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MG MGB Technical - Front bearing shims experience?

67 BGT with new parts..... I am setting up the end float as per the manual and John Twist's video on the correct shim determination and so far I am up to 5 of various thickness and a couple are the thicker type and am surprised to see so many. I think I had a 10, 5 and 3 before the new stuff. Anyone have similar experience with new stuff? I set up the intial install without any and did the torque down past 60 pds to seat the new races before installing the shims. Seems like more than usual. Thanks Ralph
R Stegs

There is normally one thick (25 thou) shim and a couple of 3 or 5 thou ones.

If the stub axle was reconditioned, they often sand blast the unit which leaves a rough surface for the bearings to sit on - this should be polished with fine emery paper or the bearings will stick on the shaft.

If the hubs are new then that will affect the number of shims as it is the distance between bearing seats that determines the number of shims needed.

I hope you span the bearings while initially tightening without shims!
Chris at Octarine Services

Ralph. Since no one has answered yet, let me take a shot at it.

The bearing races should be installed using a special tool that will firmly seat them into the hubs. I took my hubs over to a friend, who is a professional mechanic, and used his tool the last time that I did this job. Prior to that time I used a large steel bar to install the races which seemed to work fairly well, but the proper tool works much better. If using something other than a bearing race installation tool you need to make absolutely sure that the races are fully seated against the internal shoulders in the hub. If you can get a finger nail between the race and the shoulder, the race is not fully seated. A dental pick might also work for this check and might be easier to use, but I have not tried this yet.

I realize the workshop manual mentions tightening the stub axle nut to fully seat the bearing races, but I have some doubts about that method. Considering the amount of force necessary to seat the races fully, I suspect that you have a better chance of damaging the roller bearings than seating the races if using the factory method.

The rest of the factory method I do agree with. Paul Hunt has a good tech article on installing wheel bearings on his "The Pages of Bee and Vee". Paul suggests that one can set the end float by feel. But, that method did not work for me when I tried it. I spent two hours trying to set it that way, then gave up and got a dial indicator (clock gauge) out of the shop along with a slab of steel to attach the magnetic base to. (Dial indicators can be had, at a very reasonable price, from J&L Industrial or ENCO, often on sale with a magnetic base having an adjustable arm system making it perfect for automotive use.) Using the dial indicator, it took me about ten minutes to set the end float correctly. Knowing what shims you have in the system already, and knowing what the actual end float is, quickly allows you to assemble a shim pack that will work with your axles.

So, make sure that the races are fully seated in the hubs. If not, there will be excessive shimming required. (Harbor freight may have a tool for installing the races if you do not know anyone who would be willing to let you use theirs, or would be willing to seat the races for a reasonable price.) Ensuring the races are fully seated is the first step in seeing if there is really a problem or not.

The second step is to remove the entire shim pack and check the end float using a dial indicator. Based on the reading you get from that, put together a shim pack that will give you the specified end float (.002" to .004"). Install the shim pack and torque the nut to 40 lbft, the minimum specified torque and again take a reading using your dial indicator. If all goes well, you will be within specifications. If not, you can add or subtract shims from the pack to obtain the proper reading.

Les
Les Bengtson

Thanks for the information. I cleaned up the stub and FULLY seated the bearing races and three usual shims did the trick! Ralph
R Stegs

Les,

"The second step is to remove the entire shim pack and check the end float using a dial indicator"

Nope - if you take out all the shims there will be no end float to measure.

Normally I would put in 50 thou of shims and torque up, measure the end float at say 10 thou, take out the 50 thou of shims and replace with 50 - 10 +2 = 42 thou of shims to get a 2 thou end float.
Chris at Octarine Services

If you don't have a dial gauge simply juggle shims until there is just detectable play with one combination and no play with a combination .001 smaller, then use this smaller combination plus another .003 and that will put you in the correct range of .002 to .004.
Paul Hunt

Chris. You are perfectly correct. Should have re-read the posting knowing that I was tired and caught that point myself. Thanks.

Les
Les Bengtson

what Paul said
Peter

I do the same as Paul most of the time, but I wouldn't recommend setting end float by feel until you've done a number of them. In short, if while rocking the wheel by the tire you think there is a little play but you're not sure, it's probably spot on.
Steve Simmons

This thread was discussed between 02/04/2009 and 05/04/2009

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