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MG MGB Technical - Shimming the hubs

Hi,
6,000 miles ago I fitted new front bearings. I got underneath the car tonight to grease her up and noticed that one of the wheels has play in it. There's no obvious movement in any of the suspension/kingpin area so I'm guessing I haven't shimmed it up correctly.

I knocked out the split pin and retourqued the hub but that didn't help. To get rid of the play will I have to add more shims or take some out? If I need extra shims I need to visit the part shop so there's no point opening up the brake lines until I actually have the parts for the job.

Thanks in advance,

Andy
Andy

1) You'll have to remove some. But you may need some shims anyway. For instance if you have to remove the play by .002", but the smallest shim now in the hub is .005" you'll probably want a few .001" to replace it with. Then again, I'd take it apart now anyway. You may get lucky and all you have to lose is another split pin.

2) Don't disconnect the brake hoses. Get a coat hanger, bend it into an 'S' shape. Hook one end over the shock absorber, hang the caliper on the other end. Adjust the coat hanger as neccessary to keep the caliper out of the way of other work.




Matt Kulka

Thanks for the quick response Matt. I'll go out and get some shims in the morning.

I have to break into the brake lines because I'm actually doing this to a C and there's no chance of moving the caliper without first removing the brake line.

I just knew I'd get a quicker response on here and the principle is the same.

Thanks again

Andy
Andy

I'm not sure how the set up on a C differs from the B, but when I shimmed my hubs I didn't need to remove the calipers at all - just took the pads out so there was no risk of them touching the disc while I changed the shims and checked the results.
Miles Banister

Miles,

You've got me thinking now. As I see it the main problem I have is persuading the existing shims to come out again now they are covered in grease.

I'm working on a wire wheel hub which means I'm working down the inside of a tube. I like the idea of removing the brake pads though. it might just give me the extra bit of flexibility I need.

I will give it a go tonight. I hate bleeding the brakes, mostly because I have visions of managing to spill the fluid on my paintwork.

Andy
Andy

Just a thought. This problem is very simple to correct on anything I have seen but MG's.
On other cars you remove the split pin tighten the hub nut to remove the play, back off the
nut to next split pin hole and insert a new split pin, done. Same type bearings, but MG's
use a spacer, shims and a torque wrench to do what is very simple on other cars. This
not an American thing, my Jensen Interceptor has the same type bearings but no spacers
or shims. I've said too much, follow the shop manual on your bearing adjustments to insure
you have the correct end float. Paul Hunt's web site tells you how.

Regards, Clifton
Clifton Gordon

Andy,
Hmm, it might be more difficult with the ww hub than it was with mine. With the hub nut removed my outer bearing and spacer just fell out and then I could pick out the shims using a very small screwdriver with a turned over end. I hope you can do it without having to bleed the brakes - I'm always worried about breaking off the nipple when I do that!
Miles.
Miles Banister

Andy,

To get the shims out, would a magnet work? I've got one on the back end of a screw starter - the whole thing is about the size and shape of a wooden pencil. Maybe you've got a small screwdriver with a magnet on the back. If not, an auto parts store would surely be able to sell you one cheap.

Matt Kulka

Hi Guys,

I removed the brake pads. This gave me enough lateral movement to unseat the inner bearing race and the shims. I searched around for a magnet but couldn't find one so i used a dentist's tool that he would use to descale your teeth. It worked a treat. I was able to use it to hook out the bearing and the shims.

I have discarded the thinnest shim and things seem to be OK now.

Andy
Andy

There must be some play or they are too tight, an end-float of .002 to .004 is required. The rule of thumb is to find two combinations of shims .001 apart - one that gives perceptible play and one that doesn't, then use the thinner stack plus a .003 (the thinnest shim).
Paul Hunt

clifton;
I gain more respect for you every time you type. I always toss the spacer and set them up like 99.9% of the cars in the world and have never had a problem. Bob
Bob Thompson

Bob
Are you suggesting that you can junk the spacer? Now that's got to be a worthwhile mod, for that will reduce the weight on the suspension making it operate better, and improve acceleration and economy. Why hasn't anybody else come up with this idea?
Pete

Just to add to the controversy, I'm with Bob, as I've mentioned multiple times in the last couple years. I've had no problems in years and I don't own a single spacer or shim.... Pete, you can't be serious about it increasing your economy though! :) You could also clean the rocks from your tire treads and gain as much weight savings I'd guess....

I would only add that you should service your bearings regularly if you run without spacers or shims. Do not let them get low on grease and risk seizing up! Just my opinion - advice is worth what you pay for it.
Roger
Roger Hotelling

I have been servicing MGBs for 30 years, so let me weigh in with a couple of thoughts about these front wheel bearings.

It is only necessary to grease the outer wheel bearing. Perhaps because of the larger diameter of the inner bearing, grease moves from the outer to the inner bearing. I've seen MGBs with dry outer wheel bearings -- so dry that the bearing froze and SNAPPED the stub axle! Yet, there was plenty of grease on that inner bearing. I would tell you that it's necessary to grease these bearings every 12,000 miles or every five years, whichever comes first.

Before removing the outer wheel bearing to grease it, first remove the split pin and then tighten the nut to about 60lb-ft. Then judge the resistance to turn. The front rotor should spin freely but have NO discernable end float -- it should NOT tunk when pulled in and out. If it tunks, you know you'll have to remove some shims; if it tightens up, you know you'll have to add some shims (or a spacer if the former mechanic has removed it entirely). The shims come in 0.030", 0.010", 0.005", and 0.003". The system "always" uses at least a 0.030" shim.

We use NGLI #2 grease.

It's not necessary to remove the caliper to grease the bearing. Simply remove the split pin, the nut (1 1/8"), the washer, the outer wheel bearing (shake the rotor, then pull it out with two right angled scribes, then the shims. Add or subtract shims, then fit the greased outer bearing to the stub axle, then the washer, and then the nut. Pull the nut down to that 60# torque and judge the end float (the tunk) and the ease of rotation.

Working with disc or ROstyle cars is easy; the wire wheeled cars can be a SOB. In fact, sometimes it is easier to simply unscrew the front nuts to shear the split pins. Both these nuts are common RH threads (the T types and MGAs have nuts that tighten in the direction of wheel rotation).

If you are fitting new bearings, set them up in oil and experiment with the shims. Here you want the rotor to spin freely and have a very tiny "tunk" which equals that 0.003" end float. Once you grease the bearings the rotor will still run free but the tunk will be gone. If you are fitting new bearings, be certain to polish that inner spacer (that rides against the hub seal) -- and, make certain there is a film of grease on that spacer so the hub seal does not have to run dry.

It is extremely rare to have to change wheel bearings.

A note about the importance of the spacer and shims. This stub axle "system" is incredibly strong because there is one shaft (the stub axle) tigthtened within a column (the inner spacer on which the seal rides, the inner race of the inner wheel bearing, the spacer, the shims, the inner race of the outer wheel bearing, and finally the washer that holds that column tight). This "system" is strong because it's under stress. I cannot remember having EVER seen a broken stub axle, so the stub axle is very durable by itself, but here is an excellent, durable system that will last the lifetime of the car. I believe it is folly to set these bearings up as "American."





John H Twist

John H Twist
all was going well until you contradicted yourself. Paragraph 2 I've seen MGBs with dry outer wheel bearings -- so dry that the bearing froze and SNAPPED the stub axle!
Paragraph I cannot remember having EVER seen a broken stub axle
Which one is correct?
Pete

Mr Twist,
I greatly respect your views as your MG ability is well known, but you say a 30 thou shim is always present. I have recently had my hubs in bits. One side had and needed a 30 thou, the other didn't. When I asked on this board about this, most correspondents who replied said they had never seen a 30 thou shim. What's the story? Incidentally, I set them up with the required end float just as you describe. I was interested that the grease slowly migrates to the inner bearing - not a lot of people know that.
Mike
Mike Howlett

I can see the logic in John Twist's arguement of the stub axle under tension being a strong unit but my logic runs slightly differently - the seal collar and the inner races of the bearings are not designed to rotate on the stub axle , they should remain stationary and the outer races, rollers and cages should be the only parts of the assembly to rotate with the hub. This can only be assured if the inner races, spacer and seal collar are locked up tight by the retainiong nut/shims. Omit the spacer and shims and then all are free to rotate - not a good engineering situation!
Chris Betson

Hmmm. George Kostanza would say, "True my friend, true, I can see how these statements would seem contradictory- to the unpracticed eye. However, . . ." I assumed John means that he has never seen a snapped stub axle on a car that was set up as per the book and lubricated, as opposed to the ones that were run dry and froze, then snapped- which they would probably have to do, if they froze and the fool driving the car did not stop as soon as the axle/bearing started to complain.
Ken R
Ken Rich

In my work as a power equipment engineer, we got into trouble when the bean conters made us go to the low bidder for a large turbine-generator repair, rather than the OEM. It is amazing how many engineered solutions are not apparent and another manufacturers "solution" just doesn't work.
B.J. Quartermaine

Shimmed my hubs last weekend. I found I did need at least a .030 in each side plus a few more thous. John's directions seems complete and accurate compared to the 10 others I read on this subject. -Thanks.
Brian Johnson

Gosh! In fact, I've only seen ONE snapped stub axle, and that one belonged to a 1974 Mirage MGB. The owner failed to grease the wheel bearings at his purchase of the car, and the axle snapped, from the outer bearing overheating, just at the point where the threads meet the larger diameter (which holds the outer wheel bearing). I have never seen an MGB stub axle crack any other place. We did have one, once, which was bent!

A reminder to us all to CAREFULLY re-read our technical postings!

John
John H Twist

This thread was discussed between 11/06/2002 and 19/06/2002

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