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MG Midget and Sprite Technical - wheel bearing

I'm afaid i made a mistake fitting my front wheel bearings.
And i don't have a haynes here.

The standard ball bearings have two sides.
push inner part side A and it just compresses the bearing
push inner part side B and you push it all a part

The outer (outerside of the car) one is clear to me this has to be compressed with the central nut.

the inner one has me puzzeld
does it has to be compressed by the spacer in between or should it be the other way around?
and if it's the other way what compresses it isn't there only the seal on that side?

And now the big question does it mater?
Incresed wear? at what rate?
Or wil it pop out under load?

I run wire's with the factory conversion so no crazy adaptors just splined hubs
o Könemann

Just spent maybe half an hour trying to find an illustration of how they are assembled without success. As an engineer it has always been obvious which way round they go as I know how they work but a picture would make it far clearer and I haven't found one yet. Maybe tomorrow or someone else will sort it.

If it helps the spacer is there to set the gap between the races and balls to prevent excessive clamping so the inner races clamp the inner spacer.
David Billington

so if i understand correctly i've screw it up again

the spacer is there to keep the ballbearings from taking to mutch side load
and not to compres the inner bearing

ive been searching for a pic to but my standart manual site (spridget tech) is down
o Könemann

A step-by-step photographed procedure uploaded to a website would be useful. I've been wondering if I did mine right ever since I fitted it, even though I took advice and pored over the archives. Still, it's been alright for the last 700 miles or so so fingers crossed!
Jordan Gibson

The attached should give you an idea of the arrangement used. The spacer fits between the inner races. Hopefully you can see how the bearings work and with this arrangement the hub can't go anywhere. Also why the manual says if the outer races are marked thrust they face each other and if the inner races are marked thrust they face away from each other as each angular contact bearing is only intended to take load in one direction.


David Billington

yep it's clear to me i've screwd up again

my new bearings didn't have anny markings bit strange in all
o Könemann

Just in case it's not clear the hub is indicated at the top by the AB and the shaft(stubaxle) at the bottom. I should have clipped the face-to-face text as that is for a different arrangement.
David Billington

David are you sure? I agree the spacer goes between the inner races but in the drawing the inner races cannot move towards each other because of the balls and the outer races being held by a rebate (or whatever its called) in the hub so the spacer would not perform any function. (but it might be that I don't understand all the forces involved, and where they need to be transferred to!)
David Smith

David,

It looks fine to me. The balls and races govern the distance between the inner races and the spacer is slightly longer than that distance if a gap is to be maintained or slightly shorter if preload is required.
David Billington

I always think of it as: tap each bearing into the hub with the 'closed' side inner-most; and before you tap the second one in, don't forget to fit the spacer.

The nut clamps the bearing inners, and should give the balls a small pre-load (they should spin easily).

A
Anthony

Still puzzled, and am doing this job NOW!

My bearings are both marked Thrust on the outer race of the bearings. I assume therefore that these two "thrust" sides need to face back to back in the hub, otherwise there is nothing for them to thrust against.

If a section through the outer race looks like a letter J on its side then the bottom curves of the J point towards each other. The slimmer edge of the bearings point away from each other. Am I right, before I go and assemble it this way!

Guy
Guy Weller

Guy,

That sounds right to me from what you said.
David Billington

I just whipped up a quick sketch that may - or may not - be clearer than David's scan above.

I like to clarify things by thinking of the stub axle and the inside bearing races as forming a letter H, with the balls restrained by the vertical legs. Hopefully the drawing will help!

This topic has come up before, and for some reason it's simple to imagine, but very difficult to explain!

Note too that on some bearing sets, like the ones I fitted, the "wide" face of the outboard bearing, as illustrated in the sketch, doesn't look all that wide. So check the inside face of the outboard outer race to make sure it's wide.

-:G:-


Gryf Ketcherside

Thanks Gryf, and David.
That is how I have just done it and it is all back together again now. Hopefully, the wheeel won't fall off!

Guy
I will now complete the tale on my original thread about which side was worn!
Guy Weller

Oh, well the other thread has dropped into archives so I cannot add to it.
Interestingly the noisy / worn one turned out to be the one on the INSIDE of the turn. i.e. not the one that had the extra cornering load on it when turning.

Not what I expected and opposite to the collective BBS wisdom. A local garage man had said that ball type wheel bearings go quieter when loaded and that this is opposite to what happens with roller bearings which go noisier when loaded (if worn) Seems he was right!

OR it could just be random!

Guy
Guy Weller

Di I dream it or did I read somewhere that it is possible to convert from BB to roller taper bearings? If so, anyone got details?
Chris
Chris H (1970 Midget 1275)

Chris,

No, you didn't dream it. It can be done. I did it many years ago and haven't looked back. Check the archives for the part numbers.

Martin
Martin

Martin

Any clues on the year of the thread, have looked but cant find it

Alex
Alex Sturgeon

It was some time in the last year or so. Since I'm at work, I can't do anything but when I get home I'll dig out the numbers and post them. Isn't the 8 hour time difference great? I'm still at work for another hour and you're headed for bed.

Martin
Martin

If you use the search parameter "use all words" with the search phrase "tapered wheel bearings timken" it will find the relevant threads.
Graham P

The magic numbers are

Outer cone (small bearing) 05066

Outer race (for small bearing) 05185

Inner cone (big Bearing) 07097

Inner race (for big bearing) 07204


These are all Timkin numbers but any decent place should be able to cross reference them to SKF or whoever.
Martin

Obvious next question

How many of us are running on these or equivalents?

it'd be worth the small outlay just to remove the constant whining from un-acquainted MOT testers that "the wheel bearings are shot" when we know they are not!

do we:

"Discard centre spacers and tighten as normal taper bearing sets"?

Any recommended torque settings or:

"just tight and add split pin on a castle nut"?

I am seriously giving this a lot of thought
Bill

Bill I think you are being a little unfair upon MOT testers. Thw wheel bearings with excessive play should be failed. The problems for us is that the modern equivalents of the original wheel bearings are not the same as the originals and are therefore not made to the same tollerances. (I do have an engineering drawing of the original bearing spec and it is different to modern equivalents). thus we should be modifying the spacer to suit the new bearing tollerances but that is not easy to do correctly.

The taper bearing as you say is a far better "fix" and should be encouraged.
Bob (robert) Midget Turbo

Thanks for that Martin, and do you have a reply to Bills question two above this one.

Alex


Alex Sturgeon

These numbers are what I have on my auto-X car. I think I put the spacer in. Tighten and back off one flat. DO NOT use the numbers on the Timken website. They stick out about 1/16". I did have a set of washers ground down before I got the correct bearings. A bit pricey. Mine from Mini Mania USA.
J Bubela

I use the tapered bearings on all my Spridgets. No spacer; it is not needed and could cause problems in the process of getting it to sit "correctly". Yes, some truck axles do use a spacer that looks vaguely similar to strengthen the axle, but the torque required for the spacer to actually add any strength to the stub axle greatly exceeds the torque that would strip the axle nut on our Spridgets.

I agree with midget Bob up there that if the original bearings were available with the original tolerances, I would stick with the originals. HOWEVER, since they are not, I have no regrets about going to tapered roller bearings.
David "Roll On" Lieb
David Lieb

I quite agree about the bearings we get now as against the "olden days" ones.

But some MOT testers?

I reserve my judgement


Most ARE good

but...
Bill

If using tapered bearings, do the hubs need machining, or is it more or less a straigyht swap? I've been reading and re reading the archives but is as clear as mud!
Graham P

The spacer is not required and as far as how tight, it's one of those things that you have to "feel" as opposed to a given number. Since I've delt with tapered bearings for over 40 years, I've learned how far to tighten them. Basicaly, you tighten the nut until you get no rocking motion of the hub and back off the nut until you can insert the retaining pin. The hub should spin freely with no obvious binding.

The thing that I like about the tapered bearings is the manufacturing tolerances are not a factor in proper assembly as they are with the ball bearings. If one bearing or race is bigger or smaller, the difference is easily removed by the tightening of the retaining nut.

N.B. The spindle has two holes for the retaining pin 90 degrees apart which gives you some leeway for locating the nut.

Martin
Martin

Sorry Bill you have not understood the point I was making. Modern bearings are far superior to those of yesterday but!!

The bearings specified by BMC/BL were specials that are not made today. The modern equivalent whilst appearing identical have just not the same tolerances applied. Thus the tolerance spacer requires adjustment when used with modern equivalents, which we are all aware of.

I think even though the vast majority of bearings today are not made in the "Black country" with modern materials, processes and machinery all bearings of today are far better. The problem is that in a chase for price why make something to a high specification tolerance if it is not required? A couple of thousand Spridget owners ain't going to make it neccessary! :-)
Bob (robert) Midget Turbo

Graham,

There is no machining required to the hubs when using the tapered bearings. Just press in the outer races and assembly like any other tapered bearing setup. You even use the original seal for the inner bearing.
Martin

Bob,

Any chance you could post a scan of that engineering drawing you have.
David Billington

Thanks Martin, I thought there was a problem with the discs (rotors) not being centralised in the calipers, hence the need for machining the hubs.
Graham P

Dave I have got the documents saved as a PDF file, if you give me your email address I will gladly send the file to you. The documents were for RHP which as you will be aware no longer exist although they did become NSK who now have the records. I am trying to get a friend of mine who is a director of NSK to do us a write up about these bearings but he is playing hard to get. However he wants me to do some work to his MGA before we go to France so I hope I can bargain. :-)
Bob (robert) Midget Turbo

Bob,

djb[ at ]metal-srts[ dot ]co[ dot ]uk . Thanks in advance, I look forward to receiving the details.
David Billington

Bob,

Sorry noticed a mistype in the earlier post try

djb[ at ]metal-arts[ dot ]co[ dot ]uk .
David Billington

Bob,

Have you had the opportunity to send that bearing PDF file yet?. Sorry for the wrong email address previously.
David Billington

Just sent them Dave
Bob (robert) Midget Turbo

I thought there was an issue with weak stub axles. The spacer adds stiffening and support to the stub axle when it is clamped between the inner and outer bearings. If the spacer is removed when tapered rollers are fitted, doesn't this weaken the support provided to the stub axle?
Guy Weller

Guy
That is the theory. In reality, the clamping forces necessary to make a difference greatly exceed the ability of the threads involved, so there is no material strengthening of the stub axle. Please bear in mind that it is just as thick as the stub axle of a TR6 with rather less stress on it already. Also don't forget that the spacer is pretty trashy material.
David "no spacers" Lieb
David Lieb

David Lieb,

Have you done the engineering calcs to show the thread isn't strong enough to provide strengthening and in what way is the spacer trashy material. The spacer appears to be cast but that doesn't mean it is trashy, just cast, and cast iron, if the spacer is CI, is capable of taking high compressive loads which is what the spacers is doing as it can't take tensile load.
David Billington

Bob,

Thanks for the PDFs of the bearings. A quick look shows the general dimensions and contact angle of the LJT25 match Fafnir 7205W, and the MJT17 match Fafnir 7303W, what I haven't found for any angular contact bearings is the kicker in the RHP data, that 0.0mm to 0.025mm under gauging load of 24.5N spec for the race side alignment. Having said that now that detail is known a new set of bearings could be measured and the necessary compensation made to the spacer.
David Billington

David B,
Perhaps your British spacers are cast iron, but the ones they shipped to the USA are non-ferrous, quite light and not very strong.

No, I did not do the engineering studies, a Timken engineer did. If you are that fond of the strengthening myth, you are welcome to it. Here is Timken's response to the question regarding using the spacer for strength:

"In theory the spacer is clamped between two bearing inner races and effectively creates a shaft of a larger diameter. This theory is used on some Heavy Duty truck axles. The ability for this theory to work requires a high clamp load. In the Spridget design the ability to have a high clamp is limited by the small thread size. Basically the threads start to deform before you have a high enough clamp load applied."

David "works for me" Lieb
David Lieb

David Lieb,

I expect you're correct about the spacer not helping strengtening, and while I have an engineering degree I have better things to do with my time at the moment than analyse it. I checked the dims on a Ford Granada front stubaxle I have around and they are 29mm ID for the inner bearing and 17.5mm for the outer so not far off the 25mm and 17mm of the Spridget, also the Granada probably weighs twice as much if not more and that stubaxle is often used in GT40 replicas or was when more common.

I have heard of the stubaxles breaking, most likely in racing use, a larger radii at the base of the stubaxle would most likely help but no easy to achieve after manufacture. What made me say that was recently I was involved in some VW mods with Porsche bits and I noted that the inner bearing inner race on the VW and Porsche bearings had a much larger radius than a normal taper rollers.

May look into some taper rollers when it comes time to get the car back together.
David Billington

I have stressed my stub axles pretty well over the last five years or so that I have been autocrossing the car with taper rollers and no spacer. Granted, I am not running nearly so fast as the road racers, but I was having issues with driving it on two wheels for a while there, so I have to feel that the stresses were there ;-) At any rate, I have had no problems (until the next event, now that I opened my big mouth) with stub axles to date.
David "post hoc ergo what?" Lieb
David Lieb

I would like to pick up this subject again.
I have just rebuild my front and realized I have big play on my front hub despite new bearings.
It appears that the spacer is 38,2 mm long while the distance inside the hub between the bearings is only 37,7 mm - causing the bearing slightly to sepparate..
I am thinkink of shortening the space space by 7/10 mm to fix the problem - or mayby just leave out the spacer as suggested.

Has anyone had similar problem ?

Regards

Lars
Lars

Lars

There's a ton on this in the archive. I'f found the original bearings fit fine (i managed to buy a 70's packaged orig bearing; identified as the larger has a slim outer shell) but a more recent replacement on the other side was a nighmare. The cheaper bearings were all very rough with more play than the old one I took off. Eventually I bought one from Peter May, and a friend very kindly shaved 10 thou off the spacer and it's now fine.

I wouldn't take off 7/10 of a mm in one go; the worst situation you can have is the bearing becomes tight once you tighten up the stub axle nut.

I'd try .4 mm and try it; you can always remove more. (Eg. I measured ~15 thou play in mine, and chickened out and only had 10 thou removed and it was fine...)

A
anthony

This thread was discussed between 30/06/2008 and 19/07/2008

MG Midget and Sprite Technical index

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