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MG MGB Technical - Front wheel bearing problem

Hi, I have just changed the front nearside wheel bearing on my 1975 MGBGT.

The reason I changed it was that the brake calliper had seized on unbeknown to me.

The car has only done 29,000 miles and I have only owned it for three months - two of which it has been off the road having the interior refurbished.

Whilst it was not being driven I refurbished all the wheels one by one - they had begun to go rusty.I removed them, sandblasted each one, and re painted them with smooth Hammerite.

Having replaced the interior, the car ws looking very tidy and I was very proud of my handiwork. It being a nice day I decided to show it off to my 16yr old son.

After a short drive,(five miles) my son told me he could smell burning. Thinking this was just a MG smell I told him not to worry.

However after parking the car up, my son asked me to look at the wheel - which I did and saw that the newly painted wheel looked like it was melting.

I let the wheel cool down, took it off and could see that the brake calliper was the obvious cause. Looking at the wheel bearing I could see that the grease looked like it had gotten too hot too.

It looked like oil.

I ordered new callipers, bearings oil seals ect from MGOC - and set about replacing them.

I took the old hub off, sandblasted it clean, re painted it with calliper paint. I took the brake disc off and did the same - it looks like new.

I knocked the old races out, replaced them with new ones,re packed the bearings with High Melting Point grease, put them into the hub, tightened it all up to 70lbs - until the bearings just gripped (ala the haynes manual).

I then loosened them off put some shims in, re tightend things up and now cannot get any end play whatever.

The wheel turns fine, and feels okay - but there is no play at all.Despite putting lots of the seven thicknesses shims the MGOC supplied me with.

What have I done wrong? Has anyone else had this problem please?

Regards

Edd




E McGee

Edd,

Don't forget to find the reason for the caliper locking up (just a thought).

If the wheel is turning and there is no 'thunk' when you pull on the wheel it is possible that you have too much preload on the races of the bearings. If your trapazoidal bearing spacers are a bit short you may not have enough shims to play with.

If you have access to a dial indicator with a magnetic base, put the magnetic base on the brake disk, and the pin point of the indicator on the stub axle end. Measure the end float (total play from full in to full out of the hub assembly or wheel). If there isn't any, proceed as follows:

Measure your current stack of shims. Secure enough .030 shims to give you a stack that is thicker. For example, if your stack is .048, two .030 shims will give you a .060 total. Install these and check for endfloat. Subtract the total play in the dial indicator from .003 to get the new value. For example, if .060 gives you .005 endfloat, and .005-.003 is .002, you need a new shim set that will give you .058, or one .030, two .010, a .005 and a .003.

If you still don't have .002 to .003 endfloat with the .060 shims in the example, add a .010 shim and try again, using .070 as your new starting value.

Eventually you should be able to install enough shims to get to a 'thunk', but the dial indicator helps take out the ambiguity.

Alternatively, although it is a hassle, you could remove your spacers and measure them. They should be 1.575 or so thick. Less than that will require more than the .060 starting shims I mentioned above. Never hammer on the races or the spacers to remove any parts, the faces of the spacers need to be kept fresh.

Hope this helps,
dave
Dave Braun

You shouldn't have needed new bearings after such a relatively short drive, just repacking the outer bearing. I've had binding calipers on two cars, changed the calipers and discs (which you don't mention, but were almost certainly required if the wheel was as bad as you say), but just repacked the outer and checked the end-float. The inner bearing rarely needs it as grease naturally gravitates to the inner end being larger diameter. Having changed bearings in the past I have found the same shim set worked for both old and new, so came to the conclusion that they are primarily there to cater for small differences in the hub, spacer and spindle, the bearings themselves should be very close tolerance.

There is always one thick shim, plus as many of the three thicknesses of thinner shim as required. It's possible your thick shim got stuck to the old outer bearing inner race and was not refitted.
PaulH Solihull

I was always taught that the basic starting point for shims is 1mm + .010". Don't ask me why the millimetres and inches but it seems to work. Now I would recommend that you firstly assemble the hub dry (no grease) it becomes much easier to feel the end float and adjust the pack that way. You want .002" end float so for example if you have .005" remove the shim pack measure it's thickness and deduct .003" Remeasure the pack and put it all back together when you should have the specified .002" endfloat. Then dismantle the hub again and pack with grease and reassemble. At this point whilst you may not be able to realise the endfloat because of the grease the hub is correctly adjusted and should run freely.
Iain MacKintosh

Wiggle the hub (bearings ungreased) until you have two sets of shims 1 thou apart where the thicker gives just perceptible movement and the thinner doesn't. Use the thinner and add .002.
PaulH Solihull

Gentlemen, perhaps you have already answered some of my question which is threaded at MGB GT king pins. So Let me understand, what if we don't have any endfloat on wheel bearings? Presumably greater wear of the bearings, and a risk of running warm? but that depends on use right? So an occasional Jaunt, no high speed etc, or just looking at the car no problem? I only ask this because likewise, I have inspected the bearing, races look good shiny no scores but I could not detect endfloat.Car runs well with no nasty handling quirks, but wear I think in the svivel axle areas. any more comments? Mike
J.M. Doust

You can't be sure that your bearings aren't preloaded unless you have some end float in them. If they are then rapid wear will ensue. I would be inclined to add a two thou shim and see what the situation re end float is then.
Iain MacKintosh

Gents, thank you for your answers to the connundrum.

One question again please - if I strip the hub off the kingpin - remove the new (old) oil seal to get the bearing out - then put another one in it's place (ungreased) and likewise for the outer bearing.

Will I have to put the (new) oil seal on to preload the bearings or can I do it without the oil seal being in place?

Any advice please?

Edd
E McGee

Don't know why you are reluctant to put the seal in place. I've always done pre-load with the grease in anyway, but once the correct endfloat has been established grease can be introduced with the seal in place, a bit of grease on the seal is necessary. I also always check the end float after a few miles to see if it's increased any.
Mike, Play is there to allow things room to expand when they warm up. No end float could mean sieze up!! Not good. Too much will lead to rapid bearing wear.
Allan Reeling

Hi Guys,thank you for your advice - I am going to reassemble things as discussed and get on with the job.

Thank you all once again

Edd
E McGee

This thread was discussed between 16/05/2011 and 20/05/2011

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