CHECK YOUR BEARINGS II
by Jim Lunson
I mentioned last month the experience I recently had
with the front wheel bearings and that they needed adjustment. Here is
how I went about making the adjustments on my MG. First, remove the tire
and wheel and the cap over the hub end. Wire wheels do not have the cap
but the same nut inside the hub. Pull out the cotter pin and unscrew the
large slotted nut (1-1/8" dia). Behind the nut is a thick flat washer
with a tab on it and behind that is the outer bearing case. All these
need to be slid off the end of the shaft. Behind the bearing are shims,
looking like simple washers, but of varying thicknesses. They also need
to come off. They usually can be reached with your fingers and pulled
right off the shaft, but if they stick, a magnet part retriever works
great to lift them out off the shaft end. These washers come in .003,
.005, and .010 inch thicknesses. The bearing adjustment is made by
inserting as many washer shims as necessary to allow the wheel to spin
freely when the outer bearing and washer are replaced and the nut
tightened, but not so many shims as to cause wobble in the least, even
when the big end nut is very tight. The thickness of shims is fairly
easy to discern: the .010 shim is almost the thickness of a regular bolt
washer, the .050 half as thick as the .010, and the .003 shim is
flexible and about the thickness of paper. You will probably need a
couple of each .005 and .003 shims to do the job on one wheel.
My adjustment to the front wheel bearing on my car
went like this:
I removed the tire, cap, cotter pin, large nut, big
thick washer and the outer bearing set and behind the bearing, the
shims. On the innermost end of the shaft is a .010 shim, almost always
needed as the bearing tube spacer is cut short on purpose so shims are
always required. Outboard of this one was an .005 and 2 each .003 shims.
This made a total of .021 inch of shim on the shaft (.010 + .005 +
.006). I started by removing all but the .010 shim; replaced the
bearing, flat washer and tightened the end nut to the recommended 40
ft-lb torque setting. The wheel would not turn at all -
Removed the nut, washer and bearing assembly again,
and added a .050 shim on top of the .010 for a new total of .015 inch.
Replaced everything, tightened up the nut and still no turning the wheel
- still too tight.
Removed everything again, and added one .003 shim
for a new total of .018 shims on the shaft. Tightened up everything and
now had a free spinning wheel with just a slight wobble in the vertical
direction, better than before I started but not perfect.
Removed everything again, took out the .005 and the
.003, then inserted two .003 shims for a total of .016 inch. Tightened
up the big nut on the end once more and this was it. The wheel spun
freely, but with no wobble.
To complete the job, I put the torque wrench on the
big nut and increase the reading somewhat more until the slot in the nut
aligned with the hole in the shaft. Insert the cotter pin, cap and put
the tire back on. Check once again for wobble using the 6-12 o'clock
method again and for free spin. The wheel and tire assembly now had no
wobble and still turned freely. Job done. It is just a combination of
shims using the trial and error method to get a smooth spin yet no
wobble or play between the bearings.
Please note that this sequence is only for adjusting
the front bearings on an MG. Keep in mind that this operation is not a
complete bearing replacement job or overhaul, but only an adjustment.
The complete job is a bit more complicated as it involves removing the
brake caliper so the entire disk hub can be removed to get at the inner
bearing race. And during any renewal of these bearings, inspection for
wear is important and also to be sure to add lots of clean bearing
grease in the reassembly steps to insure they last and roll properly.
Nevertheless, it is amazing how much difference a thin shim can make in
the steering feel of the car and this method on the MG, if done properly
will yield many miles of trouble free rolling. So check the bearings, do
the exercise outlined above, and insure the wheel bearing fit properly
so they can do their job.