CHECK YOUR BEARINGS
Part I
I had a recent surprise with my MG
that turned out to be a good learning experience. Took my MG in for its
annual safety inspection as required by Virginia and failed. Seems the
inspector jacked up the right front tire, grabbed it at the 3 and 9
oclock positions, pulled on it and noticed some wobble. Needs new tie
rods he exclaimed and slapped the reject sticker on the windshield.
Back home I inspected his findings and sure enough,
by jacking up the right front wheel and pulling on the tire at the 3-9
positions, there was some wobble. But I noticed there was also the same
wobble when I grabbed the tire at the 6-12 oclock positions. Wobble in
the horizontal direction could mean the tie rods, but in the vertical
direction it would have nothing to do with the tie rods and instead
indicates wear in the front wheel bearing. I got to remembering that I
had completely rebuilt the front suspension when I first got the car,
but that was now almost 20 years and 35,000 miles ago, so it was time to
look at the bearings again.
The bearings in the MGB are very strong, but are of a
unique design. Most cars use a method of seating the front wheel
bearings by simply tightening the large slotted nut on the end of the
shaft until the bearing tapers are squeezed together on the shaft to the
point they restrict spinning, then back off the nut until free spin is
achieved and then back the nut off a little more to line up the slots in
the nut with the hole in the shaft and reinsert the cotter pin. This
setup works but only if the perfect adjustment occurs exactly at the
spot on the nut where the cotter pin can be inserted does this
adjustment method give a perfect fit. Otherwise a little play is always
present in the adjustment. Not an exact way to get the best fit with
wheel bearings and why bearing wear out.
Instead of this system, the MG bearings are adjusted
using a steel tube spacer and then inserting shims (washers of varying
thickness) over the shaft to adjust the spacing between the inner and
outer bearings to provide an exact tight firm fit. The adjustment with
these shims is made down to the .001 inch. The hub nut can then be
tightened very tight (40-70 ft-lbs) and locked in with a cotter pin
wherever it lines up. The system is firm and is adjusted precisely to
the space needed between the bearings allowing them to spin very
precisely with no play or wobble. This setup yields minimal wear to the
bearing over the miles. It is one of the best designs on the entire MG.
So remember, every so often check your front
bearings, and wobble in the vertical direction probably indicates there
are too many shims spacing the bearing sets too far apart allowing for
the wheel to move on the shaft in addition to spin. In my case, the
adjustment was good when done 20 years ago, but due to wear over the
miles, a new adjustment was necessary. Ill go in to the steps to make
the bearing adjustment in the next issue. Suffice to say that after
making corrections to these shims, I then checked the left tire, and
performed the same exercise. Then back to the inspection station and
passed. No wobble whatsoever. And no work was needed on the tie rods or
steering system either.
I usually fear the annual Virginia safety inspection
and have thought about switching to the antique plate which eliminates
this hassle, but I havent done it as the inspection does serve a
purpose as demonstrated by this little episode. An added benefit to this
incident over and above a safety issue is that I noticed as I drove back
to the inspection station the car seemed to roll easier, truer and the
steering felt like I had rebuilt the entire front end again. Amazing how
the gradual wearing goes so unnoticed. So dont wait for an inspection,
check your bearings sometime, and make sure you dont have any wobble in
the vertical direction. And dont panic if you get rejected some time at
your friendly inspection station for front wheel wobble. If its in the
vertical direction, it can usually be easily adjusted.