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MG Midget and Sprite Technical - wheel play along rear axle axis?

Hi all

MOT due some time this month, so I was doing a cursory poke about and found that I've got play in the rear somewhere that's along the axle line. No play up and down or side to side, but I can pull the wheels (on both sides) in and out a bit. Rocking the car (fairly vigorously) results in a clonky noise, but there's no grumbly bearing noise or obvious bearing noises on cornering.

What's that all about? Rear wheel bearings? something more 'interesting'? It'll be the first time I've had wear in the rear end (shush) so I don't know what to look for other than 'normal' bearing wear, but I suspect the halfshaft will mask that by making it hard to move the wheel up and down.

Don't see why it's worn out, I drive sedately everywhere...

thanks!
Rob Armstrong

From the symptoms you describe, it sounds like either worn bearings, or the bearing moving on the axle.

You are correct that the halfshaft being in situ will tend to mask wear in the bearing. You really need to pull the shafts to see how bad the bearings are.
Dave O'Neill2

"I can pull the wheels (on both sides)"

That's the clue then. The only way you can do that, is if there's wear in the bearings allowing the outer races to move sideways relative to the inners, or the hub nuts are loose, allowing the inners to slide back and forth on the axle.

So now you'll be able to buy some Moss, or Sussex, or whatever moderns, and help to confirm that they are a proper fit on the axles. :).

There's always a positive opportunity in life's little challenges. You just have to look for them.

Always look on the bright side of life.

1 minute 3 seconds in.

http://www.youtube.com/watch?v=eTXiqKGFNso
Lawrence Slater

If you've used a gasket between the bearing carrier and the halfshaft that is too thick then the bearing isn't going to be clamped tightly. It might be that slack that you can feel?
Hard to describe but the hole in the carrier that the bearing sits in is 'X' mill deep and the bearing is 'Y' mill thick. If X and Y were the same then you would find the halfshaft would perfectly clamp the bearing tightly. You need a paper gasket to stop leaks so the depth of the hole in the carrier must be shallower by the thickness of the correct gasket paper. If the paper is too thick then the halfshaft is kept from clamping the bearing in position.
r thomas

thanks chaps, more studying of the exploded picture in the book of lies has cleared things up as well.

I'll let you know how I get on! I haven't had the halfshafts out since I went K, so will be interesting to see how the splines are doing. The last one I took out a while ago had an alarming twist in it...

Hope the garage is wide enough to get one shaft out of the axle...
Rob Armstrong

Agreeing, but my guess is that the large nut is loose, allowing the bearing inner race to move in an out along the axis of the axle. From your description of pulling the wheel in and out sounds like more movement than slack between the half shaft and hub caused by the wrong paper thickness. And lack of rocking or vertical movement implies to me that the bearing itself, though loose, is not worn.

There's a nice photo somewhere (maybe in Spritley Years ?) of a competition Sprite with one rear wheel coming off as the halfshaft and hub assembly work their way out of the end of the axle tube.
Guy W

I agree with Guy - the most probable cause is the large nut on the end of the axle spigot has come loose. The captive washer is fairly ineffectual in that a small tongue should sit in a hole in the spigot. I found that tightening the nut creates sufficient torque to tear the tongue out of the locking hole. Even when the outside tabs are bent over, it wont lock.
AS long as you don't have a RWA I don't think the wheel can come off :-)
Make a mess of the body work though.
I'm sure you are aware that the two nuts are left and right hand threads!

I think Rob I would be wary of the half shaft starting to fail. I guess it's the inner end going and if that does give way it creates a load of shrapnel inside the diff or at best it can be a real s*d to get out of the drive pinion.
G Williams (Graeme)

The worst part about this repair, is finding a wrench to fit that 1/8th inch wide HUGE freaken nut

I special ordered a socket and cost around $40 ....pretty much a 1 time used tool, just sits in the corner of the tool rack to big to be used for anything other then a paper weight

I got to think its the paper gasket as well, the thickness has to be dead on, or problems will mount up

Prop
Prop and the Blackhole Midget

"The worst part about this repair, is finding a wrench to fit that 1/8th inch wide HUGE freaken nut" No Prop. stilsons fit perfectly well. wanna see a picture? lol. It's an easy and very quick job, if not replacing the oil seal too. And even then that only adds a little more time and a little hassle.

The nut may well be loose as I said earlier, but if the lock washer tag is knackered, then the tendancy would be to tighten up not slacken off. This is due to the rotation of the wheel being forwards most of the time, and not reversed. That's why the left hand side of the car has a left hand thread on the axle. If the lockwasher fails, the tendancy would be to tighten up, not loosen off. And given the depth of the thread, you'd know long before the wheel fell off, even if the nut was that loose.

As for the paper thickness, the outer race of the bearing is supposed to be a tight press fit in the hub. It shouldn't rely on the paper thickness(thinness) to keep it in. The paper would also have to be pretty thick relative to the standard gasket, to allow you to move the wheel noticeably in and out. If it's loose enough to slide in and out, then the hub's in need of attention or replacing.

But given that Rob's been driving this for some time, and the "in out" has only just been noticed, something has changed, and most likely it's wear in something.
Lawrence Slater

Rob's probably just not tightened his wheel nuts for a while. You know what these K drivers are like!
Guy W

ha! wheel nuts are always nicely tightened after I didn't once and a front wheel fell off.

It'd be nice if it just needed tightening up, but I suspect that the threads are designed to keep the nuts on so it's probably bearings. It's also fairly recent.

I have a set of Stilsons in the background, just waiting. Sometimes just the threat of them works.
Rob Armstrong

Come on Rob, it only takes five minutes to remove a brake drum and pull a halfshaft.

Don't keep us all dangling, waiting for the answer!
Dave O'Neill2

A while back, when first discovering the large axle nuts, one of mine was loose- not even finger tight. And the axle was the correct way round, so I don't subscribe to the self tightening idea. I think all that happens is the nut doesn't fall off quite as quickly as if it had the "other" thread. If the whole assembly is "working" at the nut because of a bit of movement, it's going to work its way off.
G Williams (Graeme)

No, I don't think it self-tightens.

The theory is that it won't loosen if fully tightened. If it is loose, it will loosen more.
Dave O'Neill2

I don't think anyone said the nuts are self tightening. They aren't. But clearly the LH side has a LH thread for a reason. That must be an attempt at least, to counter the tendancy for the nut to unwind if it were left loose on assembly. Likewise the conventional direction on the RH side. This exact nut arrangement was used on an awful lot of different BMC cars over the years, and if it was common for nuts to unwind and hubs to fall off, I reckon they would have altered it sometime. But they didn't, and I've never heard of anyone having a hub fall off, even if their nuts weren't fully tight.

If I recall from your thread Graeme, didn't you discover that the nut on your axle was partially stripped, or the axle thread was? So it's not surprising that the nut wasn't tight.

As for my own 37 years with the same Sprite. In all that time, I've never found my rear hub nut(s) loose, and I don't renew either the nut or the lock washer.

Lawrence Slater

I reckon the theory is exactly the same as for wire wheel spinners, which do self-tighten while going forwards, and will unscrew themselves when the car is reversing. Hence the use of locktabs on the axle nuts to prevent natural movement.
David Smith

The Austin A30 has a RH thread on the LH side. I discovered this after spending sme considerable time trrying to undo one.

I also recall reading in 'More Healeys' that the first Frogeyes had the same arrangement and they had problems with them coming undone.
Dave O'Neill2

"then the tendancy would be to tighten up not slacken off"

Doesn't that imply "self tightening" (but that is being pedantic - apologies!).

Knock-off spinners are heavy items and which develop a high rotational inertia and will have a tendency to "keep on rotating" after the wheel slows down (a bit like a flywheel). So if there is any looseness this inertia will overcome it.

THe lightweight nuts on the axles are a totally different issue because they don't rotate in the first place but could potentially be dragged around by the proximity of rotating items. Not much in the way of forces being developed unless the outer bearing race could somehow catch it. The nut threads are handed but IIRC are the other way around to the wheel spinners. I think that means RH thread on the right hand side, as Lawrence says and not as Dave suggests. Worth checking (Manual, not handbook!) as there isn't enough thread to see and make a judgement. And if you refer to "Restoring Sprites and midgets (Bristow) it is IIRC incorrectly stated.

Lawrence: one side on my axle had a bad thread but was pretty tight when I removed it. But the thread failed (I suspect in the nut)when I reassembled at a low torque of about 25/30 ft lbs. I guess it could have been loctited previously. When I replaced the bearing on the other side that nut was slack by about half a turn.
G Williams (Graeme)

Perhaps I didn't make myself clear - the A30 had RH threads on both sides, as did early Frogs. Later Spridgets have LH thread on the LH side.

You don't need to look at the thread, it is actually stamped on the face of the nut.
Dave O'Neill2

Hmm, that's a good point though Graeme. What apart from circulating air, would make the nuts revolve, -- in either direction, if they were loose? As you say the nut isn't in contact with any moving part. So on the face of it there's nothing to prevent the nut vibrating looser still.

But on the other hand, consider this.

If the nut were loose, AND the lockwasher tag no longer engaged in the axle, 'AND', the inner race of the bearing was a loose fit on the axle -- allowing it to slide in and out, then, it's quite possible(maybe probable?) that the inner race, dragged around by the outer race, would rotate too, in the same direction the wheel is turning. So as it would be in contact with the hub nut via the now free to turn "lockwasher", it would tend to prevent at least, the nut undoing any further.

Or consider this.

The bearing is meant to be a press fit both in the hub and onto the axle. Assuming both conditions are met, then even if the nut was loose the bearing would stay in place, for some time at least. Thus the hub would stay in position. Then if due to vibration AND a failed lock washer, the nut unwound, it would only get as far as contact with the inner face of the half-shaft. The shaft is turning in the same direction as the wheel, and would tend to re-tighten the nut every time the two made contact.

I think the main point is this. If the bearing and axle are in good condition -- as they should be, then the hub (with bearing) will be a press fit on the axle and won't move on it's own. Assuming a lock washer with a decent tag is used, and is folded over the nut, which is properly tight in the first place, -- all of which should be the case, then the nut won't unwind.

If the nut is loose, it's for a reason, and even if it is, it's hard to see how it could come off completely.

But I reckon it's the basis of a worthy experiment. take an axle, unwind the nut a fair way, and go for a drive. lol.

Lawrence Slater

Lawrence,

<<The bearing is meant to be a press fit both in the hub and onto the axle.>>

Do you know that for a fact? Have you any BMC documentation to that effect. Bearings such as the hub bearing are often a sliding fit in one item and press on another. IIRC there's a table for such fittings in the SKF catalogue. It's been a few years since I fitted a hub bearing but they never seemed to be a press fit on the axle but rather slide on, that doesn't concern me as the nut is there to hold it on.
David Billington

In my limited experience (one pair of hubs, 2 axles) the bearings were a light slide on both inner and outer. A secondary but important job of the nut is to lock the inner race on the journal. If the inner race creeps as the outer race turns it can lead to fretting and journal wear. Having worked for a company which was very reluctant to allow my maintenance team to access a bearing while it still appeared to be serviceable, I have seen unbelievable journal wear because bearings have been turning on the seat. It doesn't need to "spin" - just creeping round will do it although as wear takes place the bearing starts to turn more readily.
G Williams (Graeme)

The hub requires a puller to remove and drifting back on according to the workshop manual and the bearing is a press fit in the hub.

Also the half shaft cap is intended to clamp the bearing race by between 1 and 4 thou and the paper gasket must be compressed before the shaft abutment shoulder pulls up on the races. A thickness of 10 thou is recommended for the gasket.

Chris at Octarine Services

Chris: probably was 40 odd years ago. Not sure many still meet that spec. Mine were a mixture of "tap in" fit to "slide" (not "loose and rattling about" but def not press fit). The halfshaft may grip the outer race, but the inner still depends on the combination of fit and nut to prevent rotation. The fact that there are two clamping systems as backup(one for each race) should take a single reliance off the fit quality as long as the bearing doesn't wobble about.
G Williams (Graeme)

dangle no longer.

2 hub bearings with lots of play, in and out and wobbly, worse on the driver's side, it can go in and out until it hits the brake cylinder. Nuts are good and tight with lock tab things intact.

Oil's got out of one end and ruined the shoes on the passenger side, but they've only got a couple of mm left anyway so it's time for new ones in any case.

One half shaft is as straight as a die (driver's side), the other one has a very small twist in the splines (inner end about 1mm rotated from the rest)

I had forgotten how smelly the oil is...

Rob Armstrong

Congrats Rob. Now whose bearings ya gonna use?


Hi David, Chris of Octarine beat me to it.

The official bmc workshop manual gives the tool part numbers for pulling the hub and the bearing. I've never seen them though.

Also. Mine are a tight fit on the axle and in the hub both sides. And, years and years ago, I went to my local bmc dealer in Balham london, to ask how the rear hub bearings were removed. They told me they were a press fit and I needed a puller. But as I wasn't about buy a puller, they told me to just use the brake drum as a slide hammer, and whack the centre of the bearing to remove it from the hub, as it was being replaced anyway.

It's my view, that any bearings that are loose in the hubs, or loose on the axle, is down to some previous action by either a garage or an owner some time in the past.

If the bearings were fitted properly, and the nut always tight, I don't see how wear could occur. And yes I've read about bearing creep. But if mine and many others are still not worn, then others shouldn't be either, even if they are 40/50 years old.


Lawrence Slater

But the point is that the nut isn't always tight resulting in a bit of wear. Bound to have happened in the 35 to 50 years of the car's life. Also not many owners have a suitable socket and so tightening the nut can be a bit hit and miss even with mole grips/stilsons/engineer'v vice or cold chisel and hammer.

These are the rear bearings so there isn't a supply issue. Just from the so-called popular metric range and available "everywhere". If I'm looking at the right invoice it should be a 6207 and a W25017537 R21 lip seal.
About £20 for both sides (SKF)
G Williams (Graeme)

Lawrence,

Have you seen Rob drive his K? It would be very apparent how wear could occur with the lateral loads he puts through them keeping up with other K's with 60Bhp more than his own.

Rob 'getaway driver' physicist Armstrong.
Johnathan

Of course Graeme. If people don't do the nut up properly, just as on any system designed with certain conditions in mind, if people don't comply with those conditions, then odd wear will occur where it's not supposed to. It goes without saying that the nut is supposed to be done up tight, just as mine has always been, -- with stilsons --- , and others have been using other means, including the correct socket.

The point I was making is that the axles aren't worn out because they've been in use for 40/50 years. To imply wear is inevitable and due to age doesn't stack up. It's down to incorrect assembly.

Johnathan, the wear I was referring to was on the axle shaft and in the hubs, not in the bearings themselves, which of course eventually wear out, however the car is driven.
Lawrence Slater

one of the hubs is a bit worn out, slightly ridgey on the inside, but not beyond loctite mending for re-assembly, but everything came to bits quite well. Axles seem fine and the seal place is all good.

a normal puller works just as well as the 'recommended tool'. And bonus manky toes (which were safely covered during actual work)







Rob Armstrong

Was it only your naked toes exposed during that photo shoot?

Good job nothing else was in the frame. lol.
Lawrence Slater

" I've never heard of anyone having a hub fall off, even if their nuts weren't fully tight."
I did once, in fact was there to witness it. Car took off from the start of a hillclimb and we watched in amazed mirth as the wheel gradually moved further and further out, then the whole lot inculding the halfshaft cam adrift and carreid on down the road while the car came to a ginding halt!! Obviously not a square arch Midget!

Rob: I've been down the Loctite route. While I am a great fan of the product, in this application it doesn't last long and I was having to re-do it after every serious event. The Loctite (and I was using one of the higher grade ones) just seems to break up. I think at least part of the problem is getting enough pinch on the bearing outer as described by Chris in his post on the 7th as once the bearing has been shuffling in the hub the inner face wears too (as witnessed by its moving in and out).

I had to persevere with it because it was on the B and the B unhelpfully has 1/2" studs and so second hand hubs from saloon cars etc were no use (the B hub was made slightly bigger to accomodate the larger studs) and new hubs weren't available at the time.

I finally got a permanent cure when Brown and Gammons commissioned new hubs. After that, problem gone.

Given how the A series hubs were used in the same form in many applications, second hand is a viable option so I would definitely seek a couple of good ones out if I was in your situation, expecially with a heavy right foot and a bit of K power!
Paul Walbran

Paul,

Your mention of problems with Loctite failing reminds me of similar problems mentioned by ex UK racer Terry Sanger. IIRC the Loctite seemed an ideal solution but failed frequently, in the end it was realised that the fatigue characteristics of the Loctite were poor and led to the failure in the application which was similar to the hub bearing.
David Billington

Rob

I have some spare hubs, if you need them.

daveo138 AT yahoo co uk
Dave O'Neill2

Rob,

Some more inappropriate footwear, this was my mate when we were testing a brake drum forge I made for his 51st birthday
David Billington

Rob,

Looks like I forgot the picture so now attached.

Some more inappropriate footwear, this was my mate when we were testing a brake drum forge I made for his 51st birthday


David Billington

update - one's back together and no play. Am awaiting a good less twisted halfshaft to put in the other side. How do you tell if it's a lefty or a righty?
Rob Armstrong

Brake drum forge? Are you sure that isn't a BBQ?
Guy W

Doesn't look big enough for a BBQ, that. Unless you have small sausages...

all back together, no play. Here's a pic of the half shaft I didn't put back in next to the one I did. Good job I check them nice and regularly. That was straight when it went in last time, around 2.5 years ago.






Rob Armstrong

Guy,

IIRC a 9" drum off the back of an Opel GT, kindly donated by the local VW garage owner. Might be OK as a small BBQ until it got fully hot, after that you'd quickly end up with charred remains, actually that's normal for some BBQs, quite easily heated the steel we were forging. I've yet to make mine but did scrounge some front drums off a Land Rover from a local chap, IIRC around 12".
David Billington

Rob
Was your replacement half shaft the same length as the splines look longer on the twisted one.
M Myers

Shaft is exactly the same total length but the splines that are on the old one are about 3mm longer, strangely. The 'new' one is an en17 one (it says so on the end), the old one might say mowog on it but it's hard to tell.
Rob Armstrong

It may also say BTA806 on the end. As they both have the groove near the end, they are both 1275/1500 type shafts.
Dave O'Neill2

This thread was discussed between 04/08/2013 and 13/08/2013

MG Midget and Sprite Technical index

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