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MG Midget and Sprite Technical - New take on Front Wheel Bearings!

I don't intend to raise the usual issues here - I have another problem!

I have the correct outer bearing. However the newer style bearings have a narrow outer race so on the outside the inner race stands proud. It also has a large radius on the leading edge of the outer race (leading as "during fitting")

I have wire wheels so the hub into which the bearing fits is very deep, with a long "fitted face". I am having great difficulty keeping the bearing square as the radius keeps encouraging it to go skew. Being deep down in the hub makes it dificult to keep an eye on the squareness. I am very nervous about it all locking up and becuase of the fact that the outer race is set behind the inner race face, using a madrel is not easy.

Can anyone offer a suggestion to assemble this lot? I wonder about heating the hub. If my calc is correct, gettingt the hub to 100 deg C should give me 2thou extra "clearance". Has anyone tried that?
G Williams (Graeme)

Use the old bearing outer as a drift, and just hit it harder. Eventually it will bottom out and square up.

I thought you were using nos from Bob?
Lawrence Slater

Yes I am using NOS. The outer bearing changed to a narrower race but still has the other attributes. I don't have a complete race for the "old" bearing and having cracked one race, I'm wary about whacking everything too hard! It is a real b*gg*r to keep square as it is about 3" down into the hub.
G Williams (Graeme)

Can you find a shaft that will slide down through the inner race that would act as a guide as you drift it into place?
Guy Weller

I had been using a socket as a drift Guy, but I guess if I went back to a blunt instrument then I may be able to get something through the centre.

THe socket was on an extenstion shaft and I was using my eye to keep the shaft nicely centred and vertical but it still had the tendency to kick over. It's that bl**dy large radius - why aren't these bearing made with small 1mm radii? (no, don't answer that!)
G Williams (Graeme)

I like the idea of heat! I wonder how the interference fit tolerance compares with the 2 thou? I could get it a bit hotter - 150 deg would give me 3 thou and might get another thou or thereabouts if I freeze the bearings.
It's going to fall right through at that rate!

Would I be allowed to put the hub in the domestic oven I wonder? And the bearing in the freezer?
G Williams (Graeme)

Ah yes, it's the outer bearing your talking about, not the outer of the inner. lol.

Have you got any 1/4" steel plate? Make a circular plate just smaller than the diameter of the bearing, and whack against that. I've got a piece if you don't have any. I could grind a bit into shape for you for.

Blow torch the hub, and leave the bearings outside. It is still winter after all. :)
Lawrence Slater

Wouldn't work Lawrence. This is a pic of the bearing (an MJT17) and you can see what I mean about the alignment of the faces. This is the outer face, the one against which load needs to be applied.


G Williams (Graeme)

This is the other side. Note the large radius! THis is presumably intended to cope with a radius in the seat location within the hub.


G Williams (Graeme)

Another option is to put your socket extension in a vice, upside down, and resting on the lower face of the vice. Put the large socket on the extension and the put the bearing on top.

Lower the hub onto the bearing and tap into place.

It might be easier to keep everything square that way.
Dave O'Neill2

I'll give that a try Dave
G Williams (Graeme)

I think your problem is the '11' in front of MJT17; IIRC originals were 3/MJT17. Not all MJT17s are equal!
David Smith

Yup, forgot about the way the centre is higher than the outer race. That is a big radius too. Must admit I've never noticed that, so maybe all my old ones are of the smaller radius.
Lawrence Slater

Once it's in it will be ok. The narrower race won't affect its performance. THe once which came out was the same style.
G Williams (Graeme)

No-one keen on the heat idea then?
G Williams (Graeme)

Not sure you really need heat Graeme. Plenty of people have installed these bearings with just a drift. That's all BMC advocate in the official manual.

This is the official bmc tool. Clearly you just hit it with a hammer.

I think you've become a bit reluctant to hit it hard enough. Understandable given the scarcity and cost of original rhp bearings. But in the end, I think that's what you have to do.





Lawrence Slater

Graeme, read this for encouragement.

I believe it was written by Rob. It's about installing new 40 degree face adjusted bearings and the reasons behind that, but in the lower section he also details the installation into the same hubs you have -- with pictures.

http://www.mgcars.org.uk/mgcc/midgetreg/Frontwheelbearings.shtml

Might give you more confidence seeing it in pictures and using a flat nosed punch.

Hope you don't mind me posting that here Rob.:)




Lawrence Slater

Installing outer bearings I usually get them started using the old bearing ensuring I'm keeping it square to start with.

When the old bearing is likely to get stuck into the hub I use an old piece of copper pipe flattened on one end and shaped to a curve to suit hub shape - then slowly tap the bearing (edge only) down carefully - side to side - moving at 90deg to ensure it does not bind - sort of feel thing.
Tapping rather than the FBH method !


Must admit never had to do a wire wheel one as yet - but the principle should be the same.



richard boobier

please try not to use a steel punch against a bearing, or if you do, please use only very small, gentle taps (never force a bearing with a steel driver)

of course, the hammer is steel, but the drift that transfers that hammer's force to the bearing itself, should be softer than steel

ideally, whatever is used to drive a bearing, when a hammer is the motive force, should be a softer drift material than the bearing itself (brass is ideal, because it is pretty hard, but will never dent the steel)

Believe it or not, it is really convenient to use sections of PVC pipe (available in a lot of diameters, if you cut from various stepped fittings). The material won't hold up to much abuse, but is tough enough for this task.


Norm
Norm Kerr

THanks Norm. Having broken an outer race I now realise how easy it is to do that. Ok I was removing an "old" bearing but am being very wary with the new one! I like Richard's idea of the flattenned copper tube too.
G Williams (Graeme)

Yes, I use the gentle tap-tap-tap method to get the bearing started. Not courageous (or foolish) enough for Lawrence's BFH method. Once "engaged" I then just use a large vice together with a suitable socket, to steadily squeeze the bearing into place. Worth knowing about the flattened coper pipe idea though; thanks Richard.
Guy Weller

Norm: found a bit of sink waste pipe just the right size.
Once the Mrs has finished the washing up, I'll take it out and give it a try.
G Williams (Graeme)

Guy,

Nothing original in this world - I think the copper tube flattened and curved came from Bristows resto book !
richard boobier

You're all mis-quoting me. I haven't suggested a bfh.

I have though said you have to hit it hard enough. Just tapping it lightly with insufficient force won't get it in, if it needs more force. I've NEVER broken one of these bearings either installing or removing them. I've used a flattened cold chisel on occasion (I've never used a "soft punch"), and not damaged the bearing at all -- as evidenced by the fact that all my bearings have lasted many many years after installation.

Tell you what Graeme, bring it over to me. I'll install it for you, and if I break it, I'll replace it. How about that?
Lawrence Slater

Another aid is if you have a well-worn flap wheel, you'll find it will just fit inside the "tube" and will ensure the id is clean. I'm also an advocate of the propane torch and freezer method.
M J Chapman

Graeme,

After all the options, have you got the outer bearing fitted yet?? If so what method did you use??
Bob Beaumont

"Another aid is if you have a well-worn flap wheel, you'll find it will just fit inside the "tube" and will ensure the id is clean."

MJ. It would have to be a VERY well worn flap wheel don't you think? I've never done that, and if others have, that could very well be the cause of "worn" hubs. I've only ever wiped mine out with a cloth and bit of petrol. If there are raised burrs from a previous bearing installation or removal, then better to use a thin file lightly to remove them, rather than risk removing metal from the rest of the insert.

I can smell that hub grease cooking in your oven from here Graeme. :)
Lawrence Slater

Not yet Bob..... totally confused!










G Williams (Graeme)

Update for those still following this exciting thread:

Bearings now fitted! Combination of plastic tube (but it split) and copper dolly. The outer bearing was very tight and kept going out of square but eventually succeeded! Need to try on hub spindle but this has been enough excitement for one afternoon, plus can't feel my fingers in the cold.
G Williams (Graeme)


I had the privilege of seeing Graham's outer beating at the pub (not hub) on Sunday. I think we discussed it at least twice in fact.

If it don't work I can give you the email address of the man who reckons to supply Genuine OEM Replacement MG Bearings (guess this applies to AH Sprite too).
And a quote from his email:-

'With these bearings (i.e. those he sells) your car passes the MOT. With the cheap unbranded rubbish sold on the net your wife gets to claim on your Life Insurance that much earlier'.

Quite a good joke if you know someone well but I've decided to look elsewhere!
Gavin Rowles

I think we discussed it at least three times! You probably don't remember the third time due to the glazed look you (and several others) seemed to adopt during the second discussion.

Nice marketing line though.
G Williams (Graeme)

So who is it Gavin? My email address is as above :).

Congrat's at losing your fwb virginity Graeme. :).
Lawrence Slater

Lawrence: did you ever try taking a dremmel to the small radius and chamfering it off?
G Williams (Graeme)

No Lawrence, this is the OTHER side. Had the first side apart a week or two back. Reused the bearings in time-honoured Lawrence fashion!
G Williams (Graeme)

Hi Graeme. Nope to the dremel, I haven't got a modern inner bearing to play with. Would some kind soul send me a freebie to play with?

I reckon it will work just fine.

Why wouldn't it work?
In one of the published docs, one by Tom Smith, -- "Some things I have learned about Spridget front wheel bearings" --, there's a discussion on this very topic. However, it's dismissed as unworkable due to the damage caused by "brinneling". ----- "The machining causes the balls or rollers to bounce around and produce a brinelling effect on the inside of the race. Even though the marks may be invisible to the naked eye these small dimples or creators caused by this brinelling effect on the race surface from the movement of the balls or rollers during machining can dramatically decrease bearing life. " ---- .

However ---.
I don't propose to grind an assembled bearing. I would separate the bearing and grind the inner of the outer race alone. Hence no damage to the raceway.

Ah but, you say. Separating the races and reassembling them damages the bearing. Does it? Is that proven? I've done it, and the bearings are fine afterwards. And I'm not the only one to have re-assembled their inner bearing after it came apart when pulling the hub to change a disc.

Here's why the bearing is ok afterwards, in my view.

Assuming you start with an assembled bearing --- 'out of the hub'. -- As you would be with a new 1mm radiused modern.
As you "pop" the inner from the outer, the balls don't dig into the raceway. They dig into the lip, which isn't in contact with the balls when the race is assembled and installed in the hub. Furthermore, only a couple/few of the balls dig into the race way. This is because the easiest way to separate the inner from the outer I've found, is to tilt the inner at an angle to the outer, and press the inner race out in that position. The VERY small dents in the outer race lip don't affect the raceway, and under my pocket microscope, I can't see any damage to the balls either.

Re-assembling the bearing is a reverse of the above, and makes use of the same previously created very small dents to let the balls pass the lip more easily.

Some of you may remember my renovated outer bearing, and the picture I posted of the dents in the lip. Here's a reminder.

So, if someone has a good modern inner bearing, with a 1mm radius, and would like to send it to me, I'll put it to use.

Or DIY it yourself.

Did you send yours back Graeme?




Lawrence Slater

Returned them to MGOC.
I'm suprised there is sufficient vibration to brinnel the race with a little dremel tool.
G Williams (Graeme)

Shame.

From that article, the brinneling was said to be likely if the bearing was machined at a factory post assembly. " -- bearing races can only be machined before the bearings are assembled. In fact that is how and when the radii on bearings are applied.".

Nobody else (as far as I know) has discussed disassembling the bearings and grinding them. If you took them to a machine shop, it might be too expensive, so a dremel or small hand grinder would be the way to go I reckon.

If you did the grinding with the bearing assembled, you risk contamination with metal dust getting into the grease and becoming a grinding paste. You could wash them out with petrol, but since it's so easy to take them apart, that's how I would do it.
Lawrence Slater

separating a bearing, you are probably correct, might not cause any damage that matters.

Or it might, over the long run.

The bearing manufacturers recommend that they not be separated, but when you talk with their tech department they admit that they can't be sure if one that has had that done to it is no longer any good (as Lawrence pointed out, if the damage was suffiently outside of the wear path, it might not matter), only that it is not meant to be done, because it might matter.

For instance, when I found a company in New York that specializes in re-machining existing bearings for unique applications (our issue is not unique, in the world of repairing existing machinery). They said that they do not separate bearings to machine them, they use special rubber clamping rings which hold the balls still while the machining is being done.

Companies that need to repair a million dollar machine, and need some bearings specially modified to work with the situation they have, don't mind that it costs $100 to do this to each bearing, but it seemed high in our case, compared with our other options.

I bet that a person who used a dremel to grind a 2mm radius into a bearing of theirs might be OK, and if that person chose to separate it first, they might also be OK. Or, if there is a durability problem after having done so, it might still not matter over the kind of miles a restored classic car is most likely to see over the next 10 years.

It is like using a torque wrench. Some folks use one all of the time because it takes the guess work out of a project. Others don't ever use one and think people who worry about torque are fussy. The fact that those people's cars mostly turn out OK is a testament to how much margin is designed into cars by the original designers, and to luck.

Norm
Norm Kerr

Interesting Norm.

I wish I had a need to replace my bearings, and or didn't already have some nos rhps. I'd love to do this just to prove it's worth -- or not as the case may be. But I reckon my money is on it working perfectly well.

Thinking about it some more, the balls couldn't rattle around(much if at all) anyway if the bearing was packed in grease.

That leaves the problem of contamination. So as long as a way was found to keep the grease clean (some kind of shield glued temporarily in place), the grinding/filing could be attempted on an assembled bearing, thus removing any risk of damage.

What ya think?
Lawrence Slater

This thread was discussed between 23/03/2013 and 26/03/2013

MG Midget and Sprite Technical index

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