RobThomas wrote:Anyway, the gasket needs, IIRC, to be
just enough to bridge the gap between the black bearing carrier and the blue halfshaft or else the red bearing has a space to move sideways. I recall that the bearing, once pressed into position, sits slightly proud of the carrier and that the paper gasket holds the halfshaft away from the carrier just enough to ensure that the flat face of the halfshaft touches both the paper and the bearing by equal amounts. Does this make sense? If so, a gasket which is too thick would increase the clearance between the carrier and halfshaft and give space for the bearing to move sideways.[frame]
[/frame]
This makes perfect sense, Rob, and is spot on in my opinion. All this talk about faulty bearings and incorrectly fitted bearings and bearings of the wrong size is way off the mark.
Thanks for taking the time to do a diagram and make such a positive contribution to the thread.
You grab the issue fully by the horns when you write:
"....just enough to ensure that the flat face of the halfshaft touches both the paper and the bearing by equal amounts."
Indeed! I now believe this is the source of the problems of leaking halfshaft seals on so many Moggies. How the heck can you set it all up so you have these exactly equal amounts - the seal must be compressed by the halfshaft, but the halfshaft must be in contact with the outer bearing face. We're talking NASA space tolerances here! The seal must become compressed sufficiently by the halfshaft to allow it to be an effective seal, but if it's not compressed enough the halfshaft won't make contact with the hub bearing outer ring. If the seal not compressed enough and the halfshaft flange doesn't contact the bearing outer ring, then oil could leak past it AND allow lateral forces form the wheel to start acting upon the hub, instead of the bearing.The hub gets pushed inwards during a turn inwards whilst the bearing doesn't move....the hub starts to slide about.
So, having dry rear brakes - pot luck!
I'm posting this because I wanted to thank Rob for his input and congratulate him on his accurately figuring stuff out for himself. I've reached and posted about my final conclusions in another place, but I've given up there also because I find the quality of the replies just as grim as they were here early in this thread
....there's a kind of general nit-picking vibe in both forums and nothing in the way of "Hey mate, thanks for taking the time to do all this."
Like....nothing at all.
Sad.
Good one, Rob! Happy motoring! May your tyres never wear out!
Here are my final conclusions - posted up because I feel the issues discussed are important and I've never seen anything as detailed as this on the web regarding rear hubs/halfshaft flange oil leaks etc:
Let's now discuss the reasons why there is no retaining circlip to hold the hub in the correct position on its bearing and why the original hub/halfshaft flange paper gasket is so thin.
Like most things, it's all so obvious with hindsight. I have read in Moggie forums that the hub bearing must be flush with the hub flange face. This is not true. The bearing is a little proud of it - there's a small (very small) step that can be checked with a straight edge. Your eyes and fingers might tell you it's flush.
My cigarette paper test stuck in my mind. The reason for the small step is to allow room for the original thin paper gasket or the large O-ring. The fact is that the half-shaft flange bears on the outer ring of the bearing. It must be in contact with it. An O-ring if fitted would be compressed but still proud of the groove in which it sits, thus continuing to act as a seal.
Now, if you get wet brakes and take off the halfshaft to change the gasket, and think "Hmm, this is too thin for purpose, no wonder it's leaking", and proceed to make and fit a thicker gasket, the half-shaft flange will no longer be in contact with the outer ring of the bearing.
Get it?
With a thicker gasket, the lateral forces of the wheel will be bearing on the hub instead of on the bearing outer ring!
You can check yourself next time you have the half-shaft out. Remove the hub/halfshaft flange gasket, and clean the mating surfaces. Fully insert the halfshaft, and note the small gap between the halfshaft flange and the hub. That's the space for the original thin paper gasket.
On the axle I've been mulling over, someone had fitted, on each hub, a thicker, home-made gasket on top of an O-ring! Both hubs were sliding! The lateral forces from the wheel had been on the hub, not the bearing.
This is the reason why there is no circlip to maintain the hub in the correct position on the bearing - one might say the hub, in the orginal design, is passive regarding lateral forces. Fitting a thicker hub/halfshaft gasket makes the hub active in respect of the lateral forces from the wheel. With a thicker gasket, the lateral forces from the road wheel are pushing against the hub - no wonder it can start to slide on its bearing!
So the setup is not "footballs" after all Smile. It makes sense.
The ultimate conclusion is that the large O-ring is the better seal to use if your hub has the groove in which it sits. Otherwise, always use a new original thin paper gasket. I've seen so many thick, home-made hub/halfshaft flange gaskets, and....er.....um....yes....well....have done the same thing myself Rolling Eyes, more than once, I can tell you.
I've read forum posts by bmcecosse in which he's written that he's never had any problems with rear hubs in all his years of owning and running a Morris Minor. He advises the use of the large O-ring as a seal, without the thin paper gasket.
I reckon he is absolutely spot on!
Owners whose rear hubs do not have the groove for the O-ring have a second-best setup, in my opinion.
So, in conclusion, the lateral path of force from a rear road wheel should be:
wheel > halfshaft flange > hub bearing outer ring > step between axle casing and stub axle....where they come to a dead stop.
Lateral force on the hub itself: zero.
In a simple sentence, then:
Using hub /halfshaft flange seals of non-standard dimension (ie too thick) can result in rear hubs becoming loose on their bearings.
There! I can now sit in the shade and down a couple of very cold, extremely tasty, high-quality Polish beers, and gaze up through the blue beyond the trees, and think of nothing much at all.
(Some of my earlier posts here contain thoughts and ideas which are either wrong or irrelevant....it's a process, after all).
Moving on now to the goal - how to minimize the chances of having oil leaking past the hub/halfshaft flange seal. A lot of Moggie owners have posted about this problem on the web and for some the leak persists after many attempts to stop it.
My take on it is as follows....
Before the wheel goes on, the half shaft is held to the hub by a small screw. When the screw is tightened, it will compress the seal, be it an O-ring or a thin paper gasket, to some degree. When the wheel is fitted and the four nuts tightened to the correct torque, the seal will become further compressed. So whatever the torque put on the small screw, it will now be reduced as the halfshaft is pushed closer towards the hub by the force of the wheel nuts. There would be a small gap between the bottom of the screw head and its conical seat in the halfshaft flange - the halfshaft moves inwards, but the screw stays in the same position.
When the wheel is removed, for a change after a puncture say, the pressure of the halfshaft on the seal is released. The seal is no longer clamped as tight as it was between the hub and the halfshaft flange. Oil and perhaps some debris are allowed on to the previously dry top side of the seal. The wheel is put back on and the nuts tighted. But the state of the seal has been changed.
All this is based on the assumption that there's no way to get the same pressure on the seal from the halfshaft flange using a screwdriver on the small screw as it is from the four wheel nuts loaded up using the correct tool.
One way to avoid this "de-clamping" of the seal when a wheel is removed would be to have a small hole in the wheel which exposes the head of the small screw when the wheel is in position. The small screw would be tightened before the wheel went on, and again after the wheel nuts had been fully tightened. Assuming the screw hadn't moved due to vibration, there would be no recuction in halfshaft flange pressure on the seal the next time the wheel was removed. No altered state. The wheel would go back on, and everything would be just as it was before it came off.
Another method would be, with the wheel off, to use the four wheel nuts to clamp the halfshaft flange to the hub, and then tighten the small screw. Thick washers should first be placed under each nut, since the nuts would travel further along their threads than usual. The nuts should be torqued to the same amount as that applied to them when the wheel is eventually fitted. Remove the four nuts and fit the wheel.
The alternative, if you don't want to rely on a seal whose state has been altered, is to renew the seal every time a rear wheel is taken off.
