheeling, i.e. when it isn't loaded), but it is potentially problematic in that
a) if the bearings develop slack in them then this will only get worse; the bearing increasingly starts to scuff around when it isn't meant to be moving, i.e. during pedalling
b) the prevailing conditions inside the freehub body will tend to turn acidic whenever there is any rust present, which just encourages more corrosion; a vicious circle. Only removing all the rust or adding a lubricant with lots of corrosion inhibitors will stifle further corrosion.
c) the pawls are usually worked by a single spring that is typically made from steel piano wire that is in the range 0.25 to 0.5mm diameter. This can easily be seriously weakened or even broken by the effects of corrosion.
It appears obvious that if the lubricant is contaminated with particles of rust, it won't work properly any more. However it usually
isn't the abrasive wear rising from the particles (polishing is a likely outcome from this....) that is the main concern here; it is the chemical effect of the rust particles; this turns conditions acidic and this both promotes further corrosion and further degrades the lubricant; most oils and greases are designed to be slightly alkaline and when conditions change away from this, problems ensue.
Thus I recommend that a lubricant is used for this part which has got plenty of corrosion inhibitors in it; most lubricants (even some that say they do) have nowhere near enough of this kind of additive in them.
An alternative to this is to use oil and allow it to operate as a 'total loss' system, i.e. oil leaks out of the hub all the time and carries rust particles, dirt, water etc with it. This is how many bicycle bearings used to work, including SA hubs (when they were still fitted with an oiling port). This makes a mess but is usually effective at keeping the bearings in good working order.
A rough-running freehub bearing is genuinely not a big problem per se, but the free play in the bearing and the other things like the effects of corrosion on the pawl spring can be.
cheers
